/* =============================================
 * 暗色模式系统
 * CSS 变量驱动的双主题，仅用 JavaScript 做切换和持久化
 * ============================================= */

:root {
  /* 亮色主题（默认） */
  --bg-primary: #f8f9fa;
  --bg-secondary: #ffffff;
  --bg-tertiary: #f0f2f5;
  --bg-overlay: rgba(0,0,0,0.5);
  --bg-card: #ffffff;
  --bg-input: #ffffff;
  --bg-table-header: #667eea;
  --bg-table-row-even: #f8f9ff;
  --bg-table-row-hover: #eef0ff;

  --text-primary: #2c3e50;
  --text-secondary: #495057;
  --text-muted: #868e96;
  --text-inverse: #ffffff;
  --text-link: #4dabf7;

  --border-color: #e9ecef;
  --border-light: #f1f3f5;

  --accent-primary: #667eea;
  --accent-secondary: #764ba2;
  --accent-success: #51cf66;
  --accent-warning: #ffd43b;
  --accent-danger: #ff6b6b;

  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
  --shadow-lg: 0 8px 30px rgba(0,0,0,0.12);

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
}

[data-theme="dark"] {
  --bg-primary: #1a1a2e;
  --bg-secondary: #16213e;
  --bg-tertiary: #0f3460;
  --bg-overlay: rgba(0,0,0,0.7);
  --bg-card: #1e2746;
  --bg-input: #2a2a4a;
  --bg-table-header: #4a4a8a;
  --bg-table-row-even: #1e2240;
  --bg-table-row-hover: #252d55;

  --text-primary: #e4e6f0;
  --text-secondary: #c0c4d8;
  --text-muted: #7a7fa0;
  --text-inverse: #ffffff;
  --text-link: #74c0fc;

  --border-color: #2a3555;
  --border-light: #1f2844;

  --accent-primary: #748ffc;
  --accent-secondary: #b197fc;
  --accent-success: #69db7c;
  --accent-warning: #ffd43b;
  --accent-danger: #ff8787;

  --shadow-sm: 0 1px 3px rgba(0,0,0,0.3);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.4);
  --shadow-lg: 0 8px 30px rgba(0,0,0,0.5);
}

/* 主题切换按钮 */
.theme-toggle {
  position: fixed;
  top: 16px;
  right: 80px;
  z-index: 1000;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: var(--bg-secondary);
  border: 2px solid var(--border-color);
  color: var(--text-primary);
  cursor: pointer;
  font-size: 18px;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-sm);
  transition: transform 0.2s, box-shadow 0.2s;
}
.theme-toggle:hover {
  transform: scale(1.1);
  box-shadow: var(--shadow-md);
}

/* 全局过渡 */
body, .panel, .modal, .modal-overlay, button, input, select, textarea,
.card, .table, .group-card, .student-row, [class*="bg-"], [class*="color-"] {
  transition: background-color 0.3s ease, color 0.3s ease, border-color 0.3s ease, box-shadow 0.3s ease;
}