:root {
    --bg-primary: #000000;
    --text-primary: #ffffff;
    --text-secondary: #888888;
    --accent-cyan: #4ecdc4;
    --accent-orange: #ff8c42;
    --nav-height: 50px;
}
* { margin: 0; padding: 0; box-sizing: border-box; }
html, body {
    width: 100%; height: 100%;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "PingFang SC", "Microsoft YaHei", sans-serif;
    overflow: hidden;
}
.top-nav {
    position: fixed;
    top: 0; right: 0;
    height: var(--nav-height);
    display: flex;
    align-items: center;
    gap: 24px;
    padding: 0 30px;
    z-index: 1000;
    background: linear-gradient(to bottom, rgba(0,0,0,0.9) 0%, transparent 100%);
}
.nav-item {
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 14px;
    letter-spacing: 2px;
    padding-bottom: 4px;
    border-bottom: 1px solid transparent;
    transition: all 0.3s ease;
    background: none;
    border: none;
    cursor: pointer;
    font-family: inherit;
}
.nav-item:hover { color: var(--text-primary); }
.nav-item.active {
    color: var(--text-primary);
    border-bottom-color: var(--text-primary);
}
.fullscreen-btn { margin-left: 10px; }
.ai-tools {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: #fff;
    padding: 6px 16px;
    border-radius: 20px;
    font-weight: 600;
    letter-spacing: 1px;
    text-shadow: 0 1px 2px rgba(0,0,0,0.3);
    box-shadow: 0 2px 10px rgba(102, 126, 234, 0.4);
    animation: aiPulse 2s ease-in-out infinite;
}
.ai-tools:hover {
    background: linear-gradient(135deg, #7b8ff0 0%, #8a5cb3 100%);
    box-shadow: 0 4px 20px rgba(102, 126, 234, 0.6);
    transform: translateY(-1px);
}
@keyframes aiPulse {
    0%, 100% { box-shadow: 0 2px 10px rgba(102, 126, 234, 0.4); }
    50% { box-shadow: 0 2px 20px rgba(102, 126, 234, 0.7); }
}
.fav-btn {
    /* 和其他导航项一致 */
}

/* 字体优化 */
body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'Helvetica Neue', Helvetica, Arial, sans-serif;
}

/* 时钟等宽字体 */
.clock-font, .time, .current-time, .center-display .time {
    font-family: 'Courier New', 'SF Mono', 'Monaco', 'Inconsolata', 'Fira Code', monospace;
    font-variant-numeric: tabular-nums;
}