/* ===== 顶栏 ===== */
    .top-bar {
        position: fixed;
        top: 0; left: 0; right: 0;
        height: 56px;
        background: var(--card);
        border-bottom: 1px solid var(--border-light);
        z-index: 100;
        display: flex;
        align-items: center;
        justify-content: space-between;
        padding: 0 24px;
    }
    .top-bar-brand {
        display: flex;
        align-items: center;
        gap: 12px;
    }
    .top-bar-brand .logo {
        width: 32px; height: 32px;
        background: var(--brand);
        border-radius: var(--radius-sm);
        display: flex; align-items: center; justify-content: center;
        font-size: 16px; color: white; font-weight: 700;
    }
    .top-bar-brand .title {
        font-size: 16px; font-weight: 600; color: var(--text);
    }
    .top-bar-brand .slogan {
        font-size: 12px; color: var(--text-muted); margin-left: 4px;
        display: none;
    }
    @media (min-width: 900px) {
        .top-bar-brand .slogan { display: inline; }
    }
    .top-bar-user {
        display: flex;
        align-items: center;
        gap: 12px;
    }
    .balance-pill {
        background: var(--brand-light);
        color: var(--brand);
        padding: 4px 12px;
        border-radius: 20px;
        font-size: 13px;
        font-weight: 600;
    }

/* ===== 左侧导航 ===== */
    .side-nav {
        position: fixed;
        top: 56px; left: 0; bottom: 0;
        width: 220px;
        background: var(--card);
        border-right: 1px solid var(--border-light);
        overflow-y: auto;
        padding: 12px 0;
        z-index: 90;
        display: flex;
        flex-direction: column;
    }
    .nav-group {
        margin-bottom: 4px;
        padding: 0 12px;
    }
    .nav-group-title {
        font-size: 11px;
        font-weight: 600;
        color: var(--text-muted);
        text-transform: uppercase;
        letter-spacing: 0.5px;
        padding: 8px 12px 4px;
    }
    .nav-item {
        display: flex;
        align-items: center;
        gap: 10px;
        padding: 8px 12px;
        margin: 2px 0;
        border-radius: var(--radius-sm);
        font-size: 13px;
        color: var(--text-secondary);
        cursor: pointer;
        transition: all 0.15s;
        position: relative;
    }
    .nav-item:hover {
        background: var(--brand-light);
        color: var(--brand);
    }
    .nav-item.active {
        background: var(--brand-light);
        color: var(--brand);
        font-weight: 600;
    }
    .nav-item .nav-icon {
        font-size: 15px;
        width: 20px;
        text-align: center;
        flex-shrink: 0;
    }
    .nav-item .nav-badge {
        margin-left: auto;
        font-size: 10px;
        padding: 2px 6px;
        border-radius: 4px;
        font-weight: 600;
        white-space: nowrap;
    }
    .nav-item .nav-badge.free {
        background: var(--free-light);
        color: var(--free);
    }
    .nav-item .nav-badge.ad {
        background: var(--ad-light);
        color: var(--ad);
    }
    .nav-item .nav-badge.pro {
        background: var(--brand-light);
        color: var(--brand);
    }
    .nav-spacer { flex: 1; }

/* ===== 移动端菜单 ===== */
    .mobile-menu-btn {
        display: none;
        position: fixed;
        top: 60px; left: 12px;
        z-index: 95;
        width: 36px; height: 36px;
        border-radius: var(--radius-sm);
        background: var(--card);
        border: 1px solid var(--border);
        font-size: 18px;
        cursor: pointer;
        box-shadow: var(--shadow-md);
    }
    .nav-overlay {
        display: none;
        position: fixed;
        top: 56px; left: 0; right: 0; bottom: 0;
        background: rgba(0,0,0,0.3);
        z-index: 85;
    }
    .nav-overlay.show { display: block; }

/* ===== 主内容区 ===== */
    .main-content {
        margin-left: 220px;
        margin-top: 56px;
        padding: 24px;
        min-height: calc(100vh - 56px);
    }

/* ===== 响应式 ===== */
    @media (max-width: 768px) {
        .side-nav {
            transform: translateX(-100%);
            transition: transform 0.3s;
            box-shadow: 2px 0 12px rgba(0,0,0,0.1);
        }
        .side-nav.show-mobile {
            transform: translateX(0);
        }
        .main-content {
            margin-left: 0;
            padding: 16px;
        }
        .mobile-menu-btn { display: block; }
        .main-card { padding: 20px; }
        .tier-cards { grid-template-columns: 1fr; }
    }
    @media (max-width: 480px) {
        .top-bar { padding: 0 16px; }
        .main-card { padding: 16px; border-radius: var(--radius-md); }
        .upload-area { padding: 40px 16px; }
        .recharge-options { grid-template-columns: repeat(2, 1fr); }
    }