/* ====================================
   简约自适应样式 - 补课视频管理系统
   ==================================== */

:root {
    --primary: #4f46e5;
    --primary-hover: #4338ca;
    --primary-light: #eef2ff;
    --success: #10b981;
    --warning: #f59e0b;
    --danger: #ef4444;
    --gray-50: #f9fafb;
    --gray-100: #f3f4f6;
    --gray-200: #e5e7eb;
    --gray-300: #d1d5db;
    --gray-400: #9ca3af;
    --gray-500: #6b7280;
    --gray-600: #4b5563;
    --gray-700: #374151;
    --gray-800: #1f2937;
    --gray-900: #111827;
    --radius: 12px;
    --radius-sm: 8px;
    --shadow: 0 1px 3px rgba(0,0,0,.06), 0 1px 2px rgba(0,0,0,.04);
    --shadow-lg: 0 10px 15px -3px rgba(0,0,0,.08), 0 4px 6px -2px rgba(0,0,0,.04);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Noto Sans SC', sans-serif;
    background: var(--gray-50);
    color: var(--gray-800);
    line-height: 1.6;
    min-height: 100vh;
}

a {
    color: var(--primary);
    text-decoration: none;
}

a:hover {
    color: var(--primary-hover);
}

/* ---- Login Pages ---- */
.login-page {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    padding: 20px;
}

.login-card {
    background: #fff;
    border-radius: var(--radius);
    box-shadow: var(--shadow-lg);
    padding: 40px;
    width: 100%;
    max-width: 400px;
}

.login-card .logo {
    text-align: center;
    margin-bottom: 32px;
}

.login-card .logo h1 {
    font-size: 24px;
    color: var(--gray-800);
    font-weight: 700;
}

.login-card .logo p {
    color: var(--gray-400);
    font-size: 14px;
    margin-top: 4px;
}

.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 6px;
    font-size: 14px;
    font-weight: 500;
    color: var(--gray-700);
}

.form-input {
    width: 100%;
    padding: 10px 14px;
    border: 1.5px solid var(--gray-200);
    border-radius: var(--radius-sm);
    font-size: 15px;
    transition: border-color .2s, box-shadow .2s;
    background: #fff;
    outline: none;
}

.form-input:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(79,70,229,.12);
}

.form-input.error {
    border-color: var(--danger);
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 10px 20px;
    border-radius: var(--radius-sm);
    font-size: 14px;
    font-weight: 500;
    border: none;
    cursor: pointer;
    transition: all .2s;
    text-decoration: none;
    line-height: 1.4;
}

.btn-primary {
    background: var(--primary);
    color: #fff;
}

.btn-primary:hover {
    background: var(--primary-hover);
    color: #fff;
}

.btn-success {
    background: var(--success);
    color: #fff;
}

.btn-success:hover {
    background: #059669;
    color: #fff;
}

.btn-warning {
    background: var(--warning);
    color: #fff;
}

.btn-warning:hover {
    background: #d97706;
    color: #fff;
}

.btn-danger {
    background: var(--danger);
    color: #fff;
}

.btn-danger:hover {
    background: #dc2626;
    color: #fff;
}

.btn-sm {
    padding: 6px 12px;
    font-size: 13px;
}

.btn-block {
    width: 100%;
}

.btn-outline {
    background: transparent;
    border: 1.5px solid var(--gray-200);
    color: var(--gray-700);
}

.btn-outline:hover {
    border-color: var(--primary);
    color: var(--primary);
    background: var(--primary-light);
}

/* ---- Admin Layout ---- */
.admin-layout {
    display: flex;
    min-height: 100vh;
}

.sidebar {
    width: 240px;
    background: #fff;
    border-right: 1px solid var(--gray-200);
    display: flex;
    flex-direction: column;
    position: fixed;
    top: 0;
    left: 0;
    bottom: 0;
    z-index: 100;
    transition: transform .3s;
}

.sidebar-header {
    padding: 20px 24px;
    border-bottom: 1px solid var(--gray-200);
}

.sidebar-header h2 {
    font-size: 18px;
    font-weight: 700;
    color: var(--primary);
}

.sidebar-header small {
    color: var(--gray-400);
    font-size: 12px;
}

.sidebar-nav {
    flex: 1;
    padding: 12px 12px;
    overflow-y: auto;
}

.nav-item {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 10px 14px;
    border-radius: var(--radius-sm);
    color: var(--gray-600);
    font-size: 14px;
    font-weight: 500;
    margin-bottom: 2px;
    transition: all .15s;
}

.nav-item:hover {
    background: var(--gray-100);
    color: var(--gray-800);
}

.nav-item.active {
    background: var(--primary-light);
    color: var(--primary);
    font-weight: 600;
}

.nav-item .icon {
    width: 20px;
    text-align: center;
    font-size: 16px;
}

.sidebar-footer {
    padding: 16px 12px;
    border-top: 1px solid var(--gray-200);
}

.main-content {
    flex: 1;
    margin-left: 240px;
    min-height: 100vh;
}

.topbar {
    background: #fff;
    border-bottom: 1px solid var(--gray-200);
    padding: 12px 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    position: sticky;
    top: 0;
    z-index: 50;
}

.topbar h3 {
    font-size: 16px;
    font-weight: 600;
}

.topbar .admin-info {
    display: flex;
    align-items: center;
    gap: 12px;
    font-size: 14px;
    color: var(--gray-500);
}

.page-content {
    padding: 24px;
}

/* ---- Cards ---- */
.card {
    background: #fff;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    overflow: hidden;
}

.card-header {
    padding: 16px 20px;
    border-bottom: 1px solid var(--gray-100);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.card-header h4 {
    font-size: 15px;
    font-weight: 600;
}

.card-body {
    padding: 20px;
}

/* ---- Table ---- */
.table-wrap {
    overflow-x: auto;
}

table {
    width: 100%;
    border-collapse: collapse;
    font-size: 14px;
}

table th {
    background: var(--gray-50);
    padding: 10px 14px;
    text-align: left;
    font-weight: 600;
    color: var(--gray-600);
    border-bottom: 2px solid var(--gray-200);
    white-space: nowrap;
}

table td {
    padding: 10px 14px;
    border-bottom: 1px solid var(--gray-100);
    vertical-align: middle;
}

table tr:hover td {
    background: var(--gray-50);
}

.table-actions {
    display: flex;
    gap: 6px;
    flex-wrap: wrap;
}

/* ---- Badge ---- */
.badge {
    display: inline-flex;
    align-items: center;
    padding: 2px 8px;
    border-radius: 20px;
    font-size: 12px;
    font-weight: 500;
}

.badge-success {
    background: #d1fae5;
    color: #065f46;
}

.badge-warning {
    background: #fef3c7;
    color: #92400e;
}

.badge-danger {
    background: #fee2e2;
    color: #991b1b;
}

.badge-info {
    background: #dbeafe;
    color: #1e40af;
}

/* ---- Pagination ---- */
.pagination {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 4px;
    margin-top: 20px;
    padding: 10px 0;
}

.pagination a, .pagination span {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-width: 36px;
    height: 36px;
    padding: 0 8px;
    border: 1px solid var(--gray-200);
    border-radius: var(--radius-sm);
    font-size: 14px;
    color: var(--gray-600);
    transition: all .15s;
}

.pagination a:hover {
    border-color: var(--primary);
    color: var(--primary);
    background: var(--primary-light);
}

.pagination .current {
    background: var(--primary);
    color: #fff;
    border-color: var(--primary);
}

/* ---- Toast / Flash ---- */
.toast {
    position: fixed;
    top: 20px;
    right: 20px;
    z-index: 9999;
    padding: 12px 20px;
    border-radius: var(--radius-sm);
    color: #fff;
    font-size: 14px;
    font-weight: 500;
    box-shadow: var(--shadow-lg);
    animation: slideIn .3s ease;
    max-width: 360px;
}

.toast-success {
    background: var(--success);
}

.toast-error {
    background: var(--danger);
}

@keyframes slideIn {
    from { transform: translateX(100%); opacity: 0; }
    to { transform: translateX(0); opacity: 1; }
}

/* ---- Alert ---- */
.alert {
    padding: 12px 16px;
    border-radius: var(--radius-sm);
    font-size: 14px;
    margin-bottom: 16px;
}

.alert-success {
    background: #d1fae5;
    color: #065f46;
    border: 1px solid #a7f3d0;
}

.alert-error {
    background: #fee2e2;
    color: #991b1b;
    border: 1px solid #fecaca;
}

/* ---- Student Video Cards ---- */
.video-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 20px;
}

.video-card {
    background: #fff;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    overflow: hidden;
    transition: box-shadow .2s;
}

.video-card:hover {
    box-shadow: var(--shadow-lg);
}

.video-card .video-wrapper {
    position: relative;
    padding-top: 56.25%;
    background: #000;
}

.video-card .video-wrapper video,
.video-card .video-wrapper iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: none;
}

.video-card .video-info {
    padding: 16px;
}

.video-card .video-info h3 {
    font-size: 16px;
    font-weight: 600;
    margin-bottom: 4px;
}

.video-card .video-info .lesson-tag {
    display: inline-block;
    background: var(--primary-light);
    color: var(--primary);
    padding: 2px 8px;
    border-radius: 4px;
    font-size: 12px;
    font-weight: 500;
    margin-bottom: 8px;
}

.video-card .video-info .desc {
    color: var(--gray-500);
    font-size: 13px;
    margin-bottom: 12px;
}

.video-card .video-info .meta {
    display: flex;
    align-items: center;
    justify-content: space-between;
    font-size: 13px;
    color: var(--gray-500);
}

.video-card .video-info .status-bar {
    margin-top: 12px;
    padding-top: 12px;
    border-top: 1px solid var(--gray-100);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

/* ---- Student Top Bar ---- */
.student-topbar {
    background: #fff;
    border-bottom: 1px solid var(--gray-200);
    padding: 12px 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    position: sticky;
    top: 0;
    z-index: 50;
}

.student-topbar .logo {
    font-size: 18px;
    font-weight: 700;
    color: var(--primary);
}

.student-topbar .user-menu {
    display: flex;
    align-items: center;
    gap: 16px;
}

.student-topbar .user-menu .username {
    font-size: 14px;
    color: var(--gray-600);
}

/* ---- Form Inline ---- */
.form-row {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 16px;
}

.form-actions {
    display: flex;
    gap: 8px;
    margin-top: 24px;
    padding-top: 16px;
    border-top: 1px solid var(--gray-100);
}

/* ---- Checkbox / Select ---- */
.form-select {
    width: 100%;
    padding: 10px 14px;
    border: 1.5px solid var(--gray-200);
    border-radius: var(--radius-sm);
    font-size: 15px;
    background: #fff;
    outline: none;
    transition: border-color .2s;
    min-height: 42px;
}

.form-select:focus {
    border-color: var(--primary);
}

.checkbox-group {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    padding: 8px 0;
}

.checkbox-item {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 6px 12px;
    border: 1.5px solid var(--gray-200);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all .15s;
    font-size: 14px;
    user-select: none;
}

.checkbox-item:hover {
    border-color: var(--primary);
    background: var(--primary-light);
}

.checkbox-item.selected {
    border-color: var(--primary);
    background: var(--primary-light);
    color: var(--primary);
}

.checkbox-item input[type="checkbox"] {
    position: absolute;
    opacity: 0;
    pointer-events: none;
}

.check-icon {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 18px;
    height: 18px;
    border: 1.5px solid var(--gray-300);
    border-radius: 4px;
    font-size: 12px;
    color: #fff;
    background: #fff;
    transition: all .15s;
    flex-shrink: 0;
}

.checkbox-item.selected .check-icon {
    background: var(--primary);
    border-color: var(--primary);
    color: #fff;
}

/* ---- Empty State ---- */
.empty-state {
    text-align: center;
    padding: 60px 20px;
    color: var(--gray-400);
}

.empty-state .icon {
    font-size: 48px;
    margin-bottom: 12px;
}

.empty-state p {
    font-size: 15px;
}

/* ---- Hamburger (mobile) ---- */
.hamburger {
    display: none;
    background: none;
    border: none;
    font-size: 24px;
    cursor: pointer;
    padding: 4px;
    color: var(--gray-600);
}

.sidebar-overlay {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0,0,0,.3);
    z-index: 99;
}

/* ---- Responsive ---- */
@media (max-width: 768px) {
    .sidebar {
        transform: translateX(-100%);
    }

    .sidebar.open {
        transform: translateX(0);
    }

    .sidebar-overlay.open {
        display: block;
    }

    .main-content {
        margin-left: 0;
    }

    .hamburger {
        display: inline-block;
    }

    .page-content {
        padding: 16px;
    }

    .video-grid {
        grid-template-columns: 1fr;
    }

    .login-card {
        padding: 24px;
    }

    .form-row {
        grid-template-columns: 1fr;
    }

    .table-actions {
        flex-direction: column;
    }

    .table-actions .btn {
        width: 100%;
    }

    .student-topbar {
        padding: 10px 16px;
    }

    .topbar {
        padding: 10px 16px;
    }
}

@media (max-width: 480px) {
    .login-card {
        padding: 20px;
    }

    .card-header {
        flex-direction: column;
        gap: 8px;
    }

    .checkbox-group {
        flex-direction: column;
    }
}