:root {
  color-scheme: dark;
  --bg: #101211;
  --panel: #191d19;
  --panel-2: #20261f;
  --ink: #f3f1e9;
  --muted: #b8beb4;
  --line: #3a4239;
  --accent: #36d0c5;
  --accent-2: #f0c35a;
  --danger: #ff8b6a;
  --radius: 8px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: Arial, Helvetica, sans-serif;
  background: var(--bg);
  color: var(--ink);
}

a {
  color: var(--accent);
}

button,
textarea,
input {
  font: inherit;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 12px 18px;
  border-bottom: 1px solid var(--line);
  background: #121512;
}

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

.brand-mark {
  width: 38px;
  height: 38px;
  display: grid;
  place-items: center;
  border: 1px solid var(--line);
  border-radius: 7px;
  color: var(--accent);
  font-weight: 800;
  letter-spacing: 0;
}

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

h1 {
  margin-bottom: 2px;
  font-size: 20px;
}

h2 {
  margin-bottom: 8px;
  font-size: 18px;
}

h3 {
  margin-bottom: 8px;
  font-size: 14px;
  color: #ffffff;
}

.topbar p,
.muted,
.case-meta {
  color: var(--muted);
}

.topbar p {
  margin-bottom: 0;
  font-size: 13px;
}

.nav-links {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  font-size: 13px;
}

.nav-links a {
  padding: 7px 10px;
  border: 1px solid var(--line);
  border-radius: 6px;
  text-decoration: none;
  color: var(--ink);
  background: #111511;
}

.page-shell {
  max-width: 1320px;
  margin: 0 auto;
  padding: 18px;
}

.page-shell.wide {
  max-width: 1640px;
}

.intro-grid,
.chapter-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.5fr) minmax(280px, 0.7fr);
  gap: 14px;
}

.panel,
.case-card,
.viewer-panel,
.answer-panel,
.source-panel {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--panel);
}

.panel,
.case-card,
.answer-panel,
.source-panel {
  padding: 14px;
}

.chapter-grid {
  margin-top: 14px;
}

.case-list {
  display: grid;
  gap: 10px;
}

.case-card {
  display: grid;
  gap: 8px;
  text-decoration: none;
  color: var(--ink);
}

.case-card:hover {
  border-color: var(--accent);
}

.case-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.tag {
  display: inline-flex;
  align-items: center;
  min-height: 24px;
  padding: 3px 8px;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--muted);
  font-size: 12px;
}

.tag.important {
  border-color: rgba(54, 208, 197, 0.6);
  color: var(--accent);
}

.case-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 360px;
  gap: 14px;
}

.viewer-panel {
  overflow: hidden;
}

.viewer-head {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 12px;
  padding: 14px;
  border-bottom: 1px solid var(--line);
  background: var(--panel-2);
}

.viewer-head p {
  margin-bottom: 0;
}

.image-stage {
  min-height: 520px;
  display: grid;
  place-items: center;
  padding: 16px;
  background:
    linear-gradient(45deg, rgba(255,255,255,0.025) 25%, transparent 25%, transparent 75%, rgba(255,255,255,0.025) 75%),
    linear-gradient(45deg, rgba(255,255,255,0.025) 25%, transparent 25%, transparent 75%, rgba(255,255,255,0.025) 75%),
    #050606;
  background-position: 0 0, 8px 8px;
  background-size: 16px 16px;
}

.phase-image {
  max-width: 100%;
  max-height: 70vh;
  object-fit: contain;
  background: #000;
}

.scan-stage {
  min-height: 620px;
  padding: 10px;
}

.scan-frame {
  position: relative;
  width: 100%;
  min-height: 590px;
  display: grid;
  place-items: center;
  overflow: hidden;
  background: #000;
  border: 1px solid #242b25;
}

.scan-image {
  width: auto;
  height: auto;
  max-width: min(100%, 780px);
  max-height: 78vh;
  object-fit: contain;
  background: #000;
  transition: transform 120ms ease;
}

.loading-badge {
  position: absolute;
  right: 10px;
  bottom: 10px;
  padding: 5px 8px;
  border: 1px solid rgba(54, 208, 197, 0.45);
  border-radius: 6px;
  color: var(--ink);
  background: rgba(7, 10, 8, 0.84);
  font-size: 12px;
}

.series-placeholder {
  width: min(760px, 100%);
  min-height: 430px;
  display: grid;
  place-items: center;
  align-content: center;
  gap: 12px;
  padding: 28px;
  border: 1px solid #262d26;
  background: #030403;
  text-align: center;
}

.series-placeholder-mark {
  width: 72px;
  height: 72px;
  display: grid;
  place-items: center;
  border: 1px solid var(--line);
  border-radius: 8px;
  color: var(--accent);
  background: #0b100f;
  font-size: 24px;
  font-weight: 800;
}

.series-placeholder h3,
.series-placeholder p {
  margin-bottom: 0;
}

.mock-slider {
  width: min(520px, 100%);
  height: 8px;
  border: 1px solid #555d54;
  border-radius: 999px;
  background: #111411;
}

.mock-slider span {
  display: block;
  width: 28%;
  height: 100%;
  border-radius: inherit;
  background: var(--accent);
}

.phase-strip {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 10px;
  padding: 12px;
  border-top: 1px solid var(--line);
  background: #151915;
}

.phase-strip.six-up {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.viewer-controls {
  display: grid;
  gap: 10px;
  padding: 12px;
  border-top: 1px solid var(--line);
  background: #151915;
}

.button-row.compact {
  margin-top: 0;
  align-items: center;
}

.control-value {
  color: var(--muted);
  font-size: 12px;
}

.slice-row {
  display: grid;
  grid-template-columns: 48px minmax(0, 1fr) 72px;
  gap: 10px;
  align-items: center;
  color: var(--muted);
  font-size: 12px;
}

.slice-row strong {
  color: var(--ink);
  text-align: right;
}

.slice-row input[type="range"] {
  width: 100%;
}

.load-row {
  display: grid;
  grid-template-columns: 210px minmax(0, 1fr);
  gap: 10px;
  align-items: center;
  color: var(--muted);
  font-size: 12px;
}

.progress-track {
  height: 7px;
  overflow: hidden;
  border: 1px solid #555d54;
  border-radius: 999px;
  background: #111411;
}

.progress-track span {
  display: block;
  width: 0;
  height: 100%;
  border-radius: inherit;
  background: var(--accent);
}

.phase-button {
  display: grid;
  grid-template-columns: 76px minmax(0, 1fr);
  gap: 9px;
  align-items: center;
  min-height: 74px;
  padding: 8px;
  border: 1px solid var(--line);
  border-radius: 7px;
  color: var(--ink);
  background: #101410;
  cursor: pointer;
  text-align: left;
}

.phase-button.active {
  border-color: var(--accent);
  background: #0d2926;
}

.phase-button img,
.series-thumb {
  width: 76px;
  height: 56px;
  object-fit: cover;
  background: #000;
}

.series-thumb {
  display: grid;
  place-items: center;
  border: 1px solid var(--line);
  border-radius: 4px;
  color: var(--accent);
  font-weight: 800;
}

.phase-label {
  display: grid;
  gap: 3px;
}

.phase-label strong {
  font-size: 13px;
}

.phase-label span {
  color: var(--muted);
  font-size: 12px;
}

.side-stack {
  display: grid;
  gap: 14px;
  align-content: start;
}

.prompt-list {
  margin: 0;
  padding-left: 18px;
  color: var(--ink);
}

.prompt-list li + li {
  margin-top: 8px;
}

textarea {
  width: 100%;
  min-height: 124px;
  resize: vertical;
  padding: 10px;
  border: 1px solid var(--line);
  border-radius: 6px;
  color: var(--ink);
  background: #0d100d;
}

.button-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 10px;
}

button,
.link-button {
  min-height: 34px;
  padding: 7px 10px;
  border: 1px solid var(--line);
  border-radius: 6px;
  color: var(--ink);
  background: #101410;
  cursor: pointer;
  text-decoration: none;
}

button.primary,
.link-button.primary {
  border-color: rgba(54, 208, 197, 0.7);
  background: #0b302d;
}

.answer-content {
  display: none;
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px solid var(--line);
}

.answer-content.visible {
  display: block;
}

.teaching-point {
  padding: 10px;
  border-left: 3px solid var(--accent-2);
  background: #14120a;
  color: #fff6d8;
}

.source-panel {
  font-size: 12px;
  line-height: 1.45;
  color: var(--muted);
}

.source-panel p {
  margin-bottom: 8px;
}

.source-panel p:last-child {
  margin-bottom: 0;
}

.chapter-list {
  margin: 0;
  padding-left: 18px;
}

.chapter-list li + li {
  margin-top: 8px;
}

@media (max-width: 980px) {
  .intro-grid,
  .chapter-grid,
  .case-layout {
    grid-template-columns: 1fr;
  }

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

  .phase-strip.six-up {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .image-stage {
    min-height: 360px;
  }

  .scan-stage,
  .scan-frame {
    min-height: 460px;
  }

  .load-row {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 620px) {
  .topbar,
  .viewer-head {
    align-items: stretch;
    flex-direction: column;
  }

  .phase-strip {
    grid-template-columns: 1fr;
  }

  .phase-button {
    grid-template-columns: 92px minmax(0, 1fr);
  }

  .phase-button img,
  .series-thumb {
    width: 92px;
  }

  .slice-row {
    grid-template-columns: 44px minmax(0, 1fr) 64px;
  }
}