:root {
  --ink: #132321;
  --muted: #61716e;
  --subtle: #eef4f1;
  --line: #d9e6e2;
  --paper: #ffffff;
  --paper-soft: #f8fbfa;
  --teal: #0f766e;
  --teal-2: #21a58f;
  --blue: #3b74d7;
  --amber: #d88a16;
  --rose: #cf4d68;
  --violet: #7357c9;
  --shadow: 0 24px 60px rgba(26, 53, 49, 0.12);
  --soft-shadow: 0 12px 34px rgba(26, 53, 49, 0.08);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: 112px;
}

body {
  margin: 0;
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  background:
    linear-gradient(180deg, rgba(248, 251, 250, 0.96), rgba(248, 251, 250, 0.96)),
    repeating-linear-gradient(90deg, transparent 0 64px, rgba(15, 118, 110, 0.035) 64px 65px);
  line-height: 1.65;
}

body.modal-lock {
  overflow: hidden;
}

html.modal-lock {
  overflow: hidden;
}

.home-landing-page {
  min-height: 100vh;
  overflow: hidden;
  background: #eef7f4;
}

.home-landing-page .reading-progress {
  display: none;
}

.home-landing {
  position: relative;
  display: grid;
  min-height: 100vh;
  place-items: center;
  padding: clamp(32px, 6vw, 72px);
  overflow: hidden;
  background:
    linear-gradient(180deg, rgba(244, 250, 248, 0.22), rgba(235, 246, 243, 0.84)),
    linear-gradient(90deg, rgba(240, 248, 246, 0.96) 0%, rgba(240, 248, 246, 0.62) 48%, rgba(240, 248, 246, 0.9) 100%),
    url("../assets/compulsory1-hero-photo.jpg") center center / cover no-repeat;
  isolation: isolate;
}

.home-landing::before {
  position: absolute;
  inset: -18%;
  z-index: -2;
  content: "";
  background:
    linear-gradient(105deg, transparent 12%, rgba(255, 255, 255, 0.6) 31%, transparent 48%),
    repeating-linear-gradient(118deg, rgba(15, 118, 110, 0.08) 0 1px, transparent 1px 86px);
  opacity: 0.72;
  transform: translateX(-8%);
  animation: homeLightSweep 12s ease-in-out infinite alternate;
}

.home-landing::after {
  position: absolute;
  inset: 0;
  z-index: -1;
  content: "";
  background:
    radial-gradient(ellipse at 50% 56%, rgba(255, 255, 255, 0.26), transparent 48%),
    linear-gradient(180deg, rgba(255, 255, 255, 0.24), rgba(235, 246, 243, 0.58));
  backdrop-filter: blur(1px);
}

.home-motion-canvas,
.home-lab-veil {
  position: absolute;
  inset: 0;
  pointer-events: none;
}

.home-motion-canvas {
  z-index: 4;
  display: block;
  width: 100%;
  height: 100%;
  opacity: 0.72;
  mix-blend-mode: multiply;
}

.home-lab-veil {
  z-index: 1;
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.08), rgba(235, 246, 243, 0.28)),
    repeating-linear-gradient(0deg, rgba(19, 35, 33, 0.03) 0 1px, transparent 1px 52px);
  mask-image: linear-gradient(180deg, transparent, #000 16%, #000 84%, transparent);
}

.home-entry-grid {
  position: relative;
  z-index: 2;
  display: grid;
  width: min(100%, 1030px);
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: clamp(12px, 1.8vw, 18px);
}

.home-entry-card {
  position: relative;
  min-height: clamp(150px, 20vh, 180px);
  padding: clamp(22px, 3.2vw, 34px);
  overflow: hidden;
  border: 1px solid rgba(180, 216, 209, 0.9);
  border-radius: 8px;
  color: var(--ink);
  background:
    linear-gradient(135deg, rgba(255, 255, 255, 0.92), rgba(255, 255, 255, 0.72)),
    radial-gradient(circle at var(--mx, 50%) var(--my, 50%), rgba(15, 118, 110, 0.12), transparent 34%);
  box-shadow: 0 24px 70px rgba(26, 53, 49, 0.13);
  backdrop-filter: blur(18px) saturate(132%);
  transform: translate3d(0, 0, 0);
  transition: transform 220ms ease, border-color 220ms ease, box-shadow 220ms ease, background 220ms ease;
}

.home-entry-card::before {
  position: absolute;
  inset: 0;
  content: "";
  border-radius: inherit;
  background: linear-gradient(115deg, transparent 0%, rgba(255, 255, 255, 0.86) 42%, transparent 64%);
  opacity: 0;
  transform: translateX(-38%);
  transition: opacity 220ms ease, transform 620ms ease;
}

.home-entry-card::after {
  position: absolute;
  inset: 0;
  content: "";
  border-radius: inherit;
  padding: 1px;
  background: linear-gradient(120deg, rgba(15, 118, 110, 0.62), rgba(59, 116, 215, 0.42), rgba(216, 138, 22, 0.42), rgba(15, 118, 110, 0.62));
  opacity: 0;
  -webkit-mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
  -webkit-mask-composite: xor;
  mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
  mask-composite: exclude;
  pointer-events: none;
  transition: opacity 220ms ease;
}

.home-entry-card:hover,
.home-entry-card:focus-visible {
  border-color: rgba(15, 118, 110, 0.34);
  box-shadow: 0 34px 86px rgba(15, 72, 68, 0.18);
  transform: translateY(-6px) scale(1.01);
}

.home-entry-card:hover::before,
.home-entry-card:focus-visible::before {
  opacity: 0.88;
  transform: translateX(34%);
}

.home-entry-card:hover::after,
.home-entry-card:focus-visible::after {
  opacity: 1;
}

.home-entry-card-disabled {
  cursor: not-allowed;
  border-color: rgba(174, 192, 188, 0.72);
  color: #71817e;
  background: rgba(244, 248, 247, 0.72);
  box-shadow: 0 16px 42px rgba(26, 53, 49, 0.07);
  filter: saturate(0.62);
}

.home-entry-card-disabled:hover {
  border-color: rgba(174, 192, 188, 0.72);
  box-shadow: 0 16px 42px rgba(26, 53, 49, 0.07);
  transform: none;
}

.home-entry-card-disabled::before,
.home-entry-card-disabled::after {
  display: none;
}

.home-entry-card-disabled span {
  color: #71817e;
}

.home-entry-card-disabled strong {
  color: #91a09d;
}

.home-entry-card span,
.home-entry-card strong {
  position: relative;
  z-index: 1;
  display: block;
}

.home-entry-card span {
  margin-bottom: 10px;
  color: var(--ink);
  font-size: clamp(25px, 3vw, 31px);
  font-weight: 950;
  line-height: 1.18;
}

.home-entry-card strong {
  max-width: 30em;
  color: #526561;
  font-size: clamp(15px, 1.5vw, 17px);
  font-weight: 850;
  line-height: 1.65;
}

.book-cover-page {
  overflow: hidden;
  color: #f5f2e9;
  background: #090a08;
}

.book-cover-page .home-landing {
  align-items: center;
  min-height: 100vh;
  padding: clamp(28px, 4vw, 58px) clamp(20px, 5vw, 70px) clamp(30px, 4vw, 60px) clamp(86px, 10vw, 150px);
  background:
    linear-gradient(180deg, rgba(9, 10, 8, 0.46), rgba(9, 10, 8, 0.94) 76%),
    linear-gradient(116deg, rgba(16, 113, 104, 0.24), transparent 38%, rgba(202, 128, 25, 0.18) 76%, transparent),
    #090a08;
}

.book-cover-page .home-landing::before {
  inset: 0;
  z-index: -2;
  background:
    linear-gradient(90deg, rgba(255, 255, 255, 0.045) 0 1px, transparent 1px 92px),
    linear-gradient(0deg, rgba(255, 255, 255, 0.035) 0 1px, transparent 1px 72px);
  opacity: 0.42;
  transform: none;
  animation: none;
}

.book-cover-page .home-landing::after {
  z-index: -1;
  background:
    linear-gradient(180deg, transparent 0%, rgba(0, 0, 0, 0.36) 48%, rgba(0, 0, 0, 0.88) 100%),
    linear-gradient(90deg, rgba(9, 10, 8, 0.86), transparent 28%, transparent 72%, rgba(9, 10, 8, 0.82));
  backdrop-filter: none;
}

.book-cover-page .home-motion-canvas {
  opacity: 0.52;
  mix-blend-mode: screen;
}

.book-cover-page .home-lab-veil {
  background:
    linear-gradient(180deg, rgba(245, 242, 233, 0.04), transparent 30%, rgba(245, 242, 233, 0.03)),
    repeating-linear-gradient(0deg, rgba(245, 242, 233, 0.05) 0 1px, transparent 1px 58px);
  opacity: 0.56;
  mask-image: linear-gradient(90deg, transparent, #000 12%, #000 92%, transparent);
}

.book-cover-hero {
  position: relative;
  z-index: 2;
  display: grid;
  width: min(100%, 1280px);
  gap: clamp(18px, 2.4vw, 30px);
}

.book-cover-title {
  width: min(100%, 760px);
  margin-inline: auto;
  text-align: center;
}

.book-cover-title span {
  display: inline-flex;
  align-items: center;
  min-height: 28px;
  padding: 3px 10px;
  border: 1px solid rgba(245, 242, 233, 0.22);
  color: rgba(245, 242, 233, 0.76);
  font-size: 13px;
  font-weight: 800;
  line-height: 1;
  background: rgba(245, 242, 233, 0.08);
}

.book-cover-title h1 {
  margin: 12px 0 0;
  color: #fffdf5;
  font-size: clamp(44px, 8vw, 96px);
  font-weight: 950;
  line-height: 0.98;
  text-shadow: 0 12px 42px rgba(0, 0, 0, 0.52);
}

.book-rail {
  position: fixed;
  top: 50%;
  left: clamp(16px, 2.2vw, 28px);
  z-index: 4;
  display: grid;
  gap: 8px;
  width: 58px;
  transform: translateY(-50%);
}

.book-rail a {
  display: grid;
  min-height: 48px;
  place-items: center;
  border: 1px solid rgba(245, 242, 233, 0.15);
  border-radius: 8px;
  color: rgba(245, 242, 233, 0.7);
  font-size: 12px;
  font-weight: 850;
  line-height: 1.1;
  text-align: center;
  background: rgba(18, 21, 19, 0.62);
  box-shadow: 0 12px 28px rgba(0, 0, 0, 0.22);
  backdrop-filter: blur(16px);
  transition: color 180ms ease, border-color 180ms ease, background 180ms ease, transform 180ms ease;
}

.book-rail a:hover,
.book-rail a:focus-visible {
  border-color: rgba(209, 143, 48, 0.62);
  color: #fffdf5;
  background: rgba(84, 62, 28, 0.54);
  transform: translateX(3px);
}

.book-shelf {
  --book-width: clamp(196px, 18vw, 252px);
  --book-overlap: clamp(-104px, -7vw, -72px);
  position: relative;
  display: flex;
  align-items: end;
  justify-content: center;
  min-height: clamp(430px, 60vh, 600px);
  padding: clamp(72px, 9vh, 104px) 34px clamp(50px, 6vw, 76px);
}

.book-shelf::before {
  position: absolute;
  right: -2%;
  bottom: 18px;
  left: -2%;
  height: clamp(52px, 8vw, 86px);
  content: "";
  background:
    linear-gradient(180deg, rgba(245, 242, 233, 0.18), rgba(245, 242, 233, 0.04) 8px, rgba(0, 0, 0, 0.6) 46%, transparent),
    linear-gradient(90deg, transparent, rgba(209, 143, 48, 0.3) 24%, rgba(16, 113, 104, 0.22) 62%, transparent);
  transform: rotateX(67deg);
  transform-origin: bottom center;
  filter: blur(0.2px);
}

.book-shelf::after {
  position: absolute;
  right: 5%;
  bottom: 42px;
  left: 5%;
  height: 28px;
  content: "";
  background: linear-gradient(90deg, transparent, rgba(0, 0, 0, 0.76), transparent);
  filter: blur(16px);
}

.book-card {
  --book-angle: -78deg;
  --book-thickness: 20px;
  --neighbor-shift: 0px;
  position: relative;
  z-index: calc(10 + var(--i));
  display: grid;
  width: var(--book-width);
  flex: 0 0 auto;
  margin: 0;
  color: #fffdf5;
  perspective: 2200px;
  perspective-origin: center center;
  transform: translateX(var(--neighbor-shift));
  transition:
    transform 560ms cubic-bezier(0.2, 0.82, 0.2, 1),
    z-index 0s linear 520ms;
}

.book-card + .book-card {
  margin-left: var(--book-overlap);
}

@media (hover: hover) {
  .book-shelf:hover .book-card:not(:hover) .book-visual img {
    filter: brightness(0.48) saturate(0.68);
  }

  .book-shelf:has(.book-card:is(:hover, :focus, :focus-visible))
    .book-card:has(~ .book-card:is(:hover, :focus, :focus-visible)) {
    --neighbor-shift: -42px;
  }

  .book-card:is(:hover, :focus, :focus-visible) ~ .book-card {
    --neighbor-shift: 42px;
  }
}

.book-card:hover,
.book-card:focus,
.book-card:focus-visible {
  z-index: 60;
  outline: none;
  transform: translate(4px, -58px) scale(1.04);
  transition:
    transform 560ms cubic-bezier(0.2, 0.82, 0.2, 1),
    z-index 0s;
}

.book-visual {
  position: relative;
  display: block;
  aspect-ratio: 1125 / 1600;
  transform: rotateY(var(--book-angle));
  transform-origin: center center;
  transform-style: preserve-3d;
  transition: transform 560ms cubic-bezier(0.2, 0.82, 0.2, 1);
}

.book-card:hover .book-visual,
.book-card:focus .book-visual,
.book-card:focus-visible .book-visual {
  transform: rotateY(-32deg);
}

.book-visual::before {
  position: absolute;
  inset: 0 auto 0 0;
  z-index: 3;
  width: 11%;
  content: "";
  border-radius: 5px 0 0 5px;
  background: linear-gradient(90deg, rgba(0, 0, 0, 0.48), rgba(255, 255, 255, 0.12) 44%, transparent);
  mix-blend-mode: multiply;
  pointer-events: none;
  transform: translateZ(calc(var(--book-thickness) / 2 + 2px));
}

.book-visual::after {
  position: absolute;
  inset: 0;
  z-index: 2;
  content: "";
  border: 1px solid rgba(255, 255, 255, 0.34);
  border-radius: 5px;
  background:
    linear-gradient(90deg, rgba(0, 0, 0, 0.42), rgba(255, 255, 255, 0.1) 8%, transparent 18%),
    linear-gradient(112deg, rgba(255, 255, 255, 0.2), transparent 26%, transparent 70%, rgba(255, 255, 255, 0.08)),
    radial-gradient(circle at var(--mx, 50%) var(--my, 40%), rgba(255, 255, 255, 0.22), transparent 34%);
  opacity: 0.58;
  pointer-events: none;
  transform: translateZ(calc(var(--book-thickness) / 2 + 2px));
}

.book-pages {
  position: absolute;
  top: -7px;
  bottom: 75px;
  left: calc(50% + 10px);
  z-index: 4;
  display: block;
  width: var(--book-thickness);
  border: 1px solid rgba(117, 105, 78, 0.72);
  border-left: 0;
  background:
    repeating-linear-gradient(180deg, rgba(82, 70, 49, 0.22) 0 1px, transparent 1px 4px),
    linear-gradient(90deg, #b9ad90 0%, #f5efd9 14%, #fffaf0 78%, #c4b99f 100%);
  box-shadow:
    inset -4px 0 rgba(74, 62, 43, 0.16),
    12px 16px 24px rgba(0, 0, 0, 0.34);
  transition: left 560ms cubic-bezier(0.2, 0.82, 0.2, 1);
}

.book-card:hover .book-pages,
.book-card:focus .book-pages,
.book-card:focus-visible .book-pages {
  left: calc(100% - 20px);
}

.book-pages::before {
  position: absolute;
  inset: 0;
  content: "";
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.42), transparent 3%, transparent 96%, rgba(68, 57, 38, 0.24)),
    repeating-linear-gradient(180deg, transparent 0 5px, rgba(74, 62, 43, 0.14) 5px 6px);
  pointer-events: none;
}

.book-pages::after {
  position: absolute;
  top: -2px;
  right: -3px;
  bottom: -2px;
  width: 4px;
  content: "";
  background: linear-gradient(180deg, #3b372f, #746c5a 48%, #2d2a24);
  box-shadow: 1px 0 rgba(255, 255, 255, 0.16);
}

.book-back {
  position: absolute;
  inset: 0;
  z-index: 0;
  display: block;
  border: 1px solid rgba(202, 190, 158, 0.46);
  border-radius: 5px;
  background:
    linear-gradient(90deg, rgba(30, 28, 24, 0.92), rgba(112, 104, 85, 0.9) 16%, rgba(53, 49, 41, 0.94));
  box-shadow: 16px 22px 34px rgba(0, 0, 0, 0.42);
  backface-visibility: visible;
  transform: translateZ(calc(var(--book-thickness) / -2));
}

.book-visual img {
  position: relative;
  z-index: 1;
  display: block;
  width: 100%;
  height: 100%;
  border-radius: 5px;
  object-fit: cover;
  filter: brightness(0.78) saturate(0.88);
  box-shadow:
    0 34px 70px rgba(0, 0, 0, 0.48),
    0 16px 28px rgba(0, 0, 0, 0.3);
  backface-visibility: hidden;
  transform: translateZ(calc(var(--book-thickness) / 2));
  transition: filter 320ms ease;
}

.book-card:hover .book-visual img,
.book-card:focus .book-visual img,
.book-card:focus-visible .book-visual img {
  filter: brightness(1) saturate(1.04) contrast(1.02);
}

.book-caption {
  display: grid;
  min-height: 64px;
  margin-top: 14px;
  gap: 4px;
  place-items: center;
  opacity: 0;
  text-align: center;
  text-shadow: 0 8px 24px rgba(0, 0, 0, 0.62);
  transform: translateY(8px);
  transition: opacity 240ms ease, transform 320ms ease;
}

.book-card:hover .book-caption,
.book-card:focus .book-caption,
.book-card:focus-visible .book-caption {
  opacity: 1;
  transform: translateY(0);
}

.book-caption strong {
  font-size: clamp(15px, 1.4vw, 18px);
  font-weight: 920;
  line-height: 1.22;
}

.book-caption em {
  color: rgba(245, 242, 233, 0.66);
  font-size: 12px;
  font-style: normal;
  font-weight: 760;
  line-height: 1.2;
}

.roadmap-card-pending {
  border-color: rgba(217, 230, 226, 0.74);
  background:
    linear-gradient(135deg, rgba(255, 255, 255, 0.9), rgba(248, 251, 250, 0.72)),
    repeating-linear-gradient(135deg, rgba(15, 118, 110, 0.045) 0 1px, transparent 1px 12px);
}

.reading-progress {
  position: fixed;
  top: 0;
  left: 0;
  z-index: 220;
  width: 100%;
  height: 3px;
  background: linear-gradient(90deg, var(--teal), var(--blue), var(--amber));
  box-shadow: 0 0 18px rgba(15, 118, 110, 0.26);
  transform: scaleX(var(--scroll-progress, 0));
  transform-origin: left center;
  pointer-events: none;
}

a {
  color: inherit;
  text-decoration: none;
}

button,
input {
  font: inherit;
}

button {
  cursor: pointer;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 28px;
  min-height: 76px;
  padding: 14px clamp(18px, 5vw, 76px);
  border-bottom: 1px solid rgba(217, 230, 226, 0.9);
  background: rgba(248, 251, 250, 0.92);
  backdrop-filter: blur(18px);
  transition: box-shadow 180ms ease, background 180ms ease;
}

body.has-scrolled .site-header {
  background: rgba(248, 251, 250, 0.96);
  box-shadow: 0 12px 32px rgba(26, 53, 49, 0.08);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  min-width: max-content;
  font-weight: 850;
}

.brand-mark {
  display: grid;
  width: 48px;
  height: 38px;
  place-items: center;
  border-radius: 8px;
  color: #fff;
  background: linear-gradient(135deg, var(--teal), var(--blue));
  font-size: 13px;
  font-weight: 900;
}

.nav-toggle {
  display: none;
  min-height: 40px;
  padding: 0 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  color: var(--ink);
  background: var(--paper);
  font-weight: 800;
}

.site-nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: 8px;
  color: var(--muted);
  font-size: 15px;
}

.site-nav a {
  position: relative;
  padding: 8px 12px;
  border-radius: 8px;
}

.site-nav a::after {
  position: absolute;
  right: 12px;
  bottom: 4px;
  left: 12px;
  height: 2px;
  border-radius: 999px;
  background: linear-gradient(90deg, var(--teal), var(--blue));
  opacity: 0;
  transform: scaleX(0.35);
  transition: opacity 160ms ease, transform 180ms ease;
  content: "";
}

.site-nav a:hover,
.site-nav a.active {
  color: var(--teal);
  background: rgba(15, 118, 110, 0.08);
}

.site-nav a:hover::after,
.site-nav a.active::after {
  opacity: 1;
  transform: scaleX(1);
}

.learning-hub {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1px;
  margin: 0 clamp(18px, 5vw, 76px);
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--line);
  box-shadow: var(--soft-shadow);
}

.learning-hub a {
  position: relative;
  min-height: 150px;
  padding: 22px;
  background: var(--paper);
  transition: transform 180ms ease, box-shadow 180ms ease, background 180ms ease;
}

.learning-hub a:hover {
  transform: translateY(-2px);
  background: linear-gradient(180deg, #fff, #f4fbf8);
  box-shadow: inset 0 0 0 1px rgba(15, 118, 110, 0.16);
}

.learning-hub span {
  display: inline-grid;
  width: 38px;
  height: 32px;
  margin-bottom: 16px;
  place-items: center;
  border-radius: 8px;
  color: #fff;
  background: var(--teal);
  font-size: 13px;
  font-weight: 900;
}

.learning-hub strong {
  display: block;
  margin-bottom: 8px;
  font-size: 20px;
}

.learning-hub p {
  margin-bottom: 0;
  color: var(--muted);
}

.hero {
  display: grid;
  grid-template-columns: minmax(0, 0.88fr) minmax(420px, 1.12fr);
  gap: clamp(28px, 5vw, 76px);
  align-items: center;
  min-height: calc(100vh - 76px);
  padding: clamp(42px, 7vw, 96px) clamp(18px, 5vw, 76px) 44px;
  overflow: hidden;
}

.hero-copy {
  max-width: 760px;
}

.eyebrow,
.panel-label {
  margin: 0 0 10px;
  color: var(--teal);
  font-size: 13px;
  font-weight: 900;
  letter-spacing: 0;
  text-transform: uppercase;
}

h1,
h2,
h3,
p {
  margin-top: 0;
}

h1 {
  margin-bottom: 22px;
  font-size: clamp(42px, 6vw, 78px);
  line-height: 1.04;
}

h2 {
  margin-bottom: 14px;
  font-size: clamp(28px, 4vw, 46px);
  line-height: 1.14;
}

h3 {
  margin-bottom: 10px;
  font-size: 22px;
  line-height: 1.24;
}

.hero-lede,
.page-hero p,
.section-copy p,
.module-card p,
.path-card p,
.knowledge-card p,
.equation-item p,
.exam-card p,
.lab-panel p,
.tracker-box,
.quiz-result {
  color: var(--muted);
}

.hero-lede {
  max-width: 650px;
  font-size: clamp(17px, 2vw, 21px);
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
  margin-top: 30px;
}

.primary-action,
.secondary-action {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 50px;
  padding: 0 22px;
  border-radius: 8px;
  font-weight: 850;
}

.primary-action {
  color: #fff;
  background: var(--teal);
  box-shadow: 0 14px 26px rgba(15, 118, 110, 0.2);
}

.secondary-action {
  border: 1px solid var(--line);
  background: #fff;
}

.dashboard-visual {
  position: relative;
  min-height: 520px;
}

.dashboard-visual img {
  display: block;
  width: min(100%, 740px);
  margin-left: auto;
  border: 1px solid rgba(217, 230, 226, 0.8);
  border-radius: 18px;
  box-shadow: var(--shadow);
}

.floating-panel {
  position: absolute;
  width: min(280px, 44%);
  padding: 16px;
  border: 1px solid rgba(217, 230, 226, 0.92);
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.94);
  box-shadow: var(--soft-shadow);
}

.floating-panel span {
  display: block;
  color: var(--muted);
  font-size: 13px;
  font-weight: 800;
}

.floating-panel strong {
  display: block;
  margin-top: 4px;
  font-size: 20px;
  line-height: 1.3;
}

.panel-progress {
  right: 5%;
  bottom: 18px;
}

.panel-formula {
  left: 3%;
  top: 28px;
}

.progress-track {
  height: 8px;
  margin-top: 12px;
  overflow: hidden;
  border-radius: 999px;
  background: var(--subtle);
}

.progress-track span {
  display: block;
  width: 0%;
  height: 100%;
  border-radius: inherit;
  background: linear-gradient(90deg, var(--teal), var(--amber));
}

.metric-strip {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1px;
  margin: 0 clamp(18px, 5vw, 76px);
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 16px;
  background: var(--line);
  box-shadow: var(--soft-shadow);
}

.metric-strip article {
  min-height: 132px;
  padding: 24px;
  background: var(--paper);
}

.metric-strip strong {
  display: block;
  font-size: clamp(30px, 4vw, 46px);
  line-height: 1;
}

.metric-strip span {
  display: block;
  margin-top: 10px;
  color: var(--muted);
  font-weight: 800;
}

.section {
  padding: clamp(58px, 9vw, 112px) clamp(18px, 5vw, 76px);
  scroll-margin-top: 112px;
}

.compact-section {
  padding-top: clamp(36px, 5vw, 58px);
}

.section-head,
.section-copy {
  max-width: 800px;
}

.feature-band {
  background: linear-gradient(180deg, rgba(238, 246, 243, 0.78), rgba(248, 251, 250, 0.96));
}

.path-grid,
.module-grid,
.knowledge-grid,
.exam-grid,
.syllabus-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
  margin-top: 30px;
}

.module-grid {
  grid-template-columns: repeat(5, 1fr);
}

.path-card,
.module-card,
.quiz-box,
.tracker-box,
.knowledge-card,
.equation-item,
.exam-card,
.lab-panel,
.safety-grid article,
.syllabus-grid article,
.question-card {
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--paper);
  box-shadow: var(--soft-shadow);
}

.spotlight-card {
  position: relative;
  isolation: isolate;
  overflow: hidden;
  transition:
    transform 180ms ease,
    border-color 180ms ease,
    box-shadow 180ms ease,
    background 180ms ease;
}

.spotlight-card::before {
  position: absolute;
  inset: 0;
  z-index: -1;
  background:
    radial-gradient(
      circle at var(--mx, 50%) var(--my, 30%),
      rgba(33, 165, 143, 0.16),
      rgba(59, 116, 215, 0.08) 30%,
      transparent 58%
    );
  opacity: 0;
  transition: opacity 180ms ease;
  content: "";
}

.spotlight-card:hover {
  border-color: rgba(15, 118, 110, 0.32);
  box-shadow: 0 24px 54px rgba(26, 53, 49, 0.13);
  transform: translateY(-3px);
}

.spotlight-card:hover::before {
  opacity: 1;
}

.reveal-ready .reveal {
  opacity: 0;
  filter: blur(4px);
  transform: translateY(18px);
  transition:
    opacity 520ms ease,
    filter 520ms ease,
    transform 520ms cubic-bezier(0.2, 0.78, 0.2, 1);
  transition-delay: min(calc(var(--reveal-index, 0) * 42ms), 220ms);
}

.reveal-ready .reveal.is-visible {
  opacity: 1;
  filter: blur(0);
  transform: translateY(0);
}

.path-card,
.module-card,
.quiz-box,
.tracker-box,
.knowledge-card,
.exam-card,
.lab-panel,
.syllabus-grid article,
.question-card {
  padding: 26px;
}

.path-card {
  min-height: 260px;
}

.path-card a,
.link-card:hover h3 {
  color: var(--teal);
  font-weight: 900;
}

.chapter-sections {
  display: grid;
  gap: 10px;
  margin: 20px 0 0;
  padding: 0;
  list-style: none;
}

.chapter-sections li {
  padding: 9px 0 9px 14px;
  border-left: 3px solid rgba(15, 118, 110, 0.28);
  color: var(--ink);
  font-size: 16px;
  font-weight: 850;
  line-height: 1.45;
}

.step-number,
.module-icon {
  display: inline-grid;
  width: 48px;
  height: 48px;
  margin-bottom: 22px;
  place-items: center;
  border-radius: 12px;
  color: #fff;
  background: var(--blue);
  font-weight: 900;
}

.path-card:nth-child(2) .step-number,
.module-card:nth-child(2) .module-icon {
  background: var(--teal);
}

.path-card:nth-child(3) .step-number,
.module-card:nth-child(3) .module-icon {
  background: var(--amber);
}

.module-card:nth-child(4) .module-icon {
  background: var(--rose);
}

.module-card:nth-child(5) .module-icon {
  background: var(--violet);
}

.link-card {
  display: block;
  min-height: 230px;
}

.practice-layout {
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(320px, 0.95fr);
  gap: 18px;
  margin-top: 30px;
}

.answers {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 12px;
  margin-top: 22px;
}

.answers button {
  min-height: 68px;
  padding: 12px 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  color: var(--ink);
  background: #fff;
  text-align: left;
}

.answers button:hover,
.answers button:focus-visible {
  border-color: var(--teal);
}

.answers button.is-correct {
  border-color: var(--teal);
  background: #e4f6f2;
}

.answers button.is-wrong {
  border-color: var(--rose);
  background: #fff0f3;
}

.quiz-result {
  min-height: 28px;
  margin: 18px 0 0;
  font-weight: 850;
}

.checklist {
  display: grid;
  gap: 12px;
  margin-top: 18px;
}

.checklist label {
  display: flex;
  align-items: center;
  gap: 10px;
  min-height: 44px;
  padding: 10px 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--paper-soft);
}

.checklist input {
  width: 18px;
  height: 18px;
  accent-color: var(--teal);
}

.page-hero {
  padding: clamp(56px, 8vw, 104px) clamp(18px, 5vw, 76px) clamp(34px, 5vw, 56px);
  background:
    linear-gradient(90deg, rgba(255, 255, 255, 0.92), rgba(255, 255, 255, 0.62)),
    url("../assets/chemistry-hero.svg") right center / min(54vw, 720px) auto no-repeat;
}

.page-hero h1 {
  max-width: 820px;
}

.page-hero p {
  max-width: 680px;
  font-size: 19px;
}

.filter-bar {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 24px;
}

.filter-chip {
  min-height: 40px;
  padding: 0 14px;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--muted);
  background: var(--paper);
  font-weight: 850;
}

.filter-chip.active {
  color: #fff;
  border-color: var(--teal);
  background: var(--teal);
}

.knowledge-card {
  min-height: 310px;
}

.knowledge-card span,
.exam-card span,
.equation-item span {
  display: block;
  margin-bottom: 12px;
  color: var(--teal);
  font-size: 13px;
  font-weight: 900;
}

.knowledge-card ul,
.exam-card ul {
  margin: 18px 0 0;
  padding-left: 20px;
  color: var(--muted);
}

.knowledge-card.is-hidden {
  display: none;
}

.highlight-card {
  border-color: rgba(15, 118, 110, 0.32);
  background: linear-gradient(180deg, #ffffff, #eef8f5);
}

.text-link {
  display: inline-flex;
  margin-top: 10px;
  color: var(--teal);
  font-weight: 900;
}

.search-label {
  display: block;
  margin: 26px 0 8px;
  font-weight: 900;
}

.search-input {
  width: min(100%, 460px);
  height: 50px;
  padding: 0 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  outline: 0;
  background: #fff;
}

.wide-input {
  width: min(100%, 680px);
}

.search-input:focus {
  border-color: var(--teal);
  box-shadow: 0 0 0 4px rgba(15, 118, 110, 0.12);
}

.equation-board {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 14px;
}

.equation-item {
  padding: 22px;
}

.equation-item strong {
  display: block;
  margin-bottom: 12px;
  overflow-wrap: anywhere;
  font-size: clamp(20px, 2.5vw, 30px);
  line-height: 1.25;
}

.equation-item.is-hidden {
  display: none;
}

.lab-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: 18px;
}

.safety-grid {
  display: grid;
  gap: 12px;
  margin-top: 20px;
}

.safety-grid article {
  padding: 18px;
}

.safety-grid strong,
.timeline strong {
  display: block;
  margin-bottom: 6px;
  font-size: 20px;
}

.timeline {
  display: grid;
  gap: 16px;
  margin-top: 20px;
}

.timeline div {
  position: relative;
  padding-left: 28px;
}

.timeline div::before {
  position: absolute;
  left: 0;
  top: 8px;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--amber);
  content: "";
}

.exam-grid {
  grid-template-columns: repeat(2, 1fr);
}

.exam-card {
  min-height: 300px;
}

.muted-copy {
  max-width: 760px;
  color: var(--muted);
}

.compulsory-hero {
  position: relative;
  display: grid;
  grid-template-columns: minmax(0, 0.72fr) minmax(320px, 0.48fr);
  gap: clamp(22px, 4vw, 54px);
  align-items: center;
  min-height: 680px;
  padding-top: clamp(74px, 10vw, 132px);
  padding-bottom: clamp(54px, 8vw, 96px);
  overflow: hidden;
  background:
    linear-gradient(90deg, rgba(247, 253, 250, 0.99) 0%, rgba(247, 253, 250, 0.94) 30%, rgba(247, 253, 250, 0.64) 52%, rgba(247, 253, 250, 0.1) 82%),
    linear-gradient(180deg, rgba(247, 253, 250, 0.05), rgba(247, 253, 250, 0.28)),
    url("../assets/compulsory1-opening-lab.jpg") center center / cover no-repeat,
    linear-gradient(135deg, #f7fffc 0%, #edf7f4 54%, #f8f5ec 100%);
  box-shadow: inset 0 -1px 0 rgba(15, 118, 110, 0.12);
}

.compulsory-hero::before {
  position: absolute;
  inset: 0;
  background:
    linear-gradient(90deg, rgba(15, 118, 110, 0.055) 1px, transparent 1px),
    linear-gradient(180deg, rgba(19, 35, 33, 0.04) 1px, transparent 1px);
  background-size: 64px 64px;
  -webkit-mask-image: linear-gradient(90deg, transparent 0%, rgba(0, 0, 0, 0.18) 48%, rgba(0, 0, 0, 0.7) 100%);
  mask-image: linear-gradient(90deg, transparent 0%, rgba(0, 0, 0, 0.18) 48%, rgba(0, 0, 0, 0.7) 100%);
  pointer-events: none;
  content: "";
}

.compulsory-hero::after {
  position: absolute;
  right: clamp(18px, 5vw, 76px);
  bottom: 18px;
  left: clamp(18px, 5vw, 76px);
  height: 1px;
  background: linear-gradient(90deg, transparent, rgba(15, 118, 110, 0.22), transparent);
  content: "";
}

.compulsory-hero-copy {
  position: relative;
  z-index: 2;
  max-width: 820px;
}

.compulsory-hero-copy h1 {
  max-width: 760px;
  margin-bottom: 18px;
  font-size: clamp(58px, 7.2vw, 108px);
  line-height: 0.98;
}

.hero-subtitle {
  max-width: 680px;
  margin-bottom: 18px;
  color: var(--teal);
  font-size: clamp(28px, 3.2vw, 44px);
  font-weight: 900;
  line-height: 1.18;
}

.hero-importance {
  max-width: 720px;
  color: var(--muted);
  font-size: clamp(17px, 1.6vw, 22px);
  font-weight: 750;
}

.compulsory-hero .primary-action {
  background: linear-gradient(135deg, #0f766e, #2678d7);
  box-shadow: 0 18px 34px rgba(15, 118, 110, 0.24);
}

.compulsory-hero .secondary-action {
  border-color: rgba(15, 118, 110, 0.18);
  background: rgba(255, 255, 255, 0.82);
  box-shadow: 0 12px 28px rgba(26, 53, 49, 0.07);
  backdrop-filter: blur(10px);
}

.floating-toolbox {
  --toolbox-panel-gap: 340px;
  position: fixed;
  top: 38vh;
  right: 28px;
  z-index: 80;
  touch-action: none;
}

.toolbox-toggle {
  position: relative;
  z-index: 3;
  display: grid;
  width: 58px;
  height: 58px;
  place-items: center;
  border: 1px solid rgba(15, 118, 110, 0.24);
  border-radius: 50%;
  color: #fff;
  background: linear-gradient(135deg, var(--teal), var(--blue));
  box-shadow: 0 18px 42px rgba(15, 118, 110, 0.28);
  cursor: grab;
}

.toolbox-toggle:active {
  cursor: grabbing;
}

.toolbox-toggle svg {
  width: 27px;
  height: 27px;
  fill: none;
  stroke: currentColor;
  stroke-width: 2.2;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.toolbox-fan {
  position: absolute;
  inset: 0;
  z-index: 2;
  pointer-events: none;
}

.fan-item {
  position: absolute;
  left: 50%;
  top: 50%;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 96px;
  min-height: 38px;
  padding: 0 12px;
  border: 1px solid rgba(15, 118, 110, 0.22);
  border-radius: 999px;
  color: var(--ink);
  background: rgba(255, 255, 255, 0.96);
  box-shadow: 0 14px 30px rgba(26, 53, 49, 0.12);
  opacity: 0;
  pointer-events: none;
  transform: translate(-50%, -50%) scale(0.62);
  transition:
    opacity 180ms ease,
    transform 260ms cubic-bezier(0.2, 0.86, 0.24, 1.12),
    color 160ms ease,
    background 160ms ease,
    border-color 160ms ease;
  white-space: nowrap;
}

.fan-item span {
  font-size: 13px;
  font-weight: 900;
  line-height: 1;
}

.floating-toolbox.is-open .fan-item {
  opacity: 1;
  pointer-events: auto;
  transform: translate(calc(-50% + var(--fan-x)), calc(-50% + var(--fan-y))) scale(1);
}

.floating-toolbox.opens-right.is-open .fan-item {
  transform: translate(calc(-50% - var(--fan-x)), calc(-50% + var(--fan-y))) scale(1);
}

.fan-item:hover,
.fan-item.active {
  border-color: rgba(15, 118, 110, 0.44);
  color: #fff;
  background: linear-gradient(135deg, var(--teal), var(--blue));
}

.floating-tool-panel {
  position: absolute;
  top: 0;
  right: var(--toolbox-panel-gap);
  display: grid;
  gap: 10px;
  width: min(360px, calc(100vw - 104px));
  max-height: min(520px, calc(100vh - 36px));
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.96), rgba(238, 248, 245, 0.92));
  box-shadow: var(--soft-shadow);
  overflow-y: auto;
  opacity: 0;
  pointer-events: none;
  transform: translateX(10px);
  transition: opacity 180ms ease 80ms, transform 220ms ease 80ms;
}

.floating-toolbox.has-active-tool .floating-tool-panel {
  opacity: 1;
  pointer-events: auto;
  transform: translateX(0);
}

.floating-toolbox.has-active-tool .tool-pane.active {
  animation: toolPaneIn 220ms ease both;
}

.floating-toolbox.opens-right .floating-tool-panel {
  right: auto;
  left: var(--toolbox-panel-gap);
  transform: translateX(-10px);
}

.floating-toolbox.opens-right.has-active-tool .floating-tool-panel {
  transform: translateX(0);
}

.floating-toolbox.is-periodic-modal-open .floating-tool-panel {
  position: fixed;
  inset: 0;
  z-index: 120;
  display: grid;
  place-items: center;
  width: auto;
  max-height: none;
  padding: clamp(18px, 3vw, 42px);
  border: 0;
  border-radius: 0;
  background: rgba(6, 18, 22, 0.72);
  box-shadow: none;
  opacity: 1;
  pointer-events: auto;
  transform: none;
  backdrop-filter: blur(5px);
}

.floating-toolbox.is-periodic-modal-open .tool-column-head,
.floating-toolbox.is-periodic-modal-open .tool-pane:not(.periodic-pane) {
  display: none;
}

.tool-pane {
  display: none;
  min-width: 0;
}

.tool-pane.active {
  display: block;
}

.placeholder-pane p {
  margin: 0;
  color: var(--muted);
  font-weight: 750;
}

.periodic-pane {
  padding: 14px;
  min-width: 0;
}

.floating-toolbox.is-periodic-modal-open .periodic-pane {
  display: flex;
  flex-direction: column;
  width: min(1480px, calc(100vw - 56px));
  height: calc(100vh - 56px);
  max-height: 900px;
  padding: 22px;
  border: 1px solid rgba(217, 230, 226, 0.94);
  border-radius: 8px;
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.99), rgba(239, 248, 245, 0.98));
  box-shadow: 0 34px 90px rgba(0, 0, 0, 0.34);
  overflow: hidden;
  animation: periodicPaneIn 240ms cubic-bezier(0.2, 0.82, 0.22, 1) both;
}

.periodic-close {
  min-height: 34px;
  padding: 0 12px;
  border: 1px solid rgba(15, 118, 110, 0.22);
  border-radius: 999px;
  color: var(--teal);
  background: #fff;
  font-size: 13px;
  font-weight: 900;
}

.periodic-embed-wrap {
  flex: 1;
  min-width: 0;
  min-height: 0;
  margin-top: 12px;
  overflow: auto;
  border: 1px solid rgba(128, 234, 255, 0.2);
  border-radius: 6px;
  background: #101318;
  box-shadow: inset 0 0 0 1px rgba(255, 255, 255, 0.025);
  overscroll-behavior: contain;
}

.periodic-embed {
  display: block;
  width: 100%;
  min-width: 980px;
  height: 100%;
  min-height: 620px;
  border: 0;
  background: #101318;
}

.periodic-table-wrap {
  margin-top: 12px;
  overflow: auto;
  min-width: 0;
  border: 1px solid var(--line);
  border-radius: 8px;
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.98), rgba(244, 249, 247, 0.98));
}

.periodic-table {
  display: grid;
  grid-template-columns: 48px repeat(18, 68px);
  grid-template-rows: 42px repeat(9, 82px);
  gap: 4px;
  min-width: 1360px;
  padding: 12px;
}

.periodic-table .element {
  transition: border-color 160ms ease, box-shadow 160ms ease, transform 160ms ease;
}

.periodic-table .element:hover {
  border-color: rgba(15, 118, 110, 0.42);
  box-shadow: 0 12px 22px rgba(26, 53, 49, 0.13);
  transform: translateY(-2px);
}

.element,
.series-label {
  grid-column: var(--pc, var(--c));
  grid-row: calc(var(--r) + 1);
}

.group-label {
  display: grid;
  grid-column: var(--c) / span var(--span);
  grid-row: 1;
  place-items: center;
  gap: 2px;
  min-width: 0;
  border: 1px solid rgba(15, 118, 110, 0.18);
  border-radius: 6px;
  color: var(--teal);
  background: rgba(255, 255, 255, 0.92);
  line-height: 1;
}

.group-label strong {
  color: inherit;
  font-size: 12px;
  font-weight: 950;
  letter-spacing: 0;
  white-space: nowrap;
}

.group-label span {
  color: rgba(19, 35, 33, 0.64);
  font-size: 10px;
  font-weight: 900;
  line-height: 1;
}

.group-label.sub {
  color: #2678d7;
  background: rgba(233, 242, 255, 0.96);
}

.group-label.main {
  background: rgba(238, 248, 245, 0.96);
}

.period-label {
  display: grid;
  grid-column: 1;
  grid-row: calc(var(--r) + 1);
  place-items: center;
  min-width: 0;
  padding: 4px;
  border: 1px solid rgba(15, 118, 110, 0.16);
  border-radius: 6px;
  color: var(--teal);
  background: rgba(238, 248, 245, 0.92);
  font-size: 11px;
  font-weight: 950;
  line-height: 1.15;
  text-align: center;
  writing-mode: vertical-rl;
  letter-spacing: 0;
}

.element {
  position: relative;
  display: grid;
  grid-template-rows: 14px 27px 16px 14px;
  align-content: center;
  row-gap: 2px;
  min-width: 0;
  padding: 6px 8px;
  border: 1px solid rgba(15, 118, 110, 0.16);
  border-radius: 6px;
  background: #fff;
  box-shadow: 0 6px 14px rgba(26, 53, 49, 0.06);
}

.element small {
  grid-row: 1;
  color: var(--muted);
  font-size: 11px;
  font-weight: 850;
  line-height: 1.05;
}

.element b {
  grid-row: 2;
  min-width: 0;
  overflow: hidden;
  color: var(--ink);
  font-size: 21px;
  line-height: 1.02;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.element span {
  grid-row: 3;
  min-width: 0;
  overflow: hidden;
  color: var(--muted);
  font-size: 12px;
  font-weight: 850;
  line-height: 1.05;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.element em {
  grid-row: 4;
  min-width: 0;
  overflow: hidden;
  color: rgba(19, 35, 33, 0.72);
  font-size: 10px;
  font-style: normal;
  font-weight: 850;
  line-height: 1.05;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.series-label {
  display: grid;
  place-items: center;
  border: 1px dashed rgba(15, 118, 110, 0.28);
  border-radius: 6px;
  color: var(--teal);
  background: rgba(238, 248, 245, 0.78);
  font-size: 13px;
  font-weight: 900;
}

.element.alkali,
.periodic-legend .alkali {
  background: #fff4dd;
}

.element.alkaline,
.periodic-legend .alkaline {
  background: #eaf7ef;
}

.element.transition,
.periodic-legend .transition {
  background: #e9f2ff;
}

.element.post,
.element.metalloid {
  background: #f3eefb;
}

.element.nonmetal,
.periodic-legend .nonmetal {
  background: #eef8f5;
}

.element.halogen,
.periodic-legend .halogen {
  background: #fff0f3;
}

.element.noble,
.periodic-legend .noble {
  background: #edf1ff;
}

.element.lanth,
.element.act {
  background: #f8f5ec;
}

.periodic-legend {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 10px;
}

.periodic-legend span {
  display: inline-flex;
  align-items: center;
  min-height: 28px;
  padding: 0 10px;
  border: 1px solid rgba(15, 118, 110, 0.14);
  border-radius: 999px;
  color: var(--ink);
  font-size: 12px;
  font-weight: 850;
}

.tool-column-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--line);
}

.tool-column-head span,
.mini-title span {
  color: var(--teal);
  font-size: 13px;
  font-weight: 900;
}

.tool-column-head strong {
  font-size: 22px;
  line-height: 1.15;
}

.tool-mini {
  padding: 12px;
  border: 1px solid rgba(217, 230, 226, 0.92);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.86);
}

.mini-title {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 10px;
}

.mini-title strong {
  font-size: 17px;
  line-height: 1.2;
}

.mini-checklist {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 6px;
  margin-top: 10px;
}

.mini-checklist label {
  display: flex;
  align-items: center;
  gap: 6px;
  min-height: 32px;
  padding: 6px 8px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  font-size: 13px;
  font-weight: 850;
}

.mini-checklist input {
  width: 16px;
  height: 16px;
  accent-color: var(--teal);
}

.tool-form {
  display: grid;
  gap: 12px;
}

.mini-tool-form {
  grid-template-columns: repeat(2, 1fr);
  gap: 8px;
}

.tool-form label {
  display: grid;
  gap: 6px;
  color: var(--muted);
  font-size: 13px;
  font-weight: 850;
}

.tool-form input {
  width: 100%;
  min-height: 40px;
  padding: 0 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  color: var(--ink);
  background: #fff;
  font-weight: 850;
}

.tool-result {
  margin-top: 18px;
  padding: 18px;
  border: 1px solid rgba(15, 118, 110, 0.18);
  border-radius: 8px;
  background: linear-gradient(180deg, #ffffff, #eef8f5);
}

.mini-result {
  margin-top: 10px;
  padding: 12px;
}

.tool-result small {
  display: block;
  margin-bottom: 8px;
  color: var(--muted);
  font-weight: 850;
}

.tool-result strong {
  display: block;
  font-size: clamp(18px, 1.6vw, 24px);
  line-height: 1.18;
}

.tool-result p {
  margin: 10px 0 0;
  color: var(--muted);
}

.ion-options {
  display: grid;
  gap: 10px;
}

.mini-ion-options {
  grid-template-columns: 1fr;
  gap: 8px;
}

.ion-options button {
  min-height: 44px;
  padding: 0 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  color: var(--ink);
  background: #fff;
  font-weight: 900;
  text-align: left;
}

.ion-options button.active,
.ion-options button:hover {
  border-color: rgba(15, 118, 110, 0.34);
  color: var(--teal);
  background: #eef8f5;
}

.arithmetic-mini {
  display: grid;
  gap: 12px;
}

.calc-display {
  display: grid;
  gap: 6px;
}

.calc-display input {
  width: 100%;
  min-height: 54px;
  padding: 0 14px;
  border: 1px solid rgba(15, 118, 110, 0.24);
  border-radius: 8px;
  color: var(--ink);
  background: linear-gradient(180deg, #ffffff, #f3fbf8);
  font-size: 24px;
  font-weight: 900;
  font-variant-numeric: tabular-nums;
  text-align: right;
}

.calc-display small {
  color: var(--muted);
  font-size: 12px;
  font-weight: 850;
}

.calc-display small.is-error {
  color: #b42318;
}

.calc-keypad {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 8px;
}

.calc-keypad button {
  min-width: 0;
  min-height: 42px;
  border: 1px solid var(--line);
  border-radius: 8px;
  color: var(--ink);
  background: #fff;
  font-size: 15px;
  font-weight: 900;
  cursor: pointer;
}

.calc-keypad button:hover {
  border-color: rgba(15, 118, 110, 0.36);
  background: #f1fbf7;
}

.calc-keypad .operator {
  color: #0f766e;
  background: #edf8f5;
}

.calc-keypad .equals {
  color: #fff;
  border-color: #0f766e;
  background: #0f766e;
}

.syllabus-grid {
  grid-template-columns: repeat(4, 1fr);
}

.syllabus-grid article {
  position: relative;
  min-height: 230px;
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.98), rgba(247, 252, 250, 0.98));
}

.syllabus-grid article::after {
  position: absolute;
  right: 22px;
  bottom: 20px;
  left: 22px;
  height: 1px;
  background: linear-gradient(90deg, rgba(15, 118, 110, 0.26), transparent);
  content: "";
}

.syllabus-grid span {
  display: block;
  margin-bottom: 12px;
  color: var(--teal);
  font-size: 13px;
  font-weight: 900;
}

.question-bank {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 16px;
  margin-top: 26px;
}

.question-card {
  min-height: 300px;
}

.question-card span {
  display: block;
  margin-bottom: 10px;
  color: var(--teal);
  font-size: 13px;
  font-weight: 900;
}

.answer-toggle {
  min-height: 40px;
  margin-top: 12px;
  padding: 0 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  color: var(--teal);
  background: #fff;
  font-weight: 900;
}

.answer-panel {
  display: none;
  margin-top: 14px;
  padding: 16px;
  border: 1px solid rgba(15, 118, 110, 0.22);
  border-radius: 8px;
  background: #eef8f5;
}

.answer-panel.is-open {
  display: block;
}

.answer-panel strong {
  display: block;
  margin-bottom: 8px;
}

.question-card.is-hidden {
  display: none;
}

.drill-section {
  background: linear-gradient(180deg, #fbfdfc, #eef7f5);
}

.drill-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 16px;
  margin-top: 26px;
}

.drill-card {
  padding: 24px;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: var(--paper);
  box-shadow: var(--soft-shadow);
}

.drill-card > span {
  display: block;
  margin-bottom: 10px;
  color: var(--teal);
  font-size: 13px;
  font-weight: 900;
}

.drill-card ol {
  margin: 16px 0 0;
  padding-left: 22px;
  color: var(--muted);
}

.drill-card li + li {
  margin-top: 8px;
}

.drill-card.is-hidden {
  display: none;
}

.tree-section {
  background: linear-gradient(180deg, #fbfdfc, #eef7f5);
}

.dispersion-section {
  min-width: 0;
  background: transparent;
}

.dispersion-knowledge {
  overflow: visible;
}

.dispersion-section .knowledge-point:first-child {
  padding-top: 0;
}

.dispersion-section .knowledge-point:last-child {
  padding-bottom: 0;
}

.point-body > .dispersion-figure,
.point-body .dispersion-table-wrap,
.point-body .dispersion-property-grid {
  margin-top: 16px;
}

.point-body > .dispersion-trap-list {
  grid-template-columns: minmax(0, 1fr);
  gap: 14px;
  margin-top: 14px;
  padding: 20px 22px;
}

.dispersion-table-head h3,
.dispersion-detail h3,
.dispersion-properties-head h3,
.dispersion-trap-list h3 {
  margin: 0;
}

.dispersion-table-head > p,
.dispersion-properties-head > p {
  max-width: 700px;
  margin: 12px 0 0;
  color: var(--muted);
  font-size: 17px;
  font-weight: 680;
}

.dispersion-intro-grid,
.dispersion-detail-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: clamp(24px, 4vw, 54px);
  align-items: center;
  margin-top: clamp(30px, 4vw, 52px);
}

.point-body .dispersion-intro-grid {
  grid-template-columns: minmax(0, 1fr);
  margin-top: 14px;
  gap: 18px;
}

.dispersion-definition h3 {
  margin: 0 0 18px;
  font-size: clamp(24px, 3vw, 34px);
  line-height: 1.28;
}

.dispersion-definition-list {
  display: grid;
  gap: 12px;
  margin: 0;
}

.dispersion-definition-list div {
  display: grid;
  grid-template-columns: 104px minmax(0, 1fr);
  gap: 14px;
  align-items: start;
  padding: 14px 0;
  border-bottom: 1px solid var(--line);
}

.dispersion-definition-list dt {
  color: var(--ink);
  font-weight: 950;
}

.dispersion-definition-list dd {
  margin: 0;
  color: var(--muted);
}

.dispersion-note,
.dispersion-caution {
  margin: 18px 0 0;
  padding: 13px 15px;
  border-left: 3px solid var(--amber);
  color: #5b5142;
  background: rgba(255, 248, 234, 0.82);
  font-size: 15px;
  line-height: 1.74;
}

.dispersion-note strong,
.dispersion-caution strong {
  color: #9a5c0e;
}

.dispersion-figure {
  margin: 0;
  padding: clamp(12px, 1.8vw, 18px);
  border: 1px solid var(--line);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.94);
  box-shadow: 0 14px 34px rgba(26, 53, 49, 0.08);
}

.dispersion-figure img {
  display: block;
  width: 100%;
  height: auto;
  object-fit: contain;
}

.dispersion-scale-figure {
  width: min(100%, 760px);
  padding: 10px 12px;
  justify-self: center;
}

.dispersion-scale-figure img {
  max-height: none;
}

.dispersion-figure figcaption {
  margin-top: 10px;
  color: var(--muted);
  font-size: 13px;
  font-weight: 850;
  text-align: center;
}

.dispersion-table-head,
.dispersion-properties-head {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 24px;
  margin-top: clamp(46px, 6vw, 78px);
}

.dispersion-table-head h3,
.dispersion-properties-head h3 {
  font-size: clamp(24px, 3vw, 34px);
  line-height: 1.22;
}

.dispersion-table-head > p,
.dispersion-properties-head > p {
  max-width: 430px;
  margin: 0;
  font-size: 15px;
  text-align: right;
}

.dispersion-table-wrap {
  margin-top: 18px;
  overflow-x: auto;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  box-shadow: 0 16px 36px rgba(26, 53, 49, 0.08);
}

.dispersion-table {
  width: 100%;
  min-width: 930px;
  border-spacing: 0;
  border-collapse: separate;
  color: var(--ink);
  table-layout: fixed;
}

.dispersion-table th,
.dispersion-table td {
  padding: 15px 16px;
  border-right: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  vertical-align: middle;
  font-size: 15px;
  line-height: 1.58;
  text-align: center;
}

.dispersion-table thead th {
  color: var(--ink);
  font-size: 16px;
  font-weight: 950;
}

.dispersion-table thead tr:first-child th {
  border-bottom-color: rgba(255, 255, 255, 0.62);
}

.dispersion-table thead th:first-child {
  width: 16%;
  color: #41605a;
  background: #eff5f3;
}

.dispersion-table .solution-column {
  width: 19%;
  color: #215a9c;
  background: #eaf2fd;
}

.dispersion-table .colloid-column {
  width: 22%;
  color: #087066;
  background: #e3f4ef;
}

.dispersion-table .turbid-column {
  color: #974850;
  background: #fbecef;
}

.dispersion-table .suspension-column,
.dispersion-table .emulsion-column {
  width: 21.5%;
  color: #974850;
  background: #fff5f2;
}

.dispersion-table tbody th {
  color: #41605a;
  background: #f8fbfa;
  font-weight: 900;
  text-align: left;
}

.dispersion-table tbody td:nth-child(2) {
  background: rgba(234, 242, 253, 0.43);
}

.dispersion-table tbody td:nth-child(3) {
  background: rgba(227, 244, 239, 0.48);
}

.dispersion-table tbody td:nth-child(4),
.dispersion-table tbody td:nth-child(5) {
  background: rgba(255, 245, 242, 0.58);
}

.dispersion-table tr:last-child > * {
  border-bottom: 0;
}

.dispersion-table tr > *:last-child {
  border-right: 0;
}

.dispersion-table strong {
  color: inherit;
  font-size: 17px;
}

.comparison-state {
  display: inline-flex;
  justify-content: center;
  min-width: 4.4em;
  padding: 3px 10px;
  border-radius: 999px;
  font-size: 13px;
  font-weight: 950;
}

.stable-state {
  color: #1d5d9e;
  background: #dcecff;
}

.medium-state {
  color: #087066;
  background: #d8f0e8;
}

.unstable-state {
  color: #a24750;
  background: #fbe2e5;
}

.dispersion-detail-grid {
  align-items: start;
}

.dispersion-detail {
  min-width: 0;
}

.dispersion-detail .dispersion-figure {
  margin-top: 16px;
}

.dispersion-detail .dispersion-figure img {
  max-height: 280px;
}

.dispersion-type-list {
  display: grid;
  gap: 0;
  margin: 16px 0 0;
  padding: 0;
  list-style: none;
  border-top: 1px solid var(--line);
}

.dispersion-type-list li {
  display: grid;
  grid-template-columns: 80px minmax(0, 1fr);
  gap: 12px;
  padding: 12px 0;
  border-bottom: 1px solid var(--line);
}

.dispersion-type-list strong {
  color: var(--teal);
  font-size: 15px;
}

.dispersion-type-list span,
.dispersion-steps {
  color: var(--muted);
  font-size: 15px;
}

.dispersion-steps {
  display: grid;
  gap: 8px;
  margin: 18px 0 0;
  padding-left: 22px;
}

.dispersion-steps li {
  padding-left: 4px;
}

.dispersion-equation {
  margin: 18px 0 0;
  padding: 13px 14px;
  border: 1px solid rgba(15, 118, 110, 0.18);
  color: #175d56;
  background: rgba(234, 248, 244, 0.74);
  font-family: "Times New Roman", "Songti SC", serif;
  font-size: 17px;
  font-weight: 700;
  text-align: center;
}

.dispersion-equation span {
  display: inline-block;
  margin: 0 3px;
  color: var(--teal);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  font-size: 11px;
  font-weight: 900;
  vertical-align: 9px;
}

.dispersion-property-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 14px;
  margin-top: 18px;
}

.dispersion-property {
  min-width: 0;
  padding: 18px;
  border-top: 3px solid var(--teal);
  background: rgba(255, 255, 255, 0.88);
}

.dispersion-property h4 {
  margin: 0 0 14px;
  font-size: 19px;
  line-height: 1.25;
}

.dispersion-property p {
  margin: 0 0 10px;
  color: var(--muted);
  font-size: 14px;
  line-height: 1.72;
}

.dispersion-property p:last-child {
  margin-bottom: 0;
}

.dispersion-property strong {
  color: var(--ink);
}

.property-tyndall {
  border-top-color: var(--amber);
  background: #fffaf0;
}

.property-coagulation {
  border-top-color: var(--rose);
  background: #fff7f8;
}

.property-dialysis {
  border-top-color: var(--blue);
  background: #f4f8ff;
}

.property-electrophoresis {
  border-top-color: var(--violet);
  background: #f8f6ff;
}

.dispersion-trap-list {
  display: grid;
  grid-template-columns: minmax(240px, 0.54fr) minmax(0, 1.46fr);
  gap: clamp(24px, 4vw, 58px);
  align-items: start;
  margin-top: clamp(40px, 5vw, 64px);
  padding: clamp(24px, 3vw, 34px);
  border-left: 4px solid var(--rose);
  background: #fff6f7;
}

.dispersion-trap-list ul {
  display: grid;
  gap: 10px;
  margin: 0;
  padding-left: 22px;
  color: #665b5d;
}

.dispersion-trap-list li {
  padding-left: 4px;
}

.tree-viewer {
  margin-top: 28px;
  overflow-x: auto;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: #f4f8f9;
  box-shadow: var(--shadow);
}

.tree-viewer img {
  display: block;
  width: 100%;
  min-width: 920px;
  height: auto;
}

.tree-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
  margin-top: 18px;
}

.mindmap-divider {
  height: 1px;
  margin: clamp(42px, 6vw, 72px) 0 clamp(30px, 4vw, 46px);
  background: linear-gradient(90deg, transparent, rgba(15, 118, 110, 0.34), transparent);
}

.map-subhead {
  margin-bottom: 0;
}

.notes-section {
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.96), rgba(238, 246, 243, 0.82)),
    repeating-linear-gradient(90deg, transparent 0 56px, rgba(15, 118, 110, 0.035) 56px 57px);
}

.notes-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 18px;
  margin-top: 30px;
}

.note-card {
  padding: 26px;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: var(--paper);
  box-shadow: var(--soft-shadow);
}

.note-card > span {
  display: block;
  margin-bottom: 10px;
  color: var(--teal);
  font-size: 13px;
  font-weight: 900;
}

.note-item {
  padding: 16px 0;
  border-top: 1px solid var(--line);
}

.note-item:first-of-type {
  margin-top: 8px;
}

.note-item strong {
  display: block;
  margin-bottom: 6px;
  font-size: 17px;
}

.note-item p {
  margin-bottom: 0;
  color: var(--muted);
}

.framework-list {
  display: grid;
  gap: 22px;
  margin-top: 30px;
}

.chapter-frame {
  position: relative;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--paper);
  box-shadow: var(--soft-shadow);
  overflow: hidden;
}

.chapter-frame::before {
  position: absolute;
  inset: 0 0 auto;
  height: 2px;
  background: linear-gradient(90deg, var(--teal), var(--blue), var(--amber));
  content: "";
}

.chapter-title {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  padding: 24px 26px;
  border-bottom: 1px solid var(--line);
  background: linear-gradient(90deg, rgba(15, 118, 110, 0.1), rgba(59, 116, 215, 0.08));
}

.chapter-title span {
  color: var(--teal);
  font-size: 13px;
  font-weight: 900;
}

.chapter-title h3 {
  margin-bottom: 0;
  text-align: right;
}

.lesson-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1px;
  background: var(--line);
}

.lesson-card {
  position: relative;
  min-height: 260px;
  padding: 22px;
  background: var(--paper);
  transition: background 160ms ease, box-shadow 160ms ease;
}

.lesson-card::after {
  position: absolute;
  right: 22px;
  bottom: 18px;
  left: 22px;
  height: 1px;
  background: linear-gradient(90deg, rgba(15, 118, 110, 0.2), transparent);
  opacity: 0;
  transition: opacity 160ms ease;
  content: "";
}

.lesson-card:hover {
  background: linear-gradient(180deg, #fff, #f7fcfa);
}

.lesson-card:hover::after {
  opacity: 1;
}

.lesson-card span {
  display: block;
  margin-bottom: 10px;
  color: var(--teal);
  font-size: 13px;
  font-weight: 900;
}

.lesson-card h4 {
  margin: 0 0 10px;
  font-size: 20px;
  line-height: 1.25;
}

.classification-board {
  display: block;
  background: var(--paper);
}

.classification-knowledge,
.classification-visuals {
  min-width: 0;
  background: var(--paper);
}

.classification-knowledge {
  padding: clamp(22px, 3vw, 34px);
}

.lesson-note-heading {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 6px;
  padding-bottom: 18px;
  border-bottom: 2px solid rgba(15, 118, 110, 0.18);
}

.lesson-note-heading span {
  color: var(--teal);
  font-size: 13px;
  font-weight: 900;
}

.classification-knowledge h4 {
  margin: 0;
  font-size: clamp(24px, 2.8vw, 34px);
  line-height: 1.18;
}

.classification-knowledge > p {
  margin-bottom: 16px;
  color: var(--muted);
  font-size: 17px;
  font-weight: 760;
}

.knowledge-block {
  padding: 15px 0;
  border-top: 1px solid var(--line);
}

.knowledge-block:first-of-type {
  margin-top: 18px;
}

.knowledge-block strong {
  display: block;
  margin-bottom: 6px;
  color: var(--ink);
  font-size: 17px;
}

.knowledge-block p {
  margin-bottom: 0;
  color: var(--muted);
  overflow-wrap: anywhere;
}

.classification-knowledge > p {
  overflow-wrap: anywhere;
}

.knowledge-point {
  display: grid;
  grid-template-columns: 52px minmax(0, 1fr);
  gap: 18px;
  padding: 22px 0;
  border-bottom: 1px solid var(--line);
}

.knowledge-point:last-child {
  border-bottom: 0;
}

.point-number {
  display: inline-grid;
  width: 40px;
  height: 40px;
  place-items: center;
  border: 1px solid rgba(15, 118, 110, 0.18);
  border-radius: 8px;
  color: var(--teal);
  background: rgba(238, 248, 245, 0.9);
  font-size: 14px;
  font-weight: 950;
}

.point-body {
  min-width: 0;
}

.point-body h5 {
  margin: 0 0 10px;
  color: var(--ink);
  font-size: clamp(19px, 2vw, 24px);
  line-height: 1.22;
}

.point-body p {
  margin-bottom: 8px;
  color: var(--muted);
  font-size: 16px;
  line-height: 1.78;
  overflow-wrap: anywhere;
}

.point-body p:last-child {
  margin-bottom: 0;
}

.point-body em {
  display: inline-flex;
  align-items: center;
  min-height: 26px;
  margin-right: 8px;
  padding: 0 9px;
  border-radius: 999px;
  color: var(--teal);
  background: rgba(15, 118, 110, 0.1);
  font-size: 13px;
  font-style: normal;
  font-weight: 900;
  vertical-align: 1px;
}

.taxonomy-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 14px;
  margin: 16px 0 12px;
}

.taxonomy-card {
  min-width: 0;
  padding: 16px;
  border: 1px solid rgba(217, 230, 226, 0.94);
  border-radius: 8px;
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.98), rgba(248, 251, 250, 0.98)),
    repeating-linear-gradient(0deg, transparent 0 31px, rgba(15, 118, 110, 0.045) 31px 32px);
}

.taxonomy-card h6 {
  margin: 0 0 10px;
  color: var(--ink);
  font-size: 17px;
  font-weight: 950;
}

.taxonomy-card p {
  margin: 0 0 8px;
  color: var(--muted);
  font-size: 14px;
  line-height: 1.68;
}

.taxonomy-card p:last-child {
  margin-bottom: 0;
}

.taxonomy-card-wide {
  grid-column: span 2;
}

.taxonomy-card strong {
  display: inline-block;
  min-width: 4.5em;
  margin-right: 4px;
  color: var(--teal);
  font-weight: 950;
}

.oxide-taxonomy-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.oxide-compare {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px;
  margin: 16px 0 12px;
}

.oxide-compare article {
  min-width: 0;
  padding: 16px;
  border: 1px solid rgba(15, 118, 110, 0.16);
  border-radius: 8px;
  background: linear-gradient(180deg, rgba(238, 248, 245, 0.72), rgba(255, 255, 255, 0.96));
}

.oxide-compare h6 {
  margin: 0 0 10px;
  color: var(--ink);
  font-size: 17px;
  font-weight: 950;
}

.oxide-compare p {
  margin: 0 0 8px;
  color: var(--muted);
  font-size: 14px;
  line-height: 1.72;
}

.oxide-compare p:last-child {
  margin-bottom: 0;
}

.oxide-compare strong {
  display: inline-block;
  min-width: 5.6em;
  margin-right: 4px;
  color: var(--teal);
  font-weight: 950;
}

.chem-equation {
  display: inline-block;
  white-space: nowrap;
  word-break: keep-all;
  overflow-wrap: normal;
}

.knowledge-image-strip {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px;
  margin-top: 16px;
}

.knowledge-image-strip-single {
  grid-template-columns: minmax(0, 1fr);
}

.knowledge-image-strip-centered {
  grid-template-columns: minmax(0, 1fr);
  justify-items: center;
}

.knowledge-figure {
  margin: 0;
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: linear-gradient(180deg, #fff, #f8fbfa);
  box-shadow: 0 10px 26px rgba(26, 53, 49, 0.08);
}

.knowledge-figure-narrow {
  max-width: 420px;
}

.knowledge-figure-centered {
  width: min(100%, 380px);
}

.knowledge-figure-cross {
  width: min(100%, 920px);
}

.knowledge-figure img {
  display: block;
  width: 100%;
  height: auto;
  max-height: 260px;
  object-fit: contain;
}

.knowledge-figure-wide img {
  max-height: 430px;
}

.knowledge-figure-centered img {
  max-height: 325px;
}

.knowledge-figure-cross img {
  max-height: 430px;
}

.knowledge-figure figcaption {
  margin-top: 10px;
  color: var(--muted);
  font-size: 13px;
  font-weight: 850;
  text-align: center;
}

.classification-visuals {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px;
  align-content: start;
  padding: clamp(18px, 2.4vw, 28px);
  background:
    linear-gradient(180deg, rgba(238, 247, 244, 0.92), rgba(248, 251, 250, 0.96)),
    repeating-linear-gradient(90deg, transparent 0 42px, rgba(15, 118, 110, 0.035) 42px 43px);
}

.visual-card {
  margin: 0;
  padding: 12px;
  border: 1px solid rgba(217, 230, 226, 0.94);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.94);
  box-shadow: 0 10px 26px rgba(26, 53, 49, 0.08);
}

.visual-card-wide {
  grid-column: 1 / -1;
}

.visual-card img {
  display: block;
  width: 100%;
  height: auto;
  max-height: 238px;
  object-fit: contain;
}

.visual-card-wide img {
  max-height: 310px;
}

.visual-card figcaption {
  margin-top: 8px;
  color: var(--muted);
  font-size: 13px;
  font-weight: 850;
  text-align: center;
}

.tag-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 14px;
}

.tag-row strong,
.tag-row em {
  display: inline-flex;
  align-items: center;
  min-height: 28px;
  padding: 0 10px;
  border-radius: 999px;
  font-size: 13px;
  font-style: normal;
  font-weight: 850;
}

.tag-row strong {
  color: #fff;
  background: var(--teal);
}

.tag-row em {
  color: var(--teal);
  background: rgba(15, 118, 110, 0.1);
}

.tag-row.difficult strong {
  background: var(--rose);
}

.tag-row.difficult em {
  color: var(--rose);
  background: rgba(207, 77, 104, 0.1);
}

.lesson-links {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 16px;
}

.lesson-card-link {
  display: block;
  color: inherit;
  text-decoration: none;
}

.lesson-links a {
  display: inline-flex;
  align-items: center;
  min-height: 38px;
  padding: 0 12px;
  border: 1px solid rgba(15, 118, 110, 0.18);
  border-radius: 999px;
  color: var(--teal);
  background: rgba(238, 248, 245, 0.9);
  font-size: 13px;
  font-weight: 900;
  white-space: nowrap;
}

.lesson-links span {
  display: inline-flex;
  align-items: center;
  min-height: 38px;
  padding: 0 12px;
  border: 1px solid rgba(15, 118, 110, 0.18);
  border-radius: 999px;
  color: var(--teal);
  background: rgba(238, 248, 245, 0.9);
  font-size: 13px;
  font-weight: 900;
  white-space: nowrap;
}

.lesson-links a:hover {
  border-color: rgba(15, 118, 110, 0.34);
  color: #fff;
  background: linear-gradient(135deg, var(--teal), var(--blue));
}

.lesson-links span:hover {
  border-color: rgba(15, 118, 110, 0.34);
  color: #fff;
  background: linear-gradient(135deg, var(--teal), var(--blue));
}

.study-hero {
  display: grid;
  grid-template-columns: minmax(0, 0.9fr) minmax(420px, 0.72fr);
  gap: clamp(28px, 5vw, 72px);
  align-items: center;
  min-height: calc(100vh - 76px);
  padding: clamp(54px, 7vw, 96px) clamp(18px, 5vw, 76px) clamp(48px, 6vw, 78px);
  background:
    linear-gradient(90deg, rgba(248, 251, 250, 0.98) 0%, rgba(248, 251, 250, 0.92) 47%, rgba(248, 251, 250, 0.48) 100%),
    url("../assets/compulsory1-hero-photo.jpg") right center / min(56vw, 900px) auto no-repeat,
    linear-gradient(135deg, #f7fbfa 0%, #eef7f5 58%, #f8f5ec 100%);
  box-shadow: inset 0 -1px 0 rgba(15, 118, 110, 0.12);
}

.study-hero-copy {
  max-width: 780px;
}

.section-kicker {
  display: inline-flex;
  align-items: center;
  min-height: 30px;
  margin-bottom: 14px;
  padding: 0 12px;
  border: 1px solid rgba(15, 118, 110, 0.18);
  border-radius: 999px;
  color: var(--teal);
  background: rgba(238, 248, 245, 0.86);
  font-size: 13px;
  font-weight: 900;
}

.study-hero h1 {
  max-width: 820px;
  font-size: clamp(46px, 5.4vw, 76px);
}

.study-hero p {
  max-width: 700px;
  color: var(--muted);
  font-size: clamp(17px, 1.8vw, 22px);
  font-weight: 720;
}

.study-start-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
  align-self: stretch;
  align-content: end;
}

.study-start-grid a,
.course-card,
.chapter-entry,
.mistake-grid article,
.practice-list article,
.tool-card-grid a,
.roadmap-card,
.tool-panel,
.download-grid article,
.timeline-grid article,
.knowledge-map article,
.explain-grid article,
.example-list article,
.lab-steps article,
.lab-template-grid article,
.lab-detail-grid article {
  border: 1px solid var(--line);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.94);
  box-shadow: var(--soft-shadow);
}

.study-start-grid a {
  min-height: 180px;
  padding: 22px;
  transition: transform 180ms ease, border-color 180ms ease, box-shadow 180ms ease;
}

.study-start-grid a:hover,
.chapter-entry:hover,
.tool-card-grid a:hover,
.practice-list article:hover {
  border-color: rgba(15, 118, 110, 0.32);
  transform: translateY(-3px);
}

.study-start-grid strong,
.tool-card-grid strong {
  display: block;
  margin-bottom: 10px;
  font-size: 23px;
  line-height: 1.2;
}

.study-start-grid span,
.tool-card-grid span {
  display: block;
  color: var(--muted);
  font-weight: 760;
  line-height: 1.55;
}

.dashboard-strip {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1px;
  margin: 0 clamp(18px, 5vw, 76px);
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--line);
  box-shadow: var(--soft-shadow);
  transform: translateY(-22px);
}

.dashboard-strip article {
  min-height: 150px;
  padding: 24px;
  background: var(--paper);
}

.dashboard-strip span,
.course-card span,
.chapter-entry span,
.mistake-grid span,
.practice-list span,
.roadmap-card > span,
.tool-panel-head span,
.download-grid span,
.timeline-grid span,
.lab-detail-grid span,
.explain-grid span {
  display: block;
  margin-bottom: 10px;
  color: var(--teal);
  font-size: 13px;
  font-weight: 900;
}

.dashboard-strip strong {
  display: block;
  min-height: 56px;
  font-size: clamp(19px, 2vw, 24px);
  line-height: 1.28;
}

.dashboard-strip a,
.course-card a:not(.primary-action):not(.secondary-action),
.practice-list a,
.download-grid a {
  display: inline-flex;
  margin-top: 14px;
  color: var(--teal);
  font-weight: 900;
}

.course-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.35fr) repeat(3, minmax(0, 1fr));
  gap: 16px;
  margin-top: 30px;
}

.course-card {
  display: flex;
  min-height: 280px;
  padding: 24px;
  flex-direction: column;
  justify-content: space-between;
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.98), rgba(247, 252, 250, 0.96));
}

.course-card.featured {
  color: #fff;
  border-color: rgba(15, 118, 110, 0.26);
  background:
    linear-gradient(135deg, rgba(15, 118, 110, 0.96), rgba(38, 120, 215, 0.88)),
    url("../assets/matter-classification-tree.png") center / cover no-repeat;
}

.course-card.featured span,
.course-card.featured p {
  color: rgba(255, 255, 255, 0.82);
}

.course-card.featured .primary-action {
  color: var(--teal);
  background: #fff;
  box-shadow: none;
}

.chapter-entry-grid,
.mistake-grid,
.tool-card-grid,
.download-grid,
.timeline-grid,
.knowledge-map,
.explain-grid,
.lab-steps,
.lab-template-grid,
.lab-detail-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
  margin-top: 30px;
}

.chapter-entry,
.tool-card-grid a,
.mistake-grid article,
.download-grid article,
.timeline-grid article,
.knowledge-map article,
.explain-grid article,
.lab-steps article,
.lab-template-grid article,
.lab-detail-grid article {
  padding: 24px;
}

.chapter-entry {
  display: block;
  min-height: 210px;
}

.chapter-entry strong {
  display: block;
  margin-bottom: 10px;
  font-size: clamp(24px, 3vw, 34px);
  line-height: 1.16;
}

.chapter-entry p,
.mistake-grid p,
.course-card p,
.roadmap-card p,
.download-grid p,
.timeline-grid p,
.knowledge-map p,
.explain-grid p,
.example-list p,
.lab-steps p,
.lab-template-grid p,
.lab-detail-grid p,
.tool-panel-head p {
  color: var(--muted);
}

.mistake-grid {
  grid-template-columns: repeat(4, 1fr);
}

.mistake-grid article {
  min-height: 210px;
  background: linear-gradient(180deg, #fff, #f8fbfa);
}

.practice-list {
  display: grid;
  gap: 12px;
  margin-top: 30px;
}

.practice-list article {
  display: grid;
  grid-template-columns: 180px minmax(0, 1fr) auto;
  gap: 18px;
  align-items: center;
  min-height: 88px;
  padding: 18px 22px;
  background: #fff;
}

.practice-list strong {
  font-size: clamp(18px, 2vw, 24px);
  line-height: 1.25;
}

.tool-card-grid {
  grid-template-columns: repeat(4, 1fr);
}

.compact-hero {
  min-height: 300px;
  display: flex;
  align-items: center;
}

.course-roadmap {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
  margin-top: 30px;
}

.roadmap-card {
  display: flex;
  min-height: 320px;
  padding: 24px;
  flex-direction: column;
  justify-content: space-between;
}

.roadmap-card.active {
  border-color: rgba(15, 118, 110, 0.32);
  background: linear-gradient(180deg, #ffffff, #eef8f5);
}

.bank-filter-panel {
  display: grid;
  gap: 16px;
  margin-top: 24px;
  padding: 22px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.94);
  box-shadow: var(--soft-shadow);
}

.bank-filter-panel div {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  align-items: center;
}

.bank-filter-panel strong {
  width: 64px;
  color: var(--ink);
}

.enhanced-bank {
  align-items: stretch;
}

.enhanced-bank .question-card {
  min-height: 330px;
  display: flex;
  flex-direction: column;
}

.enhanced-bank .answer-toggle,
.enhanced-bank .mistake-toggle {
  align-self: flex-start;
}

.mistake-toggle {
  min-height: 38px;
  margin-top: auto;
  padding: 0 14px;
  border: 1px solid rgba(216, 138, 22, 0.28);
  border-radius: 8px;
  color: #9b5f08;
  background: #fff8e8;
  font-weight: 900;
}

.question-card.is-marked {
  border-color: rgba(216, 138, 22, 0.55);
  background: linear-gradient(180deg, #fff, #fff8e8);
}

.question-card.is-marked .mistake-toggle {
  color: #fff;
  background: var(--amber);
}

.tools-workbench {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
}

.tool-panel {
  padding: 24px;
  background: #fff;
}

.tool-panel-head h2 {
  margin-bottom: 8px;
  font-size: clamp(25px, 3vw, 36px);
}

.tools-workbench .tool-form {
  grid-template-columns: repeat(2, minmax(0, 1fr));
  margin-top: 18px;
}

.tool-choice-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 18px;
}

.tool-choice-row button {
  min-height: 42px;
  padding: 0 13px;
  border: 1px solid var(--line);
  border-radius: 8px;
  color: var(--ink);
  background: #fff;
  font-weight: 900;
}

.tool-choice-row button.active,
.tool-choice-row button:hover {
  border-color: rgba(15, 118, 110, 0.34);
  color: var(--teal);
  background: #eef8f5;
}

.quick-table,
.solubility-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
  margin-top: 18px;
}

.quick-table span,
.solubility-grid span {
  min-height: 44px;
  padding: 10px 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--paper-soft);
  font-weight: 850;
}

.download-grid {
  grid-template-columns: repeat(4, 1fr);
}

.timeline-grid {
  grid-template-columns: repeat(6, 1fr);
}

.timeline-grid article {
  min-height: 250px;
}

.timeline-grid span {
  display: inline-grid;
  width: 46px;
  height: 38px;
  place-items: center;
  border-radius: 8px;
  color: #fff;
  background: var(--teal);
}

.chapter-page .section {
  padding-top: clamp(46px, 7vw, 84px);
  padding-bottom: clamp(46px, 7vw, 84px);
}

.chapter-hero {
  padding: clamp(34px, 5vw, 58px) clamp(18px, 5vw, 76px) clamp(26px, 4vw, 42px);
  border-bottom: 1px solid rgba(211, 226, 222, 0.82);
  background: linear-gradient(180deg, #ffffff, #f8fbfa);
}

.chapter-hero span {
  display: block;
  margin-bottom: 10px;
  color: var(--teal);
  font-size: 13px;
  font-weight: 950;
}

.chapter-hero h1 {
  margin: 0;
  font-size: clamp(42px, 7vw, 82px);
  line-height: 1.05;
}

.chapter-hero p {
  margin-top: 14px;
  max-width: 720px;
  color: var(--muted);
  font-size: clamp(17px, 2vw, 22px);
}

.chapter-subnav {
  position: sticky;
  top: 76px;
  z-index: 12;
  display: flex;
  flex-wrap: wrap;
  gap: clamp(18px, 3vw, 34px);
  padding: 0 clamp(18px, 5vw, 76px);
  border-bottom: 1px solid rgba(211, 226, 222, 0.86);
  background: rgba(255, 255, 255, 0.96);
  backdrop-filter: blur(12px);
}

.chapter-subnav a {
  position: relative;
  min-height: 48px;
  padding: 14px 0 12px;
  color: var(--teal);
  font-weight: 900;
  letter-spacing: 0;
}

.chapter-subnav a::after {
  position: absolute;
  right: 0;
  bottom: -1px;
  left: 0;
  height: 2px;
  border-radius: 99px;
  background: transparent;
  content: "";
}

.chapter-subnav a:hover::after,
.chapter-subnav a:first-child::after {
  background: var(--teal);
}

.knowledge-map {
  grid-template-columns: repeat(3, 1fr);
}

.explain-grid {
  grid-template-columns: repeat(3, 1fr);
}

.example-list {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 16px;
  margin-top: 30px;
}

.example-list article {
  min-height: 260px;
  padding: 24px;
}

.lab-steps {
  grid-template-columns: repeat(2, 1fr);
}

.lab-template-grid {
  grid-template-columns: repeat(3, 1fr);
}

.lab-template-grid strong {
  display: block;
  margin-bottom: 8px;
  font-size: 20px;
}

.lab-detail-grid {
  grid-template-columns: repeat(4, 1fr);
}

.lab-detail-grid article:last-child {
  grid-column: span 2;
}

.site-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  padding: 30px clamp(18px, 5vw, 76px);
  border-top: 1px solid var(--line);
  color: var(--muted);
  background: var(--paper);
}

.site-footer p {
  margin-bottom: 0;
}

.site-footer a {
  color: var(--teal);
  font-weight: 900;
}

@keyframes toolPaneIn {
  from {
    opacity: 0;
    transform: translateY(8px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes periodicPaneIn {
  from {
    opacity: 0;
    transform: translateY(12px) scale(0.985);
  }

  to {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
}

@keyframes homeLightSweep {
  from {
    transform: translate3d(-8%, -2%, 0) rotate(0.001deg);
  }

  to {
    transform: translate3d(8%, 2%, 0) rotate(0.001deg);
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }

  .reveal-ready .reveal {
    opacity: 1;
    filter: none;
    transform: none;
  }

  .home-landing::before {
    animation: none;
  }
}

@media (max-width: 1080px) {
  .dispersion-intro-grid,
  .dispersion-detail-grid {
    grid-template-columns: minmax(0, 1fr);
  }

  .dispersion-property-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .hero,
  .practice-layout,
  .lab-layout,
  .study-hero {
    grid-template-columns: 1fr;
  }

  .hero {
    min-height: auto;
  }

  .dashboard-visual {
    min-height: auto;
  }

  .module-grid,
  .path-grid,
  .knowledge-grid,
  .syllabus-grid,
  .course-grid,
  .course-roadmap,
  .mistake-grid,
  .tool-card-grid,
  .download-grid,
  .timeline-grid,
  .lab-detail-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .learning-hub,
  .drill-grid,
  .chapter-entry-grid,
  .classification-board,
  .lab-template-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .classification-board {
    grid-template-columns: 1fr;
  }

  .tool-column-head {
    grid-column: 1 / -1;
  }

  .study-hero {
    min-height: auto;
    background:
      linear-gradient(180deg, rgba(248, 251, 250, 0.99) 0%, rgba(248, 251, 250, 0.94) 58%, rgba(248, 251, 250, 0.62) 100%),
      url("../assets/compulsory1-hero-photo.jpg") center bottom / min(980px, 130vw) auto no-repeat,
      linear-gradient(135deg, #f7fffc, #eef8f5 52%, #f8f5ec);
    padding-bottom: clamp(240px, 44vw, 430px);
  }

  .tools-workbench,
  .knowledge-map,
  .explain-grid {
    grid-template-columns: 1fr;
  }

  .lab-detail-grid article:last-child {
    grid-column: span 1;
  }

  .home-entry-grid {
    width: min(100%, 900px);
  }

  .book-cover-page .home-landing {
    padding-left: clamp(76px, 9vw, 108px);
  }

  .book-shelf {
    --book-width: clamp(174px, 20vw, 214px);
    --book-overlap: clamp(-110px, -9.5vw, -82px);
    min-height: clamp(360px, 52vh, 500px);
  }
}

@media (max-width: 760px) {
  .dispersion-intro-grid,
  .dispersion-detail-grid,
  .dispersion-trap-list {
    grid-template-columns: minmax(0, 1fr);
  }

  .dispersion-intro-grid,
  .dispersion-detail-grid {
    gap: 22px;
  }

  .dispersion-definition-list div,
  .dispersion-type-list li {
    grid-template-columns: minmax(0, 1fr);
    gap: 4px;
  }

  .dispersion-table-head,
  .dispersion-properties-head {
    display: block;
    margin-top: 46px;
  }

  .dispersion-table-head > p,
  .dispersion-properties-head > p {
    margin-top: 10px;
    text-align: left;
  }

  .dispersion-table-wrap {
    margin-right: -18px;
    margin-left: -18px;
    border-right: 0;
    border-left: 0;
    border-radius: 0;
  }

  .point-body .dispersion-table-wrap {
    margin-right: 0;
    margin-left: 0;
    border-right: 1px solid var(--line);
    border-left: 1px solid var(--line);
    border-radius: 8px;
  }

  .dispersion-table th,
  .dispersion-table td {
    padding: 13px 12px;
  }

  .dispersion-property-grid {
    grid-template-columns: minmax(0, 1fr);
  }

  .dispersion-trap-list {
    gap: 18px;
    margin-right: -2px;
    margin-left: -2px;
    padding: 22px;
  }

  .site-header {
    align-items: flex-start;
    flex-wrap: wrap;
  }

  .nav-toggle {
    display: inline-flex;
    align-items: center;
  }

  .site-nav {
    display: none;
    width: 100%;
    justify-content: flex-start;
  }

  .site-nav.is-open {
    display: flex;
  }

  .hero-actions,
  .site-footer {
    align-items: stretch;
    flex-direction: column;
  }

  .primary-action,
  .secondary-action {
    width: 100%;
  }

  .metric-strip,
  .learning-hub,
  .module-grid,
  .path-grid,
  .knowledge-grid,
  .equation-board,
  .exam-grid,
  .answers,
    .syllabus-grid,
    .question-bank,
    .lesson-grid,
    .classification-board,
    .classification-visuals,
    .knowledge-image-strip,
    .notes-grid,
    .drill-grid,
    .study-start-grid,
    .home-entry-grid,
    .dashboard-strip,
    .course-grid,
    .chapter-entry-grid,
    .mistake-grid,
    .practice-list,
    .tool-card-grid,
    .course-roadmap,
    .download-grid,
    .timeline-grid,
    .knowledge-map,
    .explain-grid,
    .example-list,
    .lab-steps,
    .lab-template-grid,
    .lab-detail-grid,
    .tools-workbench,
    .quick-table,
    .solubility-grid,
    .tools-workbench .tool-form {
    grid-template-columns: 1fr;
  }

  .study-hero {
    padding-top: 42px;
    padding-bottom: clamp(210px, 60vw, 330px);
  }

  .study-hero h1 {
    font-size: clamp(40px, 13vw, 62px);
  }

  .study-start-grid a,
  .course-card,
  .chapter-entry,
  .mistake-grid article,
  .tool-card-grid a,
  .roadmap-card,
  .tool-panel,
  .download-grid article,
  .timeline-grid article,
  .knowledge-map article,
  .explain-grid article,
  .example-list article,
  .lab-steps article,
  .lab-template-grid article,
  .lab-detail-grid article {
    min-height: auto;
    padding: 20px;
  }

  .dashboard-strip {
    transform: none;
    margin-top: 18px;
  }

  .dashboard-strip strong {
    min-height: 0;
  }

  .home-landing-page {
    overflow-y: auto;
  }

  .home-landing {
    min-height: 100svh;
    padding: 78px 18px 86px;
  }

  .book-cover-page {
    overflow-x: hidden;
  }

  .book-cover-page .home-landing {
    align-items: stretch;
    min-height: 100svh;
    padding: 24px 0 32px;
  }

  .book-rail {
    position: relative;
    top: auto;
    left: auto;
    display: flex;
    width: auto;
    margin: 0 18px 18px;
    overflow-x: auto;
    transform: none;
    scrollbar-width: none;
  }

  .book-rail::-webkit-scrollbar {
    display: none;
  }

  .book-rail a {
    min-width: 62px;
    min-height: 38px;
    padding: 0 8px;
  }

  .book-cover-hero {
    align-content: center;
    min-height: calc(100svh - 92px);
    gap: 18px;
  }

  .book-cover-title {
    padding: 0 18px;
  }

  .book-cover-title h1 {
    font-size: clamp(42px, 18vw, 70px);
  }

  .book-shelf {
    --book-width: min(54vw, 190px);
    --book-overlap: 0px;
    justify-content: flex-start;
    min-height: 430px;
    margin-top: 4px;
    padding: 20px 18px 56px;
    overflow-x: auto;
    scroll-snap-type: x mandatory;
    scrollbar-width: none;
  }

  .book-shelf::-webkit-scrollbar {
    display: none;
  }

  .book-shelf::before {
    right: 18px;
    left: 18px;
    bottom: 18px;
  }

  .book-card {
    --book-angle: -18deg;
    --neighbor-shift: 0px;
    margin-inline: 0 42px;
    scroll-snap-align: center;
    transform: translateY(0);
  }

  .book-visual img {
    filter: none;
  }

  .book-card:hover,
  .book-card:focus,
  .book-card:focus-visible {
    transform: translateY(-12px) scale(1.02);
  }

  .book-card:hover .book-visual,
  .book-card:focus .book-visual,
  .book-card:focus-visible .book-visual {
    transform: rotateY(-12deg);
  }

  .book-pages,
  .book-card:hover .book-pages,
  .book-card:focus .book-pages,
  .book-card:focus-visible .book-pages {
    top: 5px;
    bottom: 80px;
    left: calc(100% - 8px);
  }

  .book-caption {
    min-height: 66px;
    margin-top: 12px;
    opacity: 1;
    transform: none;
  }

  .home-entry-card {
    min-height: 128px;
    padding: 22px;
  }

  .home-entry-card:hover,
  .home-entry-card:focus-visible {
    transform: translateY(-3px);
  }

  .practice-list article {
    display: block;
  }

  .bank-filter-panel {
    padding: 18px;
  }

  .bank-filter-panel strong {
    width: 100%;
  }

  .chapter-subnav {
    position: static;
  }

  .chapter-hero {
    padding-top: 30px;
    padding-bottom: 26px;
    background: linear-gradient(180deg, #ffffff, #f8fbfa);
  }

  .chapter-frame,
  .classification-knowledge,
  .classification-visuals,
  .visual-card {
    max-width: 100%;
    min-width: 0;
  }

  .classification-knowledge {
    overflow: hidden;
  }

  .classification-knowledge > p,
  .knowledge-block p {
    word-break: break-word;
    overflow-wrap: anywhere;
  }

  .floating-toolbox {
    --toolbox-panel-gap: 64px;
    right: 18px;
  }

  .toolbox-toggle {
    width: 54px;
    height: 54px;
  }

  .floating-tool-panel {
    position: fixed;
    top: auto;
    right: 18px;
    bottom: 92px;
    left: 18px;
    width: auto;
    max-height: calc(100vh - 28px);
    transform: translateY(12px);
  }

  .floating-toolbox.has-active-tool .floating-tool-panel,
  .floating-toolbox.opens-right.has-active-tool .floating-tool-panel {
    transform: translateY(0);
  }

  .floating-toolbox.is-periodic-modal-open .floating-tool-panel {
    inset: 0;
    padding: 14px;
  }

  .floating-toolbox.is-periodic-modal-open .periodic-pane {
    width: 100%;
    height: calc(100vh - 28px);
    max-height: none;
    padding: 14px;
  }

  .floating-toolbox.is-periodic-modal-open .periodic-pane .mini-title {
    flex: 0 0 auto;
    gap: 8px;
  }

  .floating-toolbox.is-periodic-modal-open .periodic-pane .mini-title strong {
    display: none;
  }

  .periodic-embed-wrap {
    margin-top: 10px;
  }

  .periodic-embed {
    min-width: 920px;
    min-height: 560px;
  }

  .periodic-table {
    grid-template-columns: 42px repeat(18, 58px);
    grid-template-rows: 40px repeat(9, 72px);
    min-width: 1178px;
  }

  .period-label {
    font-size: 10px;
  }

  .element {
    grid-template-rows: 13px 23px 15px 13px;
    padding: 5px 6px;
  }

  .element b {
    font-size: 18px;
  }

  .element em {
    font-size: 8px;
  }

  .mini-tool-form,
  .mini-checklist {
    grid-template-columns: 1fr;
  }

  .chapter-title {
    align-items: flex-start;
    flex-direction: column;
  }

  .chapter-title h3 {
    text-align: left;
  }

  .floating-panel {
    position: static;
    width: 100%;
    margin-top: 12px;
  }

  .page-hero {
    background:
      linear-gradient(180deg, rgba(255, 255, 255, 0.94), rgba(255, 255, 255, 0.94)),
      url("../assets/chemistry-hero.svg") center bottom / 680px auto no-repeat;
  }

  .compulsory-hero {
    grid-template-columns: 1fr;
    min-height: auto;
    padding-bottom: clamp(230px, 54vw, 340px);
    background:
      linear-gradient(180deg, rgba(248, 253, 251, 0.99) 0%, rgba(248, 253, 251, 0.96) 45%, rgba(248, 253, 251, 0.72) 68%, rgba(248, 253, 251, 0.18) 100%),
      url("../assets/compulsory1-opening-lab.jpg") 70% bottom / auto 100% no-repeat,
      linear-gradient(135deg, #f7fffc, #eef8f5 48%, #f8f5ec);
  }

  .compulsory-hero-copy h1 {
    font-size: clamp(42px, 13vw, 68px);
  }
}

@media (max-width: 760px) {
  html,
  body,
  .chapter-page {
    max-width: 100%;
    overflow-x: hidden;
  }

  .classification-board,
  .classification-knowledge,
  .classification-visuals,
  .visual-card {
    width: 100%;
    max-width: 100%;
    min-width: 0;
  }

  .classification-board,
  .classification-visuals {
    grid-template-columns: minmax(0, 1fr) !important;
  }

  .knowledge-image-strip {
    grid-template-columns: minmax(0, 1fr);
  }

  .taxonomy-grid {
    grid-template-columns: minmax(0, 1fr);
  }

  .oxide-taxonomy-grid,
  .oxide-compare {
    grid-template-columns: minmax(0, 1fr);
  }
  .taxonomy-card-wide {
    grid-column: span 1;
  }

  .chem-equation {
    white-space: normal;
  }

  .classification-knowledge p,
  .classification-knowledge strong,
  .point-body p,
  .taxonomy-card p,
  .taxonomy-card strong,
  .oxide-compare p,
  .oxide-compare strong,
  .visual-card figcaption,
  .knowledge-figure figcaption {
    max-width: 100%;
    white-space: normal;
    word-break: break-word;
    overflow-wrap: anywhere;
  }

  .lesson-note-heading {
    align-items: flex-start;
    flex-direction: column;
  }

  .knowledge-point {
    grid-template-columns: 1fr;
    gap: 10px;
    padding: 20px 0;
  }

  .point-number {
    width: 38px;
    height: 34px;
  }
}