/* ========== 主题系统 ========== */
:root {
  --bg: #FFFFFF;
  --bg-secondary: #F5F5F5;
  --bg-tertiary: #EBEBEB;
  --border: #E0E0E0;
  --text: #1A1A1A;
  --text-secondary: #6B7280;
  --accent: #4F46E5;
  --accent-hover: #4338CA;
  --accent-glow: #6366f1;
  --ai-primary: #9333EA;
  --ai-secondary: #DB2777;
  --success: #059669;

  --bubble-user: var(--accent);
  --bubble-ai: var(--bg-secondary);
  --shadow-card: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
  --shadow-card-hover: 0 4px 12px rgba(0,0,0,0.08);

  color-scheme: light;
}

[data-theme="dark"] {
  --bg: #0D0D0D;
  --bg-secondary: #1A1A1A;
  --bg-tertiary: #262626;
  --border: #333333;
  --text: #E5E5E5;
  --text-secondary: #A3A3A3;
  --accent: #5E6AD2;
  --accent-hover: #7C85E0;
  --accent-glow: #818cf8;
  --ai-primary: #a855f7;
  --ai-secondary: #ec4899;
  --success: #10b981;

  --bubble-user: var(--accent);
  --bubble-ai: var(--bg-tertiary);
  --shadow-card: 0 1px 3px rgba(0,0,0,0.3), 0 1px 2px rgba(0,0,0,0.2);
  --shadow-card-hover: 0 4px 16px rgba(0,0,0,0.4);

  color-scheme: dark;
}

/* ========== Reset & Base ========== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  overflow-x: hidden;
  transition: background 0.3s, color 0.3s;
}

/* ========== 背景光效 ========== */
.ambient-glow {
  position: fixed;
  top: -200px;
  left: 50%;
  transform: translateX(-50%);
  width: 800px;
  height: 500px;
  background: radial-gradient(ellipse, var(--accent-glow) 0%, transparent 70%);
  opacity: 0.06;
  border-radius: 50%;
  filter: blur(80px);
  pointer-events: none;
  z-index: 0;
}

[data-theme="dark"] .ambient-glow { opacity: 0.08; }

/* ========== Header ========== */
.header {
  position: relative;
  z-index: 10;
  max-width: 960px;
  margin: 0 auto;
  padding: 24px 24px 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
}

.header-title {
  font-size: 15px;
  font-weight: 600;
  color: var(--text);
  letter-spacing: -0.01em;
}

.theme-toggle {
  width: 36px;
  height: 36px;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: var(--bg-secondary);
  color: var(--text-secondary);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.3s;
}

.theme-toggle:hover {
  background: var(--bg-tertiary);
  color: var(--text);
}

.theme-toggle svg { width: 18px; height: 18px; }

/* ========== Hero ========== */
.hero {
  position: relative;
  z-index: 10;
  max-width: 960px;
  margin: 0 auto;
  padding: 48px 24px 32px;
  text-align: center;
}

.hero h1 {
  font-size: 28px;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 12px;
  color: var(--text);
}

.hero h1 .gradient-text {
  background: linear-gradient(135deg, var(--ai-primary), var(--ai-secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero p {
  font-size: 15px;
  color: var(--text-secondary);
  max-width: 520px;
  margin: 0 auto;
}

/* ========== Tab 导航 ========== */
.tab-nav {
  display: inline-flex;
  align-items: center;
  padding: 4px;
  background: var(--bg-secondary);
  border-radius: 9999px;
  border: 1px solid var(--border);
  gap: 2px;
}

.tab-btn {
  padding: 8px 24px;
  border-radius: 9999px;
  font-size: 13px;
  font-weight: 500;
  border: none;
  cursor: pointer;
  transition: all 0.3s;
  background: transparent;
  color: var(--text-secondary);
  white-space: nowrap;
}

.tab-btn.active {
  background: var(--bg);
  color: var(--text);
  box-shadow: var(--shadow-card);
}

.tab-btn:not(.active):hover {
  color: var(--text);
}

/* ========== Demo 区 ========== */
.demo-section {
  position: relative;
  z-index: 10;
  max-width: 960px;
  margin: 0 auto;
  padding: 0 24px 40px;
  width: 100%;
}

.demo-header {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 16px;
  margin-bottom: 24px;
}

.demo-container {
  background: var(--bg-secondary);
  border-radius: 20px;
  border: 1px solid var(--border);
  overflow: hidden;
  min-height: 420px;
  display: flex;
  flex-direction: column;
}

.demo-toolbar {
  padding: 14px 20px;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: var(--bg);
}

.demo-toolbar-title {
  font-size: 13px;
  font-weight: 600;
  color: var(--text);
  display: flex;
  align-items: center;
  gap: 8px;
}

.demo-toolbar-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--success);
  animation: pulse-dot 2s infinite;
}

@keyframes pulse-dot {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.4; }
}

.demo-start-btn {
  padding: 6px 16px;
  border-radius: 9999px;
  font-size: 12px;
  font-weight: 500;
  border: none;
  cursor: pointer;
  background: var(--accent);
  color: #fff;
  transition: all 0.3s;
}

.demo-start-btn:hover { background: var(--accent-hover); }
.demo-start-btn:disabled { opacity: 0.5; cursor: not-allowed; }

.demo-chat {
  flex: 1;
  padding: 20px;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

/* ========== 聊天气泡 ========== */
.msg {
  display: flex;
  gap: 10px;
  max-width: 85%;
  animation: fadeInUp 0.4s ease-out;
}

.msg.user { align-self: flex-end; flex-direction: row-reverse; }
.msg.ai { align-self: flex-start; }

.msg-avatar {
  width: 32px;
  height: 32px;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
  flex-shrink: 0;
}

.msg.user .msg-avatar {
  background: var(--accent);
  color: #fff;
}

.msg.ai .msg-avatar {
  background: linear-gradient(135deg, var(--ai-primary), var(--ai-secondary));
  color: #fff;
}

.msg-bubble {
  padding: 12px 16px;
  border-radius: 16px;
  font-size: 14px;
  line-height: 1.7;
  position: relative;
}

.msg.user .msg-bubble {
  background: var(--accent);
  color: #fff;
  border-bottom-right-radius: 4px;
}

.msg.ai .msg-bubble {
  background: var(--bubble-ai);
  color: var(--text);
  border-bottom-left-radius: 4px;
  border: 1px solid var(--border);
}

/* 打字光标 */
.typing-cursor {
  display: inline-block;
  width: 2px;
  height: 1em;
  background: var(--ai-primary);
  margin-left: 2px;
  vertical-align: text-bottom;
  animation: blink 0.6s infinite;
}

@keyframes blink {
  0%, 100% { opacity: 1; }
  50% { opacity: 0; }
}

/* ========== 选项卡片 ========== */
.options-group {
  display: flex;
  flex-direction: column;
  gap: 8px;
  animation: fadeInUp 0.4s ease-out;
}

.options-label {
  font-size: 12px;
  color: var(--text-secondary);
  margin-bottom: 4px;
  padding-left: 42px;
}

.options-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
  padding-left: 42px;
}

.option-card {
  padding: 10px 14px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: var(--bg);
  font-size: 13px;
  color: var(--text);
  cursor: pointer;
  transition: all 0.3s;
  text-align: center;
  font-weight: 500;
}

.option-card:hover {
  border-color: var(--accent);
  background: var(--bg-tertiary);
  transform: translateY(-1px);
  box-shadow: var(--shadow-card-hover);
}

.option-card.selected {
  border-color: var(--accent);
  background: var(--accent);
  color: #fff;
}

.option-card.disabled {
  opacity: 0.4;
  pointer-events: none;
}

/* ========== 结果卡片 ========== */
.result-card {
  margin: 8px 0;
  padding: 20px;
  border-radius: 16px;
  border: 1px solid var(--border);
  background: var(--bg);
  animation: fadeInUp 0.5s ease-out;
}

.result-card-header {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 12px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--border);
}

.result-card-badge {
  font-size: 11px;
  font-weight: 600;
  padding: 3px 10px;
  border-radius: 9999px;
}

.result-card-badge.basic {
  background: var(--bg-tertiary);
  color: var(--text-secondary);
}

.result-card-badge.pro {
  background: linear-gradient(135deg, var(--ai-primary), var(--ai-secondary));
  color: #fff;
}

.result-card-title {
  font-size: 14px;
  font-weight: 600;
  color: var(--text);
}

.result-card-body {
  font-size: 13px;
  line-height: 1.8;
  color: var(--text);
}

.result-card-body .dim {
  color: var(--text-secondary);
}

.result-card-body .highlight {
  color: var(--ai-primary);
  font-weight: 600;
}

.result-section {
  margin-bottom: 12px;
}

.result-section:last-child { margin-bottom: 0; }

.result-section-title {
  font-size: 12px;
  font-weight: 600;
  color: var(--accent);
  margin-bottom: 4px;
  display: flex;
  align-items: center;
  gap: 6px;
}

.result-section-title::before {
  content: '';
  width: 3px;
  height: 12px;
  border-radius: 2px;
  background: var(--accent);
}

/* ========== 引导提示 ========== */
.guide-hint {
  text-align: center;
  padding: 16px;
  animation: fadeInUp 0.5s ease-out;
}

.guide-hint-text {
  font-size: 13px;
  color: var(--text-secondary);
  margin-bottom: 10px;
}

.guide-hint-btn {
  padding: 8px 20px;
  border-radius: 9999px;
  font-size: 13px;
  font-weight: 500;
  border: 1px solid var(--accent);
  background: transparent;
  color: var(--accent);
  cursor: pointer;
  transition: all 0.3s;
}

.guide-hint-btn:hover {
  background: var(--accent);
  color: #fff;
}

/* ========== 对比总结区 ========== */
.comparison-section {
  position: relative;
  z-index: 10;
  max-width: 960px;
  margin: 0 auto;
  padding: 0 24px 48px;
  width: 100%;
  display: none;
}

.comparison-section.visible { display: block; animation: fadeInUp 0.6s ease-out; }

.comparison-title {
  text-align: center;
  font-size: 22px;
  font-weight: 700;
  margin-bottom: 8px;
  color: var(--text);
}

.comparison-subtitle {
  text-align: center;
  font-size: 14px;
  color: var(--text-secondary);
  margin-bottom: 32px;
}

/* 数据对比表 */
.compare-table {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin-bottom: 40px;
}

.compare-col {
  border-radius: 16px;
  border: 1px solid var(--border);
  overflow: hidden;
}

.compare-col-header {
  padding: 16px 20px;
  font-size: 14px;
  font-weight: 600;
  text-align: center;
  border-bottom: 1px solid var(--border);
}

.compare-col.normal .compare-col-header {
  background: var(--bg-tertiary);
  color: var(--text-secondary);
}

.compare-col.plan .compare-col-header {
  background: linear-gradient(135deg, var(--ai-primary), var(--ai-secondary));
  color: #fff;
}

.compare-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 12px 20px;
  border-bottom: 1px solid var(--border);
  font-size: 13px;
}

.compare-row:last-child { border-bottom: none; }

.compare-label { color: var(--text-secondary); }

.compare-value {
  font-weight: 600;
  color: var(--text);
  font-variant-numeric: tabular-nums;
}

.compare-col.plan .compare-value { color: var(--ai-primary); }

/* 评分条 */
.score-bar {
  display: flex;
  align-items: center;
  gap: 8px;
}

.score-bar-track {
  width: 60px;
  height: 6px;
  border-radius: 3px;
  background: var(--bg-tertiary);
  overflow: hidden;
}

.score-bar-fill {
  height: 100%;
  border-radius: 3px;
  transition: width 1.2s cubic-bezier(0.16, 1, 0.3, 1);
  width: 0;
}

.compare-col.normal .score-bar-fill { background: var(--text-secondary); }
.compare-col.plan .score-bar-fill { background: linear-gradient(90deg, var(--ai-primary), var(--ai-secondary)); }

/* Takeaway */
.takeaway-list {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.takeaway-item {
  padding: 20px 24px;
  border-radius: 16px;
  border: 1px solid var(--border);
  background: var(--bg-secondary);
  animation: fadeInUp 0.5s ease-out backwards;
}

.takeaway-item:nth-child(1) { animation-delay: 0.1s; }
.takeaway-item:nth-child(2) { animation-delay: 0.2s; }
.takeaway-item:nth-child(3) { animation-delay: 0.3s; }

.takeaway-number {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 24px;
  height: 24px;
  border-radius: 8px;
  background: var(--accent);
  color: #fff;
  font-size: 12px;
  font-weight: 700;
  margin-right: 12px;
  flex-shrink: 0;
}

.takeaway-title {
  font-size: 15px;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 6px;
  display: flex;
  align-items: center;
}

.takeaway-desc {
  font-size: 13px;
  color: var(--text-secondary);
  line-height: 1.7;
  padding-left: 36px;
}

/* ========== Footer ========== */
.footer {
  position: relative;
  z-index: 10;
  margin-top: auto;
  padding: 32px 24px;
  text-align: center;
}

.footer p {
  font-size: 11px;
  color: var(--text-secondary);
  opacity: 0.2;
  font-weight: 300;
  letter-spacing: 0.15em;
}

/* ========== 动画 ========== */
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(12px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ========== 响应式 ========== */
@media (max-width: 640px) {
  .hero h1 { font-size: 22px; }
  .hero p { font-size: 14px; }
  .msg { max-width: 92%; }
  .options-grid {
    grid-template-columns: 1fr;
    padding-left: 0;
  }
  .options-label { padding-left: 0; }
  .compare-table {
    grid-template-columns: 1fr;
  }
  .tab-btn { padding: 8px 16px; font-size: 12px; }
  .demo-chat { padding: 14px; }
  .result-card { padding: 16px; }
}