body {
  margin: 0;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  background: var(--bg, #f7f8fa);
  color: var(--text, #222);
  transition: background 0.3s, color 0.3s;
  line-height: 1.6;
}

:root {
  --primary: #2d8cf0;
  --primary-dark: #1769aa;
  --bg: #f7f8fa;
  --text: #222;
  --panel: #fff;
  --panel-shadow: 0 2px 16px rgba(0,0,0,0.06);
  --panel-radius: 16px;
  --panel-border: none;
  --success: #27ae60;
  --warning: #f39c12;
  --error: #e74c3c;
  --info: #3498db;
}
body.dark {
  --primary: #1e90ff;
  --primary-dark: #005fa3;
  --bg: #181c20;
  --text: #eaeaea;
  --panel: #23272e;
  --panel-shadow: 0 2px 16px rgba(0,0,0,0.18);
  --panel-border: 1px solid #333;
  --success: #2ecc71;
  --warning: #f1c40f;
  --error: #e74c3c;
  --info: #3498db;
}

.container {
  max-width: 700px;
  margin: 40px auto 0 auto;
  padding: 24px;
  background: var(--panel);
  border-radius: var(--panel-radius);
  box-shadow: var(--panel-shadow);
  border: var(--panel-border);
  transition: background 0.3s, color 0.3s;
}

.navbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: var(--panel);
  padding: 0 32px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.04);
  height: 60px;
  transition: background 0.3s;
  position: sticky;
  top: 0;
  z-index: 100;
}
.nav-logo {
  font-weight: bold;
  font-size: 1.3em;
  color: var(--primary);
  cursor: pointer;
  transition: color 0.2s;
}
.nav-logo:hover {
  color: var(--primary-dark);
}
.nav-links {
  list-style: none;
  display: flex;
  gap: 24px;
  margin: 0;
  padding: 0;
  flex-wrap: wrap;
}
.nav-links a {
  text-decoration: none;
  color: var(--text);
  font-weight: 500;
  transition: color 0.2s;
  white-space: nowrap;
}
.nav-links a.active,
.nav-links a:hover {
  color: var(--primary);
}

.feature-list {
  list-style: none;
  padding: 0;
  margin: 32px 0 0 0;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 18px;
}
.feature-list li {
  background: var(--panel);
  border-radius: 12px;
  padding: 20px;
  text-align: center;
  font-size: 1.1em;
  transition: all 0.2s;
  box-shadow: 0 2px 8px rgba(0,0,0,0.04);
  border: 1px solid transparent;
}
.feature-list li:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(45,140,240,0.12);
  border-color: var(--primary);
}
.feature-list a {
  color: var(--primary);
  text-decoration: none;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
}

button, input, select, textarea, a {
  transition: background 0.2s, color 0.2s, border 0.2s, box-shadow 0.2s, transform 0.2s;
}
button:active, .calc-btn:active, .pomodoro-btn:active, .gen-btn:active, .qr-btn:active, .fc-btn:active, .game-btn:active, .txt-btn:active, .password-btn:active, .color-btn:active {
  transform: scale(0.97);
}

input, select, textarea {
  border: 1px solid #ddd;
  border-radius: 8px;
  padding: 10px 12px;
  font-size: 1em;
  margin-bottom: 10px;
  background: var(--panel);
  color: var(--text);
  transition: border-color 0.2s, box-shadow 0.2s;
}
input:focus, textarea:focus, select:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(45,140,240,0.1);
}

/* 错误提示、空态提示 */
.error-tip {
  color: var(--error);
  background: rgba(231, 76, 60, 0.1);
  border-radius: 8px;
  padding: 12px 16px;
  margin: 12px 0;
  font-size: 1em;
  border-left: 4px solid var(--error);
}
.empty-tip {
  color: #888;
  background: var(--bg);
  border-radius: 8px;
  padding: 12px 16px;
  margin: 12px 0;
  font-size: 1em;
  text-align: center;
  font-style: italic;
}

/* 成功提示 */
.success-tip {
  color: var(--success);
  background: rgba(39, 174, 96, 0.1);
  border-radius: 8px;
  padding: 12px 16px;
  margin: 12px 0;
  font-size: 1em;
  border-left: 4px solid var(--success);
}

/* 警告提示 */
.warning-tip {
  color: var(--warning);
  background: rgba(243, 156, 18, 0.1);
  border-radius: 8px;
  padding: 12px 16px;
  margin: 12px 0;
  font-size: 1em;
  border-left: 4px solid var(--warning);
}

footer {
  text-align: center;
  color: #888;
  margin: 40px 0 16px 0;
  font-size: 0.95em;
}

/* 滚动条样式 */
::-webkit-scrollbar {
  width: 8px;
}
::-webkit-scrollbar-track {
  background: var(--bg);
}
::-webkit-scrollbar-thumb {
  background: var(--primary);
  border-radius: 4px;
}
::-webkit-scrollbar-thumb:hover {
  background: var(--primary-dark);
}

/* 选择文本样式 */
::selection {
  background: var(--primary);
  color: white;
}

/* 移动端优化 */
@media (max-width: 768px) {
  .container {
    margin: 20px 10px 0 10px;
    padding: 16px;
    border-radius: 12px;
  }
  
  .navbar {
    flex-direction: column;
    height: auto;
    padding: 12px 16px;
    gap: 12px;
  }
  
  .nav-links {
    gap: 16px;
    justify-content: center;
    flex-wrap: wrap;
  }
  
  .nav-links a {
    font-size: 0.9em;
  }
  
  .feature-list {
    grid-template-columns: 1fr;
    gap: 12px;
  }
  
  .feature-list li {
    padding: 16px;
    font-size: 1em;
  }
  
  h1, h2 { 
    font-size: 1.3em; 
    margin: 16px 0 8px 0;
  }
  
  h3 { 
    font-size: 1.1em; 
    margin: 12px 0 6px 0;
  }
  
  button, input, select, textarea { 
    font-size: 16px; /* 防止iOS缩放 */
    padding: 12px 16px;
  }
  
  /* 移动端按钮优化 */
  button {
    min-height: 44px;
    min-width: 44px;
  }
  
  /* 移动端表单优化 */
  input, select, textarea {
    min-height: 44px;
  }
}

@media (max-width: 480px) {
  .container {
    margin: 10px 5px 0 5px;
    padding: 12px;
  }
  
  .navbar {
    padding: 8px 12px;
  }
  
  .nav-links {
    gap: 12px;
  }
  
  .nav-links a {
    font-size: 0.85em;
  }
  
  .feature-list li {
    padding: 12px;
  }
  
  h1 { font-size: 1.2em; }
  h2 { font-size: 1.1em; }
  h3 { font-size: 1em; }
}

/* 打印样式 */
@media print {
  .navbar {
    display: none;
  }
  
  .container {
    box-shadow: none;
    border: 1px solid #ccc;
  }
  
  button {
    display: none;
  }
}

/* 高对比度模式支持 */
@media (prefers-contrast: high) {
  :root {
    --primary: #0066cc;
    --text: #000;
    --bg: #fff;
    --panel: #fff;
  }
  
  body.dark {
    --primary: #66b3ff;
    --text: #fff;
    --bg: #000;
    --panel: #000;
  }
}

/* 减少动画模式支持 */
@media (prefers-reduced-motion: reduce) {
  * {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}