/* ===== 全局重置 ===== */
*, *::before, *::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --bg-primary: #0a0a0f;
  --bg-secondary: #12121a;
  --bg-card: #1a1a28;
  --text-primary: #e8e8e8;
  --text-secondary: #9999aa;
  --text-muted: #555566;
  --accent: #ffd700;
  --accent-glow: rgba(255, 215, 0, 0.15);
  --accent-dim: #b8960a;
  --border: #2a2a3a;
  --border-glow: rgba(255, 215, 0, 0.3);
  --font-serif: 'Noto Serif SC', 'Source Han Serif SC', 'Songti SC', serif;
  --font-mono: 'JetBrains Mono', 'Consolas', monospace;
  --transition-slow: 800ms ease;
  --transition-normal: 400ms ease;
  --transition-fast: 200ms ease;
}

html, body {
  height: 100%;
  background: var(--bg-primary);
  color: var(--text-primary);
  font-family: var(--font-serif);
  font-size: 17px;
  line-height: 1.8;
  overflow-y: auto;
  overflow-x: hidden;
}

.hidden { display: none !important; }

/* ===== 通用屏幕 ===== */
.screen {
  position: fixed;
  top: 0; left: 0; right: 0; bottom: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  transition: opacity var(--transition-slow);
  overflow-y: auto;
}

.screen.hidden {
  opacity: 0;
  pointer-events: none;
}

/* ===== 标题画面 ===== */
#title-screen {
  background: radial-gradient(ellipse at center, #0a0a1a 0%, #050508 100%);
  justify-content: center;
  min-height: 100vh;
}

.title-content {
  text-align: center;
  animation: fadeInUp 1.5s ease forwards;
}

.title-main {
  font-family: var(--font-serif);
  font-size: 3.5rem;
  font-weight: 700;
  letter-spacing: 0.3em;
  color: var(--accent);
  text-shadow: 0 0 40px var(--accent-glow), 0 0 80px var(--accent-glow);
  margin-bottom: 0.5rem;
}

.title-sub {
  font-size: 1.1rem;
  color: var(--text-secondary);
  letter-spacing: 0.15em;
  margin-bottom: 1rem;
}

.title-decoration {
  color: var(--text-muted);
  letter-spacing: 0.5em;
  margin-bottom: 3rem;
  font-size: 0.9rem;
}

/* ===== 按钮 ===== */
.btn-primary {
  display: inline-block;
  background: transparent;
  color: var(--accent);
  border: 1px solid var(--accent);
  padding: 12px 40px;
  font-family: var(--font-serif);
  font-size: 1.05rem;
  letter-spacing: 0.15em;
  cursor: pointer;
  transition: all var(--transition-fast);
  margin: 8px;
}

.btn-primary:hover {
  background: var(--accent-glow);
  box-shadow: 0 0 20px var(--accent-glow), inset 0 0 20px var(--accent-glow);
}

.btn-secondary {
  display: inline-block;
  background: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--border);
  padding: 10px 30px;
  font-family: var(--font-serif);
  font-size: 0.95rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  margin: 6px;
}

.btn-secondary:hover {
  color: var(--text-primary);
  border-color: var(--text-secondary);
}

.btn-back {
  background: transparent;
  color: var(--text-muted);
  border: none;
  font-family: var(--font-serif);
  font-size: 0.9rem;
  cursor: pointer;
  position: fixed;
  bottom: 30px;
  left: 30px;
  transition: color var(--transition-fast);
}

.btn-back:hover {
  color: var(--text-primary);
}

/* ===== 章节选择 ===== */
#chapter-select-screen {
  justify-content: flex-start;
  padding-top: 80px;
  background: var(--bg-primary);
}

.screen-title {
  font-size: 1.5rem;
  letter-spacing: 0.3em;
  color: var(--accent);
  margin-bottom: 40px;
  font-weight: 400;
}

#chapter-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
  width: 100%;
  max-width: 500px;
  padding: 0 20px;
}

.chapter-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 24px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  cursor: pointer;
  transition: all var(--transition-fast);
  text-align: left;
  font-family: var(--font-serif);
}

.chapter-item:hover {
  border-color: var(--accent);
  background: var(--accent-glow);
}

.chapter-item.completed {
  border-color: var(--accent-dim);
}

.chapter-item.locked {
  opacity: 0.4;
  cursor: not-allowed;
}

.chapter-num {
  color: var(--accent-dim);
  font-size: 0.8rem;
  font-family: var(--font-mono);
  margin-right: 16px;
}

.chapter-title {
  flex: 1;
  color: var(--text-primary);
  font-size: 1rem;
}

.chapter-status {
  font-size: 0.8rem;
  color: var(--text-muted);
  font-family: var(--font-mono);
}

.chapter-item.completed .chapter-status {
  color: var(--accent-dim);
}

/* ===== 游戏画面 ===== */
#game-screen {
  justify-content: flex-start;
  padding: 0;
}

#top-bar {
  position: fixed;
  top: 0; left: 0; right: 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 20px;
  background: rgba(10, 10, 15, 0.95);
  border-bottom: 1px solid var(--border);
  z-index: 10;
  height: 50px;
}

.top-btn {
  background: transparent;
  color: var(--text-muted);
  border: none;
  font-size: 1.1rem;
  cursor: pointer;
  padding: 4px 8px;
  transition: color var(--transition-fast);
}

.top-btn:hover {
  color: var(--text-primary);
}

#chapter-label {
  font-size: 0.85rem;
  color: var(--accent-dim);
  font-family: var(--font-mono);
  letter-spacing: 0.1em;
}

#scene-container {
  position: fixed;
  top: 50px;
  left: 0; right: 0;
  bottom: 50px;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 40px 20px;
}

#scene-content {
  width: 100%;
  max-width: 680px;
}

/* ===== 叙事文本 ===== */
.narrative-text {
  margin-bottom: 1.5rem;
  opacity: 0;
  animation: fadeIn 0.6s ease forwards;
}

.narrative-text .para {
  margin-bottom: 1.2rem;
  opacity: 0;
}

.narrative-text .typing {
  overflow: hidden;
  white-space: pre-wrap;
}

/* ===== 场景标题 ===== */
.scene-title {
  text-align: center;
  color: var(--accent);
  font-size: 1.3rem;
  letter-spacing: 0.2em;
  margin-bottom: 2rem;
  font-weight: 400;
}

.scene-subtitle {
  text-align: center;
  color: var(--text-muted);
  font-size: 0.9rem;
  margin-bottom: 2.5rem;
  font-family: var(--font-mono);
}

/* ===== 分隔线 ===== */
.scene-divider {
  text-align: center;
  color: var(--text-muted);
  letter-spacing: 0.5em;
  margin: 2rem 0;
  font-size: 0.8rem;
}

/* ===== 选择按钮 ===== */
#choices-container {
  width: 100%;
  max-width: 680px;
  margin-top: 1rem;
}

.choice-btn {
  display: block;
  width: 100%;
  background: transparent;
  color: var(--text-primary);
  border: 1px solid var(--border);
  padding: 14px 20px;
  margin-bottom: 10px;
  font-family: var(--font-serif);
  font-size: 0.95rem;
  text-align: left;
  cursor: pointer;
  transition: all var(--transition-fast);
  position: relative;
  opacity: 0;
  animation: fadeInUp 0.4s ease forwards;
}

.choice-btn:hover {
  border-color: var(--accent);
  background: var(--accent-glow);
  color: var(--accent);
  padding-left: 28px;
}

.choice-btn.locked {
  opacity: 0.3;
  cursor: not-allowed;
}

.choice-btn.locked::after {
  content: ' 🔒';
  color: var(--text-muted);
  font-size: 0.8rem;
}

.choice-btn.locked:hover {
  border-color: var(--border);
  background: transparent;
  color: var(--text-primary);
  padding-left: 20px;
}

.choice-arrow {
  color: var(--accent-dim);
  margin-right: 10px;
  font-family: var(--font-mono);
}

/* ===== 底部状态栏 ===== */
#bottom-bar {
  position: fixed;
  bottom: 0; left: 0; right: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 16px;
  padding: 10px 20px;
  background: rgba(10, 10, 15, 0.95);
  border-top: 1px solid var(--border);
  z-index: 10;
  height: 50px;
}

#typewriter-indicator {
  font-size: 0.75rem;
  color: var(--text-muted);
  font-family: var(--font-mono);
}

.bottom-btn {
  background: transparent;
  color: var(--text-muted);
  border: 1px solid transparent;
  padding: 4px 12px;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.bottom-btn:hover {
  color: var(--text-primary);
  border-color: var(--border);
}

.bottom-btn.active {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-glow);
}

/* ===== KaTeX 公式样式 ===== */
.narrative-text .katex { font-size: 1.1em; overflow-x: auto; overflow-y: hidden; max-width: 100%; }
.narrative-text .katex .katex-html { overflow-x: auto; overflow-y: hidden; max-width: 100%; }
.narrative-text .katex-display {
  margin: 1.2rem 0;
  overflow-x: auto;
  overflow-y: hidden;
  padding: 8px 0;
  max-width: 100%;
}
.formula-error { color: #ff6b6b; font-style: italic; }
.paper-link {
  color: var(--accent);
  text-decoration: underline;
  text-decoration-style: dotted;
  cursor: pointer;
  transition: color var(--transition-fast);
}
.paper-link:hover { color: #fff; }

/* ===== 论文引用弹窗 ===== */
.paper-panel {
  position: relative;
  background: var(--bg-secondary);
  border: 1px solid var(--accent-dim);
  max-width: 600px;
  width: 90%;
  padding: 32px;
  max-height: 80vh;
  overflow-y: auto;
  animation: fadeInUp 0.3s ease forwards;
}
.paper-panel h3 {
  color: var(--accent);
  font-size: 1.2rem;
  font-weight: 400;
  letter-spacing: 0.05em;
  margin-bottom: 8px;
}
.paper-authors, .paper-year {
  color: var(--text-muted);
  font-size: 0.85rem;
  font-family: var(--font-mono);
  margin-bottom: 4px;
}
.paper-abstract {
  color: var(--text-primary);
  font-size: 0.9rem;
  line-height: 1.8;
  margin: 16px 0;
  padding: 16px;
  background: var(--bg-card);
  border-left: 2px solid var(--accent-dim);
}
.paper-actions {
  display: flex;
  gap: 10px;
  margin-top: 16px;
}
.paper-actions .btn-secondary { flex: 1; text-align: center; }

/* ===== 物理图示 SVG ===== */
.diagram-container {
  width: 100%;
  max-width: 620px;
  margin: 1.2rem auto;
  padding: 12px;
  background: rgba(255,255,255,0.03);
  border: 1px solid rgba(255,215,0,0.15);
  border-radius: 4px;
}
.diagram-svg {
  width: 100%;
  height: auto;
  display: block;
}
.diagram-curve, .diagram-curve-wrong {
  stroke-linecap: round;
  stroke-linejoin: round;
}
.diagram-caption {
  text-align: center;
  color: var(--text-muted);
  font-size: 0.75rem;
  margin-top: 8px;
  line-height: 1.5;
  font-family: var(--font-mono);
}
.diagram-caption .katex { font-size: 1em; }
.diagram-block {
  margin: 0.8rem 0;
}
.diagram-error {
  color: #ff6b6b;
  font-style: italic;
  text-align: center;
  padding: 20px;
  border: 1px dashed #ff6b6b;
  margin: 1rem 0;
}
.diagram-svg text {
  user-select: none;
}

/* ===== 知识卡片 ===== */
.overlay {
  position: fixed;
  top: 0; left: 0; right: 0; bottom: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 100;
  transition: opacity var(--transition-normal);
}

.overlay.hidden {
  opacity: 0;
  pointer-events: none;
}

.overlay-bg {
  position: absolute;
  top: 0; left: 0; right: 0; bottom: 0;
  background: rgba(0, 0, 0, 0.7);
}

.knowledge-card {
  position: relative;
  background: var(--bg-card);
  border: 1px solid var(--accent);
  max-width: 500px;
  width: 90%;
  padding: 32px;
  max-height: 85vh;
  overflow-y: auto;
  animation: fadeInUp 0.4s ease forwards;
}

.knowledge-header {
  margin-bottom: 12px;
}

.knowledge-badge {
  color: var(--accent);
  font-size: 0.75rem;
  letter-spacing: 0.15em;
  font-family: var(--font-mono);
}

.knowledge-card h3 {
  color: var(--accent);
  font-size: 1.3rem;
  font-weight: 400;
  margin-bottom: 16px;
  letter-spacing: 0.1em;
}

.knowledge-card p {
  color: var(--text-primary);
  line-height: 1.8;
  font-size: 0.95rem;
  margin-bottom: 12px;
}

.knowledge-card .formula {
  text-align: center;
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: 1.1rem;
  padding: 16px;
  border: 1px dashed var(--accent-dim);
  margin: 16px 0;
}

.knowledge-card .btn-primary {
  margin-top: 12px;
  width: 100%;
}

/* ===== 存档面板 ===== */
.save-panel {
  position: relative;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  padding: 24px;
  max-width: 400px;
  width: 90%;
}

.save-panel h3 {
  text-align: center;
  color: var(--accent);
  letter-spacing: 0.15em;
  margin-bottom: 20px;
  font-weight: 400;
}

.save-slot {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 14px;
  margin-bottom: 8px;
  border: 1px solid var(--border);
  cursor: pointer;
  transition: all var(--transition-fast);
  background: var(--bg-card);
}

.save-slot:hover {
  border-color: var(--accent);
}

.save-slot-info {
  flex: 1;
}

.save-slot-name {
  font-size: 0.85rem;
  color: var(--text-primary);
  margin-bottom: 2px;
}

.save-slot-date {
  font-size: 0.75rem;
  color: var(--text-muted);
  font-family: var(--font-mono);
}

.save-slot-empty {
  color: var(--text-muted);
  font-size: 0.85rem;
}

.save-slot-actions {
  display: flex;
  gap: 6px;
}

.save-slot-btn {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text-secondary);
  padding: 4px 10px;
  font-size: 0.75rem;
  cursor: pointer;
  font-family: var(--font-mono);
  transition: all var(--transition-fast);
}

.save-slot-btn:hover {
  border-color: var(--accent);
  color: var(--accent);
}

#btn-save-close {
  width: 100%;
  margin-top: 12px;
}

/* ===== 章节结束画面 ===== */
#ending-screen {
  background: var(--bg-primary);
  padding: 60px 20px;
}

#ending-content {
  text-align: center;
  max-width: 600px;
}

.ending-title {
  font-size: 2rem;
  color: var(--accent);
  margin-bottom: 1rem;
  text-shadow: 0 0 30px var(--accent-glow);
}

.ending-text {
  color: var(--text-primary);
  margin-bottom: 1.5rem;
}

.ending-knowledge-summary {
  margin: 2rem 0;
  padding: 20px;
  border: 1px dashed var(--accent-dim);
}

.ending-knowledge-summary h4 {
  color: var(--accent);
  letter-spacing: 0.1em;
  margin-bottom: 10px;
  font-weight: 400;
}

.ending-knowledge-summary ul {
  list-style: none;
}

.ending-knowledge-summary li {
  color: var(--text-secondary);
  font-size: 0.9rem;
  margin-bottom: 4px;
}

.ending-knowledge-summary li::before {
  content: '⚬ ';
  color: var(--accent-dim);
}

/* ===== 选择题场景 ===== */
.quiz-question {
  color: var(--accent);
  font-size: 1rem;
  margin-bottom: 1.5rem;
  padding: 16px;
  border-left: 2px solid var(--accent);
  background: var(--accent-glow);
}

.quiz-feedback {
  padding: 14px;
  margin-top: 12px;
  text-align: center;
  animation: fadeIn 0.3s ease forwards;
}

.quiz-feedback.correct {
  color: #4aff8b;
  border: 1px solid #4aff8b;
  background: rgba(74, 255, 139, 0.08);
}

.quiz-feedback.wrong {
  color: #ff6b6b;
  border: 1px solid #ff6b6b;
  background: rgba(255, 107, 107, 0.08);
}

/* ===== 动画 ===== */
@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(15px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ===== 滚动条 ===== */
#scene-container::-webkit-scrollbar {
  width: 4px;
}

#scene-container::-webkit-scrollbar-track {
  background: transparent;
}

#scene-container::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 2px;
}

/* ===== 响应式 ===== */
@media (max-width: 600px) {
  html, body { font-size: 15px; }

  .title-main { font-size: 2.2rem; }

  .title-sub { font-size: 0.9rem; }

  #scene-container { padding: 20px 16px; }

  .knowledge-card {
    padding: 20px;
    max-height: 88vh;
    width: 94%;
  }

  .paper-panel {
    padding: 20px;
    max-height: 85vh;
    width: 94%;
  }
}