:root {
  color-scheme: light;
  --paper: #f7f4ea;
  --surface: #fffdf7;
  --surface-strong: #fff5dc;
  --ink: #20312f;
  --muted: #60706c;
  --line: #ded7c8;
  --teal: #1f766d;
  --teal-soft: #dff2ed;
  --coral: #d86143;
  --coral-soft: #ffe1d7;
  --gold: #b98213;
  --gold-soft: #fff0bf;
  --blue: #3d617c;
  --blue-soft: #dcecf6;
  --shadow: 0 18px 45px rgba(32, 49, 47, 0.12);
  --radius: 8px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  overflow-x: hidden;
  background: var(--paper);
  color: var(--ink);
  font-family: "Segoe UI", "Apple SD Gothic Neo", "Malgun Gothic", system-ui, sans-serif;
  letter-spacing: 0;
}

button,
summary {
  font: inherit;
}

button {
  border: 0;
  cursor: pointer;
}

.app-shell {
  min-height: 100vh;
  display: grid;
  grid-template-columns: 184px minmax(0, 1fr);
  grid-template-rows: 70px minmax(0, 1fr) 72px;
}

.topbar {
  grid-column: 1 / -1;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  padding: 0 22px;
  border-bottom: 1px solid var(--line);
  background: rgba(255, 253, 247, 0.92);
  backdrop-filter: blur(12px);
  z-index: 5;
}

.brand {
  display: flex;
  align-items: center;
  min-width: 0;
  gap: 12px;
}

.brand-mark {
  width: 34px;
  height: 34px;
  border-radius: 50%;
  border: 3px solid var(--teal);
  background:
    radial-gradient(circle at 48% 50%, var(--ink) 0 4px, transparent 5px),
    radial-gradient(circle at 50% 50%, #f8d36f 0 11px, transparent 12px),
    var(--teal-soft);
  box-shadow: inset 0 0 0 4px #fffdf7;
  flex: 0 0 auto;
}

.brand strong {
  display: block;
  font-size: 17px;
  line-height: 1.2;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.brand span:not(.brand-mark) {
  display: block;
  color: var(--muted);
  font-size: 12px;
  margin-top: 3px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.brand > div {
  min-width: 0;
}

.top-actions {
  display: flex;
  gap: 8px;
}

.subject-tabs {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  min-width: 0;
  padding: 5px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #f1eadc;
}

.subject-tab {
  min-height: 34px;
  padding: 7px 11px;
  border-radius: 6px;
  color: var(--muted);
  background: transparent;
  font-size: 13px;
  font-weight: 900;
  white-space: nowrap;
}

.subject-tab.active {
  color: white;
  background: var(--teal);
}

.icon-button,
.nav-button {
  display: inline-grid;
  place-items: center;
  color: var(--ink);
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  transition: transform 160ms ease, background 160ms ease, border-color 160ms ease;
}

.icon-button {
  width: 42px;
  height: 42px;
}

.nav-button {
  width: 48px;
  height: 48px;
  background: var(--ink);
  color: white;
}

.icon-button:hover,
.nav-button:hover {
  transform: translateY(-1px);
  border-color: var(--teal);
}

.icon-button[aria-pressed="true"] {
  background: var(--teal-soft);
  border-color: var(--teal);
}

.icon-button svg,
.nav-button svg {
  width: 20px;
  height: 20px;
}

.slide-rail {
  grid-row: 2 / 4;
  grid-column: 1;
  padding: 16px 12px 18px;
  border-right: 1px solid var(--line);
  overflow-y: auto;
  background: #f1eadc;
}

.slide-rail::-webkit-scrollbar {
  width: 6px;
  height: 6px;
}

.slide-rail::-webkit-scrollbar-thumb {
  background: #c6bba8;
  border-radius: 999px;
}

.rail-button {
  width: 100%;
  display: grid;
  grid-template-columns: 28px 1fr;
  align-items: center;
  gap: 8px;
  text-align: left;
  padding: 9px 8px;
  margin-bottom: 7px;
  color: var(--ink);
  background: transparent;
  border: 1px solid transparent;
  border-radius: var(--radius);
}

.rail-button .rail-num {
  display: grid;
  place-items: center;
  width: 28px;
  height: 28px;
  border-radius: 50%;
  font-size: 12px;
  font-weight: 800;
  color: var(--teal);
  background: var(--teal-soft);
}

.rail-button span:last-child {
  min-width: 0;
  font-size: 12px;
  line-height: 1.25;
}

.rail-button:hover,
.rail-button.active {
  background: var(--surface);
  border-color: var(--line);
}

.rail-button.active .rail-num {
  color: white;
  background: var(--teal);
}

.deck {
  grid-column: 2;
  grid-row: 2;
  min-width: 0;
  min-height: 0;
  overflow: hidden;
}

.slide {
  height: 100%;
  overflow-y: auto;
  padding: 30px clamp(18px, 4vw, 54px) 34px;
}

.slide[data-theme="lens"] {
  background: linear-gradient(180deg, #fffaf0 0%, #f7f4ea 100%);
}

.slide[data-theme="orbit"] {
  background: linear-gradient(180deg, #f4f7f8 0%, #f7f4ea 100%);
}

.slide[data-theme="tear"] {
  background: linear-gradient(180deg, #eef7f8 0%, #f7f4ea 100%);
}

.slide[data-theme="muscle"] {
  background: linear-gradient(180deg, #fff4ee 0%, #f7f4ea 100%);
}

.slide-head {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: start;
  gap: 24px;
  margin-bottom: 20px;
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  width: fit-content;
  padding: 6px 9px;
  border-radius: 999px;
  color: var(--teal);
  background: var(--teal-soft);
  font-size: 12px;
  font-weight: 800;
}

.slide h1 {
  margin: 12px 0 8px;
  font-size: clamp(30px, 4vw, 52px);
  line-height: 1.05;
  letter-spacing: 0;
}

.slide h2 {
  margin: 0 0 12px;
  font-size: 18px;
}

.lead {
  max-width: 820px;
  margin: 0;
  color: var(--muted);
  font-size: 17px;
  line-height: 1.7;
}

.source-chip {
  justify-self: end;
  display: inline-flex;
  align-items: center;
  min-height: 34px;
  padding: 7px 10px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--surface);
  color: var(--muted);
  font-size: 12px;
  font-weight: 700;
  white-space: nowrap;
}

.slide-layout {
  display: grid;
  grid-template-columns: minmax(260px, 0.76fr) minmax(0, 1.48fr);
  gap: 20px;
  align-items: start;
}

.study-panel,
.visual-panel,
.section-panel,
.question-card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.study-panel,
.visual-panel,
.section-panel {
  padding: 18px;
}

.visual-panel {
  overflow: hidden;
}

.eye-asset {
  display: block;
  width: 100%;
  max-height: 290px;
  object-fit: contain;
}

.summary-list,
.section-list,
.hot-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: grid;
  gap: 10px;
}

.summary-list li,
.section-list li,
.hot-list li {
  position: relative;
  padding-left: 18px;
  color: var(--ink);
  line-height: 1.55;
}

.summary-list li::before,
.section-list li::before,
.hot-list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.72em;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--coral);
}

.section-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
  gap: 14px;
  margin-top: 18px;
}

.section-panel strong {
  display: block;
  margin-bottom: 10px;
  color: var(--teal);
}

.visual-stack {
  display: grid;
  gap: 12px;
}

.mini-diagram {
  min-height: 174px;
  display: grid;
  place-items: center;
  border-radius: var(--radius);
  border: 1px solid var(--line);
  background: #fffaf0;
  overflow: hidden;
}

.diagram-lens {
  width: 210px;
  height: 130px;
  border-radius: 50%;
  background:
    radial-gradient(ellipse at center, rgba(255, 255, 255, 0.8) 0 20%, transparent 21%),
    linear-gradient(90deg, #f7d25f, #fff9d8 50%, #f7d25f);
  border: 5px solid #89630c;
  position: relative;
}

.diagram-lens::before,
.diagram-lens::after {
  content: "";
  position: absolute;
  top: 50%;
  width: 54px;
  height: 4px;
  background: var(--teal);
}

.diagram-lens::before {
  left: -66px;
}

.diagram-lens::after {
  right: -66px;
}

.diagram-flow {
  width: 100%;
  display: grid;
  gap: 8px;
  padding: 12px;
}

.flow-step {
  min-height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 8px;
  border-radius: var(--radius);
  background: var(--blue-soft);
  color: #17384d;
  font-weight: 800;
  text-align: center;
}

.flow-arrow {
  text-align: center;
  color: var(--coral);
  font-weight: 900;
}

.diagram-orbit,
.diagram-muscle,
.diagram-tear {
  width: min(250px, 100%);
  aspect-ratio: 1 / 1;
  position: relative;
}

.diagram-frame,
.diagram-prism,
.diagram-fitting,
.diagram-lensmeter {
  width: min(270px, 100%);
  min-height: 170px;
  position: relative;
}

.diagram-frame {
  display: grid;
  place-items: center;
}

.frame-code {
  display: grid;
  grid-template-columns: 80px 44px 80px;
  align-items: center;
  justify-content: center;
  gap: 8px;
  font-size: 34px;
  font-weight: 900;
  color: var(--ink);
}

.frame-code span {
  display: grid;
  place-items: center;
  min-height: 60px;
  border: 3px solid var(--teal);
  border-radius: var(--radius);
  background: var(--teal-soft);
}

.frame-code small {
  display: grid;
  place-items: center;
  min-height: 44px;
  color: var(--coral);
}

.frame-labels {
  display: flex;
  justify-content: center;
  gap: 18px;
  margin-top: 12px;
  color: var(--muted);
  font-size: 12px;
  font-weight: 800;
}

.diagram-prism {
  display: grid;
  place-items: center;
}

.prism-lens {
  width: 170px;
  height: 112px;
  clip-path: polygon(8% 50%, 92% 10%, 92% 90%);
  background: linear-gradient(90deg, var(--coral-soft), #fffdf7);
  border: 4px solid var(--coral);
}

.prism-formula {
  margin-top: 12px;
  text-align: center;
  color: var(--teal);
  font-size: 24px;
  font-weight: 900;
}

.diagram-fitting {
  display: grid;
  gap: 9px;
  align-content: center;
}

.fit-step {
  min-height: 38px;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 8px;
  border-radius: var(--radius);
  background: var(--coral-soft);
  color: #73321e;
  font-weight: 900;
  text-align: center;
}

.diagram-lensmeter {
  display: grid;
  place-items: center;
}

.meter-body {
  width: 190px;
  height: 128px;
  border-radius: 8px 8px 26px 26px;
  border: 5px solid var(--blue);
  background: var(--blue-soft);
  position: relative;
}

.meter-body::before {
  content: "";
  position: absolute;
  left: 50%;
  top: 22px;
  width: 76px;
  height: 76px;
  transform: translateX(-50%);
  border-radius: 50%;
  border: 5px solid var(--teal);
  background: #fffdf7;
}

.meter-body::after {
  content: "D";
  position: absolute;
  left: 50%;
  top: 44px;
  transform: translateX(-50%);
  color: var(--coral);
  font-size: 28px;
  font-weight: 900;
}

.diagram-wave,
.diagram-mirror {
  width: min(270px, 100%);
  min-height: 170px;
  display: grid;
  place-items: center;
  position: relative;
}

.wave-line {
  width: 230px;
  height: 90px;
  background:
    radial-gradient(ellipse at center, transparent 0 55%, var(--teal) 56% 60%, transparent 61%) 0 0 / 76px 90px repeat-x;
  position: relative;
}

.wave-line::after {
  content: "λ";
  position: absolute;
  right: 12px;
  top: 24px;
  color: var(--coral);
  font-size: 34px;
  font-weight: 900;
}

.mirror-plane {
  width: 210px;
  height: 8px;
  background: var(--blue);
  transform: rotate(-24deg);
  border-radius: 999px;
  position: relative;
}

.mirror-plane::before,
.mirror-plane::after {
  content: "";
  position: absolute;
  width: 110px;
  height: 4px;
  background: var(--coral);
  transform-origin: right center;
  right: 54%;
  top: -46px;
}

.mirror-plane::before {
  transform: rotate(42deg);
}

.mirror-plane::after {
  transform: rotate(-42deg);
  top: 50px;
  background: var(--teal);
}

.diagram-orbit {
  border: 7px solid var(--blue);
  clip-path: polygon(50% 5%, 92% 30%, 82% 82%, 50% 97%, 18% 82%, 8% 30%);
  background: #ecf6f8;
}

.diagram-orbit span,
.diagram-muscle span,
.diagram-tear span {
  position: absolute;
  display: grid;
  place-items: center;
  min-width: 44px;
  min-height: 28px;
  padding: 4px 6px;
  border-radius: 999px;
  color: white;
  background: var(--ink);
  font-size: 12px;
  font-weight: 800;
}

.diagram-orbit .top {
  left: 50%;
  top: 8px;
  transform: translateX(-50%);
}

.diagram-orbit .side {
  right: 14px;
  top: 45%;
}

.diagram-orbit .hole {
  left: 50%;
  bottom: 35px;
  transform: translateX(-50%);
  background: var(--coral);
}

.diagram-muscle {
  border: 3px solid var(--line);
  border-radius: 50%;
  background:
    linear-gradient(var(--line), var(--line)) 50% 0 / 2px 100% no-repeat,
    linear-gradient(90deg, var(--line), var(--line)) 0 50% / 100% 2px no-repeat,
    #fffaf0;
}

.diagram-muscle .up {
  left: 50%;
  top: 13px;
  transform: translateX(-50%);
  background: var(--teal);
}

.diagram-muscle .out {
  right: 8px;
  top: 50%;
  transform: translateY(-50%);
  background: var(--coral);
}

.diagram-muscle .in {
  left: 8px;
  top: 50%;
  transform: translateY(-50%);
  background: var(--blue);
}

.diagram-muscle .long {
  left: 50%;
  bottom: 15px;
  transform: translateX(-50%);
  background: var(--gold);
}

.diagram-tear {
  display: grid;
  gap: 8px;
  align-content: center;
}

.tear-layer {
  height: 44px;
  display: grid;
  place-items: center;
  border-radius: var(--radius);
  color: var(--ink);
  font-weight: 900;
}

.tear-layer.lipid {
  background: var(--gold-soft);
}

.tear-layer.aqueous {
  background: var(--blue-soft);
}

.tear-layer.mucin {
  background: var(--teal-soft);
}

.question-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(290px, 1fr));
  gap: 14px;
}

.question-card {
  padding: 16px;
  display: grid;
  gap: 12px;
  min-height: 260px;
}

.question-card.hot {
  border-color: #e0a22a;
  background: linear-gradient(180deg, #fffdf7, #fff8e5);
}

.question-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
}

.pill {
  display: inline-flex;
  align-items: center;
  width: fit-content;
  min-height: 26px;
  padding: 4px 8px;
  border-radius: 999px;
  background: var(--teal-soft);
  color: var(--teal);
  font-size: 12px;
  font-weight: 900;
}

.pill.hot-pill {
  background: var(--gold-soft);
  color: #775006;
}

.question-card h3 {
  margin: 0;
  font-size: 16px;
  line-height: 1.45;
}

.answer-block {
  display: grid;
  gap: 8px;
}

.exam-mode .answer-block {
  display: none;
}

.answer {
  display: flex;
  align-items: baseline;
  gap: 8px;
  padding: 9px 10px;
  border-radius: var(--radius);
  background: var(--teal-soft);
  color: #144d47;
  font-weight: 900;
}

.answer small {
  color: var(--teal);
  font-size: 11px;
  letter-spacing: 0;
}

.note {
  margin: 0;
  color: var(--ink);
  line-height: 1.55;
  font-size: 14px;
}

.note b {
  color: var(--coral);
}

.choices {
  border-top: 1px solid var(--line);
  padding-top: 9px;
}

.choices summary {
  width: fit-content;
  color: var(--blue);
  font-weight: 800;
  cursor: pointer;
  font-size: 13px;
}

.choice-list {
  margin: 8px 0 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 5px;
  color: var(--muted);
  font-size: 13px;
}

.choice-list li.correct {
  color: var(--teal);
  font-weight: 900;
}

.cheat-table {
  width: 100%;
  border-collapse: collapse;
  overflow: hidden;
  border-radius: var(--radius);
  background: var(--surface);
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
}

.cheat-table th,
.cheat-table td {
  padding: 13px 14px;
  text-align: left;
  border-bottom: 1px solid var(--line);
  vertical-align: top;
  line-height: 1.5;
}

.cheat-table th {
  width: 28%;
  color: var(--teal);
  background: var(--teal-soft);
}

.cheat-table tr:last-child th,
.cheat-table tr:last-child td {
  border-bottom: 0;
}

.controlbar {
  grid-column: 2;
  grid-row: 3;
  display: grid;
  grid-template-columns: 54px minmax(0, 1fr) 54px;
  align-items: center;
  gap: 14px;
  padding: 12px clamp(18px, 4vw, 54px);
  border-top: 1px solid var(--line);
  background: rgba(255, 253, 247, 0.92);
  backdrop-filter: blur(12px);
  z-index: 4;
}

.progress-wrap {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 12px;
  align-items: center;
}

.progress-meter {
  height: 9px;
  border-radius: 999px;
  background: #e4dccd;
  overflow: hidden;
}

.progress-meter span {
  display: block;
  height: 100%;
  width: 0;
  background: linear-gradient(90deg, var(--teal), var(--coral));
  border-radius: inherit;
  transition: width 180ms ease;
}

#progressLabel {
  color: var(--muted);
  font-size: 13px;
  font-weight: 800;
  min-width: 52px;
  text-align: right;
}

@media (max-width: 980px) {
  .app-shell {
    grid-template-columns: 1fr;
    grid-template-rows: auto auto minmax(0, 1fr) 72px;
  }

  .slide-rail {
    grid-column: 1;
    grid-row: 2;
    display: flex;
    gap: 8px;
    overflow-x: auto;
    overflow-y: hidden;
    border-right: 0;
    border-bottom: 1px solid var(--line);
    padding: 10px 12px;
  }

  .rail-button {
    width: 128px;
    flex: 0 0 128px;
    margin-bottom: 0;
    grid-template-columns: 24px 1fr;
  }

  .deck {
    grid-column: 1;
    grid-row: 3;
  }

  .controlbar {
    grid-column: 1;
    grid-row: 4;
  }

  .slide-layout {
    grid-template-columns: 1fr;
  }

  .source-chip {
    justify-self: start;
  }

  .subject-tabs {
    order: 3;
    grid-column: 1 / -1;
    width: 100%;
    overflow-x: auto;
  }
}

@media (max-width: 640px) {
  .topbar {
    height: auto;
    min-height: 76px;
    display: grid;
    grid-template-columns: minmax(0, 1fr) auto;
    padding: 0 12px;
    row-gap: 6px;
    padding-top: 8px;
    padding-bottom: 8px;
  }

  .brand strong {
    font-size: 14px;
  }

  .brand span:not(.brand-mark) {
    max-width: 190px;
  }

  .subject-tabs {
    grid-column: 1 / -1;
    justify-content: flex-start;
  }

  .subject-tab {
    font-size: 12px;
    min-height: 32px;
  }

  .top-actions {
    gap: 5px;
  }

  .icon-button {
    width: 38px;
    height: 38px;
  }

  .slide {
    padding: 22px 14px 28px;
  }

  .slide-head {
    grid-template-columns: 1fr;
    gap: 12px;
  }

  .slide h1 {
    font-size: 32px;
  }

  .lead {
    font-size: 15px;
  }

  .question-grid {
    grid-template-columns: 1fr;
  }

  .question-card {
    min-height: auto;
  }

  .controlbar {
    padding: 12px 14px;
  }

  .cheat-table,
  .cheat-table tbody,
  .cheat-table tr,
  .cheat-table th,
  .cheat-table td {
    display: block;
    width: 100%;
  }

  .cheat-table th {
    border-bottom: 0;
  }
}