/* 侧边栏 */
.sidebar {
    width: var(--sidebar-width);
    background-color: var(--bg-white);
    box-shadow: var(--shadow-sm);
    height: 100vh;
    position: fixed;
    left: 0;
    top: 0;
    z-index: 1000;
    transition: transform var(--transition-normal);
    overflow-y: auto;
    padding-top: var(--spacing-lg);
    will-change: transform;
}

.sidebar::-webkit-scrollbar { width: 6px; }
.sidebar::-webkit-scrollbar-track { background: var(--bg-light); border-radius: var(--border-radius-sm); }
.sidebar::-webkit-scrollbar-thumb { background: #ddd; border-radius: var(--border-radius-sm); }
.sidebar { scrollbar-width: thin; scrollbar-color: #ddd var(--bg-light); }

.sidebar-title {
    font-size: 18px;
    font-weight: 600;
    color: var(--text-primary);
    padding: 0 var(--spacing-lg) var(--spacing-sm);
    border-bottom: 1px solid var(--border-light);
    margin-bottom: var(--spacing-sm);
}

.sidebar-menu { list-style: none; }
.sidebar-menu-item { margin-bottom: var(--spacing-xxs); }
.sidebar-menu-link {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px var(--spacing-lg);
    color: var(--text-secondary);
    text-decoration: none;
    cursor: pointer;
    border-left: 3px solid transparent;
    position: relative;
    z-index: 1;
    tabindex: 0;
    aria-label: "切换到{sidebar-menu-text}";
}

.sidebar-menu-link:hover, .sidebar-menu-link.active {
    background-color: #f5fafe;
    color: var(--color-primary);
    border-left-color: var(--color-primary);
}

.sidebar-menu-icon { font-size: 20px; }

/* 主内容区 */
.main-content {
    flex: 1;
    margin-left: var(--sidebar-width);
    width: calc(100% - var(--sidebar-width));
    transition: margin-left var(--transition-normal), width var(--transition-normal);
}

/* 头部 */
.header {
    display: flex;
    align-items: center;
    padding: var(--spacing-md) var(--spacing-lg);
    background-color: var(--bg-white);
    box-shadow: var(--shadow-xs);
    position: sticky;
    top: 0;
    z-index: 100;
    will-change: box-shadow;
    gap: var(--spacing-md);
}

body.scrolled .header { box-shadow: var(--shadow-sm); }
.header-title-wrapper {
    flex: 1;
    text-align: center;
    min-width: 0;
}

.title { font-size: 22px; font-weight: 600; color: var(--text-primary); }

/* 菜单按钮 */
.menu-btn {
    background-color: var(--color-primary);
    color: var(--bg-white);
    border: none;
    width: 40px;
    height: 40px;
    border-radius: var(--border-radius-circle);
    font-size: 20px;
    cursor: pointer;
    display: none;
    align-items: center;
    justify-content: center;
    position: static;
    transform: none;
    z-index: 1;
    box-shadow: 0 2px 8px rgba(64, 158, 255, 0.3);
    outline: none;
    flex-shrink: 0;
    aria-label: "切换侧边栏";
}

.menu-btn:hover {
    background-color: #66b1ff;
    box-shadow: 0 2px 12px rgba(64, 158, 255, 0.5);
    transform: scale(1.05);
}

.menu-btn:active { transform: scale(0.95); }