:root {
  --bg-deep: #050a14;
  --bg: #0a1220;
  --panel: rgba(10, 22, 48, 0.72);
  --panel-solid: #0c1830;
  --panel-elevated: rgba(16, 32, 64, 0.88);
  --glass: rgba(12, 28, 56, 0.55);
  --glass-border: rgba(56, 189, 248, 0.22);
  --accent: #38bdf8;
  --accent-bright: #67e8f9;
  --accent-soft: #0ea5e9;
  --accent-glow: rgba(56, 189, 248, 0.45);
  --accent-dim: rgba(56, 189, 248, 0.12);
  --text: #e8f4ff;
  --text-soft: #b8d4f0;
  --muted: #7a9bb8;
  --border: rgba(56, 120, 180, 0.28);
  --border-bright: rgba(103, 232, 249, 0.35);
  --success: #34d399;
  --warn: #fbbf24;
  --sidebar-width: min(288px, 24vw);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --shadow-panel: 0 8px 32px rgba(0, 0, 0, 0.45), 0 0 0 1px var(--border);
  --font-ui: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-mono: "JetBrains Mono", "Consolas", monospace;
  --stage-base: #0a1424;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

html, body {
  height: 100%;
  font-family: var(--font-ui);
  background: var(--bg-deep);
  color: var(--text);
  overflow: hidden;
}

/* 全屏深空背景 */
.layout-bg {
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background:
    radial-gradient(ellipse 80% 60% at 70% 40%, rgba(14, 116, 178, 0.18) 0%, transparent 55%),
    radial-gradient(ellipse 50% 40% at 15% 80%, rgba(6, 182, 212, 0.1) 0%, transparent 50%),
    linear-gradient(165deg, #050a14 0%, #0a1628 45%, #060d18 100%);
}
.layout-bg::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(56, 189, 248, 0.04) 1px, transparent 1px),
    linear-gradient(90deg, rgba(56, 189, 248, 0.04) 1px, transparent 1px);
  background-size: 48px 48px;
  mask-image: radial-gradient(ellipse 90% 80% at 60% 50%, black 20%, transparent 75%);
}

.layout {
  position: fixed;
  inset: 0;
  z-index: 1;
  display: flex;
  min-width: 0;
  background: var(--stage-base);
}

/* ========== 左侧导航（含外侧折叠钮） ========== */
.topic-nav-column {
  position: relative;
  width: var(--sidebar-width);
  flex-shrink: 0;
  min-height: 0;
  overflow: visible;
  transition: width 0.22s ease;
}

.layout.panel-collapsed .topic-nav-column {
  width: 0;
  min-width: 0;
}

.topic-nav {
  position: relative;
  width: 100%;
  height: 100%;
  min-height: 0;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  background: var(--panel);
  backdrop-filter: blur(16px) saturate(1.2);
  -webkit-backdrop-filter: blur(16px) saturate(1.2);
  border-right: 1px solid var(--border);
  box-shadow: 4px 0 24px rgba(0, 0, 0, 0.35);
  color-scheme: dark;
  transition: opacity 0.18s ease, border-color 0.22s ease;
}

.layout.panel-collapsed .topic-nav {
  border-right-color: transparent;
  opacity: 0;
  pointer-events: none;
}

.topic-nav-body {
  flex: 1;
  min-width: 0;
  min-height: 0;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.topic-nav-toggle-btn {
  position: absolute;
  left: 100%;
  top: 50%;
  z-index: 20;
  transform: translateY(-50%);
  box-sizing: border-box;
  width: 28px;
  height: 52px;
  padding: 0;
  margin: 0;
  font-size: 13px;
  line-height: 1;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  border: 1px solid var(--border-bright);
  border-left: none;
  background: rgba(12, 28, 56, 0.95);
  color: var(--text);
  cursor: pointer;
  font-family: inherit;
  box-shadow: 4px 0 16px rgba(0, 0, 0, 0.35);
  transition: background 0.2s, box-shadow 0.2s, border-color 0.2s, color 0.2s;
}

.topic-nav-toggle-btn:hover {
  background: rgba(56, 189, 248, 0.25);
  border-color: var(--accent);
  color: var(--accent-bright);
  box-shadow: 4px 0 20px rgba(56, 189, 248, 0.2);
}

.topic-nav-toggle-btn:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.layout.panel-collapsed .topic-nav-body {
  display: none;
}

.layout.panel-collapsed .topic-nav-accent {
  opacity: 0.35;
}

.topic-nav-accent {
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: 3px;
  background: linear-gradient(180deg, transparent, var(--accent) 25%, var(--accent-bright) 50%, var(--accent) 75%, transparent);
  box-shadow: 0 0 16px var(--accent-glow), 0 0 4px var(--accent);
  z-index: 2;
  animation: accent-pulse 3s ease-in-out infinite;
}
@keyframes accent-pulse {
  0%, 100% { opacity: 0.85; filter: brightness(1); }
  50% { opacity: 1; filter: brightness(1.15); }
}

.topic-nav-brand {
  flex-shrink: 0;
  position: relative;
  padding: 16px 14px 14px 18px;
  border-bottom: 1px solid var(--border);
  background:
    linear-gradient(135deg, rgba(56, 189, 248, 0.14) 0%, rgba(14, 165, 233, 0.04) 45%, transparent 75%),
    linear-gradient(0deg, rgba(0, 0, 0, 0.15) 0%, transparent 100%);
}
.topic-nav-brand::before {
  content: "";
  position: absolute;
  left: 10px;
  top: 50%;
  transform: translateY(-50%);
  width: 3px;
  height: 62%;
  min-height: 22px;
  border-radius: 2px;
  background: linear-gradient(180deg, var(--accent-bright), var(--accent-soft));
  box-shadow: 0 0 12px var(--accent-glow);
}
.topic-nav-brand-title {
  display: block;
  padding-left: 10px;
  font-size: 1.08rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  line-height: 1.35;
  background: linear-gradient(105deg, #ffffff 0%, var(--accent-bright) 55%, var(--accent) 100%);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  text-shadow: none;
  filter: drop-shadow(0 0 14px rgba(56, 189, 248, 0.35));
}

.topic-nav-section {
  display: flex;
  flex-direction: column;
  min-width: 0;
  min-height: 0;
}
.topic-nav-section--list {
  flex: 3 1 0;
  border-bottom: 1px solid var(--border);
}
.topic-nav-section--controls {
  flex: 0 0 auto;
  border-bottom: 1px solid var(--border);
}
.topic-nav-section--controls[hidden] { display: none !important; }
.topic-nav-controls {
  padding: 8px 12px 10px 14px;
}
.topic-nav-section--explain {
  flex: 2 1 0;
}

.topic-nav-section h2 {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.82rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  color: var(--accent-bright);
  padding: 10px 12px 8px 14px;
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
  text-transform: none;
}

.section-icon {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 8px var(--accent-glow);
  flex-shrink: 0;
}
.section-icon--explain {
  border-radius: 1px;
  width: 6px;
  height: 6px;
  background: transparent;
  border: 1.5px solid var(--accent-bright);
  box-shadow: 0 0 6px var(--accent-glow);
}

.topic-nav-section .topic-nav-scroll {
  flex: 1;
  overflow-y: auto;
  padding: 8px 10px 10px;
  scrollbar-width: thin;
  scrollbar-color: var(--accent-soft) transparent;
}
.topic-nav-scroll::-webkit-scrollbar { width: 5px; }
.topic-nav-scroll::-webkit-scrollbar-thumb {
  background: rgba(56, 189, 248, 0.35);
  border-radius: 4px;
}

.topic-group { margin-bottom: 10px; }
.topic-group h3 {
  font-size: 0.66rem;
  font-weight: 600;
  color: var(--muted);
  letter-spacing: 0.04em;
  margin-bottom: 5px;
  padding-left: 4px;
}

.topic-item {
  display: block;
  width: 100%;
  text-align: left;
  padding: 7px 10px;
  margin-bottom: 4px;
  border: 1px solid transparent;
  border-radius: var(--radius-sm);
  background: rgba(255, 255, 255, 0.03);
  color: var(--text-soft);
  font-size: 0.76rem;
  line-height: 1.35;
  cursor: pointer;
  transition: background 0.2s, border-color 0.2s, box-shadow 0.2s, color 0.2s;
}
.topic-item:hover {
  background: var(--accent-dim);
  border-color: var(--border-bright);
  color: var(--text);
  box-shadow: inset 0 0 0 1px rgba(56, 189, 248, 0.08);
}
.topic-item.active {
  background: linear-gradient(135deg, rgba(14, 165, 233, 0.35) 0%, rgba(56, 189, 248, 0.2) 100%);
  color: #fff;
  border-color: var(--accent-soft);
  box-shadow: 0 0 16px rgba(56, 189, 248, 0.25), inset 0 1px 0 rgba(255, 255, 255, 0.1);
}

.topic-module-select {
  display: block;
  width: 100%;
  padding: 8px 30px 8px 10px;
  margin-bottom: 4px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background-color: var(--panel-solid);
  background-image:
    url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='%2367e8f9' d='M2.5 4.5 6 8l3.5-3.5'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 10px center;
  color: var(--text);
  font-size: 0.76rem;
  font-family: inherit;
  line-height: 1.35;
  cursor: pointer;
  color-scheme: dark;
  -webkit-appearance: none;
  appearance: none;
  transition: border-color 0.2s, box-shadow 0.2s, background-color 0.2s;
}
.topic-module-select:hover {
  border-color: var(--border-bright);
  background-color: rgba(16, 32, 64, 0.95);
  box-shadow: 0 0 12px rgba(56, 189, 248, 0.12);
}
.topic-module-select:focus,
.topic-module-select:focus-visible,
.topic-module-select:active {
  outline: none;
  border-color: var(--accent);
  background-color: rgba(12, 28, 56, 0.98);
  box-shadow: 0 0 0 2px rgba(56, 189, 248, 0.25);
}
.topic-module-select option {
  background-color: #0c1830;
  color: #e8f4ff;
  padding: 8px 10px;
}
.topic-module-select option:checked {
  background: linear-gradient(0deg, rgba(14, 165, 233, 0.45), rgba(14, 165, 233, 0.45)), #0c1830;
  color: #fff;
  font-weight: 600;
}
.topic-module-select option:hover,
.topic-module-select option:focus {
  background-color: #163a5c;
  color: #fff;
}
.topic-module-select option[value=""] {
  color: var(--muted);
}

.topic-demo-panel {
  margin: 0;
  padding: 0;
  border: none;
  background: transparent;
  box-shadow: none;
}
.topic-demo-block[hidden] { display: none !important; }

.auto-rotate-check {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.78rem;
  color: var(--text-soft);
  cursor: pointer;
  user-select: none;
  margin-bottom: 8px;
}

.auto-rotate-check input[type="checkbox"] {
  width: 15px;
  height: 15px;
  accent-color: var(--accent);
  cursor: pointer;
  flex-shrink: 0;
}

.auto-rotate-speed-row {
  display: flex;
  align-items: center;
  gap: 8px;
}

.auto-rotate-speed-row[hidden] { display: none !important; }

.auto-rotate-speed-row input[type="range"] {
  flex: 1;
  min-width: 0;
  margin: 0;
  width: 100%;
  height: 4px;
  accent-color: var(--accent);
  cursor: pointer;
}

.auto-rotate-play-btn {
  flex-shrink: 0;
  width: 30px;
  height: 30px;
  padding: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: rgba(0, 0, 0, 0.25);
  color: var(--text);
  font-size: 13px;
  line-height: 1;
  font-family: inherit;
  cursor: pointer;
  transition: background 0.2s, border-color 0.2s, color 0.2s;
}

.auto-rotate-play-btn:hover:not(:disabled) {
  border-color: var(--border-bright);
  color: var(--accent-bright);
  background: var(--accent-dim);
}

.auto-rotate-play-btn:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.auto-rotate-play-btn:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.view-preset-block {
  margin-top: 10px;
  padding-top: 10px;
  border-top: 1px solid var(--border);
}

.view-preset-label {
  font-size: 0.72rem;
  color: var(--muted);
  margin-bottom: 6px;
  letter-spacing: 0.04em;
}

.view-preset-row {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 6px;
}

.view-preset-btn {
  width: 100%;
  padding: 5px 4px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: rgba(0, 0, 0, 0.22);
  color: var(--text-soft);
  font-size: 0.68rem;
  line-height: 1.25;
  font-family: inherit;
  cursor: pointer;
  transition: background 0.2s, border-color 0.2s, color 0.2s, box-shadow 0.2s;
}

.view-preset-btn:hover {
  border-color: var(--border-bright);
  color: var(--text);
  background: var(--accent-dim);
}

.view-preset-btn.active {
  border-color: var(--accent);
  color: var(--accent-bright);
  background: rgba(56, 189, 248, 0.18);
  box-shadow: 0 0 10px rgba(56, 189, 248, 0.15);
}

.view-preset-btn:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.earth-skin-block {
  margin-top: 10px;
  padding-top: 10px;
  border-top: 1px solid var(--border);
}

.earth-skin-label {
  display: block;
  font-size: 0.72rem;
  color: var(--muted);
  margin-bottom: 6px;
  letter-spacing: 0.04em;
}

.earth-skin-select {
  width: 100%;
}

/* 动画区右下角：参数设置（底边与视图切换栏 bottom: 18px 对齐） */
.stage-params-dock {
  position: absolute;
  right: 14px;
  bottom: 18px;
  z-index: 26;
  width: min(300px, calc(100% - 28px));
  max-width: 320px;
  pointer-events: none;
}
.stage-params-dock[hidden] { display: none !important; }
.stage-params-dock > * { pointer-events: auto; }

.stage-params-panel {
  background: var(--panel-elevated);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--border-bright);
  border-radius: var(--radius-md);
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.45), 0 0 24px rgba(56, 189, 248, 0.1);
  overflow: hidden;
}

.stage-params-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  padding: 8px 10px 8px 12px;
  border-bottom: 1px solid var(--border);
  background: linear-gradient(135deg, rgba(56, 189, 248, 0.12) 0%, transparent 100%);
}

.stage-params-title {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--accent-bright);
  letter-spacing: 0.06em;
  white-space: nowrap;
}

.stage-params-toggle {
  flex-shrink: 0;
  padding: 4px 10px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: rgba(0, 0, 0, 0.25);
  color: var(--text-soft);
  font-size: 0.72rem;
  font-family: inherit;
  cursor: pointer;
  transition: background 0.2s, border-color 0.2s, color 0.2s;
}
.stage-params-toggle:hover {
  border-color: var(--border-bright);
  color: var(--text);
  background: var(--accent-dim);
}

.stage-params-body {
  max-height: min(42vh, 380px);
  overflow-y: auto;
  overflow-x: hidden;
  padding: 8px 10px 10px;
  scrollbar-width: thin;
  scrollbar-color: var(--accent-soft) transparent;
}
.stage-params-body[hidden] { display: none !important; }

.stage-params-body .topic-demo-panel input[type="range"] {
  width: 100%;
}

.stage-wrap.flat .stage-params-dock {
  bottom: 18px;
}

@media (max-width: 720px) {
  .stage-params-dock {
    right: 10px;
    left: auto;
    width: auto;
    max-width: none;
    bottom: 18px;
  }
  .stage-wrap.flat .stage-params-dock {
    bottom: 18px;
  }
}

.topic-demo-row-label {
  font-size: 0.68rem;
  color: var(--muted);
  margin-bottom: 6px;
  line-height: 1.4;
  word-break: break-word;
}
.topic-demo-row-label--hint {
  color: var(--muted);
  opacity: 0.9;
}

.topic-demo-panel input[type="range"] {
  width: 100%;
  height: 4px;
  margin: 4px 0;
  -webkit-appearance: none;
  appearance: none;
  background: rgba(56, 189, 248, 0.15);
  border-radius: 2px;
  outline: none;
}
.stage-params-body input[type="range"]::-webkit-slider-thumb,
.topic-demo-panel input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: linear-gradient(145deg, var(--accent-bright), var(--accent-soft));
  border: 2px solid rgba(255, 255, 255, 0.9);
  box-shadow: 0 0 10px var(--accent-glow);
  cursor: pointer;
}
.stage-params-body input[type="range"]::-moz-range-thumb,
.topic-demo-panel input[type="range"]::-moz-range-thumb {
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: linear-gradient(145deg, var(--accent-bright), var(--accent-soft));
  border: 2px solid rgba(255, 255, 255, 0.9);
  box-shadow: 0 0 10px var(--accent-glow);
  cursor: pointer;
}

.topic-demo-value {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  font-weight: 600;
  text-align: center;
  margin-top: 6px;
  color: var(--accent-bright);
  text-shadow: 0 0 12px var(--accent-glow);
  font-variant-numeric: tabular-nums;
}

/* 知识解读卡片 */
.topic-nav-section--explain .explain-side-card {
  flex: 1;
  min-height: 0;
  margin: 0 8px 8px;
  display: flex;
  flex-direction: column;
  background: var(--glass);
  backdrop-filter: blur(8px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-md);
  padding: 10px 12px;
  box-shadow: var(--shadow-panel);
}
.explain-side-scroll {
  flex: 1;
  min-height: 0;
  overflow-y: auto;
  overflow-x: hidden;
  -webkit-overflow-scrolling: touch;
  margin-top: 6px;
  scrollbar-width: thin;
  scrollbar-color: var(--accent-soft) transparent;
}
.explain-side-card .step-title {
  font-weight: 600;
  font-size: 0.86rem;
  margin-bottom: 4px;
  line-height: 1.45;
  color: var(--text);
}
.explain-side-card .explain {
  font-size: 0.8rem;
  line-height: 1.7;
  color: var(--text-soft);
}
.explain-side-card .progress-row {
  margin-top: 10px;
  padding-top: 8px;
  border-top: 1px dashed var(--border);
  font-size: 0.74rem;
  color: var(--muted);
  line-height: 1.45;
}

.module-tag {
  display: none;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  padding: 3px 10px;
  border-radius: 4px;
  background: var(--accent-dim);
  color: var(--accent-bright);
  border: 1px solid var(--border-bright);
  margin-bottom: 8px;
  letter-spacing: 0.04em;
}

.topic-nav-copyright-entry {
  flex-shrink: 0;
  padding: 8px 10px 10px;
  border-top: 1px solid var(--border);
  background: linear-gradient(0deg, rgba(0, 0, 0, 0.2) 0%, transparent 100%);
}
.copyright-text-btn {
  display: block;
  width: 100%;
  padding: 7px 10px;
  font-size: 0.72rem;
  cursor: pointer;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: rgba(0, 0, 0, 0.2);
  color: var(--muted);
  transition: background 0.2s, border-color 0.2s, color 0.2s, box-shadow 0.2s;
}
.copyright-text-btn:hover {
  background: var(--accent-dim);
  border-color: var(--border-bright);
  color: var(--text-soft);
  box-shadow: 0 0 12px rgba(56, 189, 248, 0.1);
}
.copyright-text-btn:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

/* ========== 画布舞台 ========== */
.stage-wrap {
  flex: 1 1 auto;
  position: relative;
  min-width: 0;
  min-height: 0;
  background: var(--stage-base);
  overflow: hidden;
}

.stage-backdrop {
  position: absolute;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background:
    radial-gradient(ellipse 70% 55% at 50% 45%, rgba(14, 116, 178, 0.12) 0%, transparent 60%),
    radial-gradient(circle at 50% 50%, rgba(6, 78, 120, 0.08) 0%, transparent 45%);
}
.stage-backdrop::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(56, 189, 248, 0.06) 1px, transparent 1px),
    linear-gradient(90deg, rgba(56, 189, 248, 0.06) 1px, transparent 1px);
  background-size: 56px 56px;
  opacity: 0.7;
  mask-image: radial-gradient(ellipse 85% 75% at 50% 50%, black 15%, transparent 70%);
}
.stage-backdrop::after {
  content: "";
  position: absolute;
  inset: 0;
  background: radial-gradient(ellipse 100% 100% at 50% 50%, transparent 40%, rgba(5, 10, 20, 0.65) 100%);
}

#canvas3d,
#canvas2d {
  position: absolute;
  inset: 0;
  z-index: 1;
  display: block;
  width: 100%;
  height: 100%;
  max-width: none;
  max-height: none;
}
#canvas3d {
  cursor: grab;
  touch-action: none;
  background: var(--stage-base);
}
#canvas3d:active { cursor: grabbing; }
#canvas2d {
  display: none;
  background: var(--stage-base);
  touch-action: none;
}
.stage-wrap.flat #canvas3d { display: none; }
.stage-wrap.flat #canvas2d { display: block; }

.hint-3d,
.hint-2d,
.hint-flat-title {
  position: absolute;
  z-index: 8;
  font-family: var(--font-ui);
  font-size: 0.74rem;
  font-weight: 400;
  line-height: 1.4;
  color: var(--text-soft);
  background: var(--glass);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  padding: 7px 12px;
  border-radius: var(--radius-sm);
  pointer-events: none;
  border: 1px solid var(--glass-border);
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.3);
}
.hint-3d {
  top: 14px;
  left: 14px;
  max-width: min(380px, calc(100% - 28px));
  text-align: left;
}
.stage-wrap.flat .hint-3d { display: none; }
.hint-flat-title {
  display: none;
  top: 14px;
  left: 14px;
  max-width: min(420px, calc(100% - 28px));
  text-align: left;
}
.stage-wrap.flat .hint-flat-title { display: block; }
.hint-2d {
  display: none;
  bottom: 76px;
  right: 16px;
  max-width: min(320px, 90vw);
}
.stage-wrap.flat .hint-2d { display: block; }

.teaching-angle-label {
  position: absolute;
  z-index: 40;
  left: 50%;
  bottom: 108px;
  transform: translateX(-50%);
  max-width: min(560px, calc(100% - 24px));
  padding: 12px 22px;
  font-size: 0.95rem;
  font-weight: 600;
  line-height: 1.45;
  text-align: center;
  color: var(--text);
  background: var(--panel-elevated);
  backdrop-filter: blur(12px);
  border: 1px solid var(--border-bright);
  border-radius: var(--radius-lg);
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.4), 0 0 24px rgba(56, 189, 248, 0.12);
  pointer-events: none;
}
.teaching-angle-label[hidden] { display: none !important; }
.teaching-angle-label .teaching-angle-val {
  font-family: var(--font-mono);
  font-size: 1.42rem;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  color: var(--accent-bright);
  text-shadow: 0 0 16px var(--accent-glow);
}
.teaching-angle-label .teaching-angle-name {
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--text-soft);
}

.stage-reset-wrap {
  position: absolute;
  top: 14px;
  right: 14px;
  z-index: 28;
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
  justify-content: flex-end;
  max-width: calc(100% - 28px);
}
.stage-reset-wrap button {
  padding: 9px 16px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--glass);
  backdrop-filter: blur(8px);
  color: var(--text-soft);
  cursor: pointer;
  font-size: 0.86rem;
  font-family: inherit;
  transition: background 0.2s, border-color 0.2s, color 0.2s, box-shadow 0.2s;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.25);
}
.stage-reset-wrap button:hover {
  background: var(--accent-dim);
  border-color: var(--border-bright);
  color: var(--text);
  box-shadow: 0 0 16px rgba(56, 189, 248, 0.15);
}
.stage-reset-wrap button.primary {
  background: linear-gradient(135deg, var(--accent-soft), #0284c7);
  color: #fff;
  border-color: var(--accent);
}
.stage-reset-wrap button.hidden { display: none !important; }

/* 视图切换 */
.stage-view-tabs {
  position: absolute;
  left: 50%;
  bottom: 18px;
  transform: translateX(-50%);
  z-index: 30;
  display: flex;
  justify-content: center;
  pointer-events: none;
}
.stage-view-tabs > .view-tabs {
  pointer-events: auto;
  background: var(--panel-elevated);
  backdrop-filter: blur(12px);
  border: 1px solid var(--border-bright);
  box-shadow: 0 8px 28px rgba(0, 0, 0, 0.45), 0 0 20px rgba(56, 189, 248, 0.1);
}
.view-tabs {
  display: flex;
  border-radius: var(--radius-md);
  overflow: hidden;
  padding: 3px;
  gap: 2px;
}
.view-tabs button {
  padding: 9px 20px;
  border: none;
  border-radius: 7px;
  background: transparent;
  color: var(--muted);
  cursor: pointer;
  font-size: 0.86rem;
  font-family: inherit;
  transition: background 0.2s, color 0.2s, box-shadow 0.2s;
}
.view-tabs button:hover {
  color: var(--text-soft);
  background: rgba(255, 255, 255, 0.05);
}
.view-tabs button.active {
  background: linear-gradient(135deg, rgba(14, 165, 233, 0.5), rgba(56, 189, 248, 0.35));
  color: #fff;
  box-shadow: 0 0 14px rgba(56, 189, 248, 0.3);
}

/* 版权弹窗 */
.copyright-modal-overlay {
  position: fixed;
  inset: 0;
  z-index: 10050;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px;
  background: rgba(2, 6, 16, 0.75);
  backdrop-filter: blur(6px);
}
.copyright-modal-overlay[hidden] { display: none !important; }

.copyright-modal-dialog {
  width: min(96vw, 520px);
  max-height: min(92vh, 720px);
  overflow-y: auto;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-bright);
  background: linear-gradient(165deg, #0f1f3d 0%, #060d1f 55%, #040810 100%);
  padding: 20px;
  box-shadow: 0 24px 56px rgba(0, 0, 0, 0.6), 0 0 40px rgba(56, 189, 248, 0.08);
}
.copyright-modal-title {
  margin: 0 0 14px;
  font-size: 1.1rem;
  color: var(--text);
  text-align: center;
  letter-spacing: 0.06em;
}
.copyright-modal-qr-row {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 24px 30px;
  align-items: flex-start;
}
.copyright-modal-qr-col { text-align: center; flex-shrink: 0; }
.copyright-qrcode {
  display: block;
  margin: 0 auto;
  max-width: 150px;
  width: 100%;
  height: auto;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-bright);
  box-shadow: 0 0 20px rgba(56, 189, 248, 0.15);
}
.copyright-modal-qr-caption {
  margin: 8px 0 0;
  font-size: 0.88rem;
  color: var(--text-soft);
  line-height: 1.4;
}
.copyright-note {
  margin: 14px 0 0;
  font-size: 0.82rem;
  color: var(--muted);
  line-height: 1.65;
  text-align: center;
}
.copyright-modal-actions {
  margin-top: 14px;
  display: flex;
  justify-content: center;
}
.copyright-modal-actions button {
  min-width: 120px;
  padding: 9px 18px;
  font-size: 0.9rem;
  cursor: pointer;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-bright);
  background: var(--accent-dim);
  color: var(--text);
  font-family: inherit;
  transition: background 0.2s, box-shadow 0.2s;
}
.copyright-modal-actions button:hover {
  background: rgba(56, 189, 248, 0.25);
  box-shadow: 0 0 16px rgba(56, 189, 248, 0.2);
}

@media (max-width: 1100px) {
  :root { --sidebar-width: min(272px, 30vw); }
}
@media (max-width: 720px) {
  .topic-nav-column { width: min(100%, 100vw); }
  .layout.panel-collapsed .topic-nav-column {
    width: 0;
    min-width: 0;
  }
  .layout.panel-collapsed .topic-nav {
    opacity: 0;
  }
  .topic-nav-toggle-btn {
    left: auto;
    right: 12px;
    top: auto;
    bottom: 12px;
    transform: none;
    border-radius: var(--radius-sm);
    border-left: 1px solid var(--border-bright);
    width: 36px;
    height: 36px;
  }
  .topic-nav-section--list {
    flex: 1 1 42vh;
    max-height: 48vh;
  }
  .topic-nav-section--explain {
    flex: 1 1 30vh;
    min-height: 160px;
  }
  .topic-nav-brand { padding: 14px 12px 12px 16px; }
  .topic-nav-brand-title { font-size: 0.98rem; letter-spacing: 0.08em; }
}

@media (prefers-reduced-motion: reduce) {
  .topic-nav-accent { animation: none; }
  .topic-nav-column { transition: none; }
  .topic-nav { transition: none; }
}