/* ============================================
   在线考试系统 - 全局样式
   ============================================ */

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

:root {
    --primary: #4f46e5;
    --primary-hover: #4338ca;
    --primary-light: #e0e7ff;
    --success: #10b981;
    --success-light: #d1fae5;
    --danger: #ef4444;
    --danger-light: #fee2e2;
    --warning: #f59e0b;
    --warning-light: #fef3c7;
    --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: 8px;
    --shadow: 0 1px 3px rgba(0,0,0,0.1), 0 1px 2px rgba(0,0,0,0.06);
    --shadow-md: 0 4px 6px rgba(0,0,0,0.07), 0 2px 4px rgba(0,0,0,0.06);
    --shadow-lg: 0 10px 15px rgba(0,0,0,0.1), 0 4px 6px rgba(0,0,0,0.05);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "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 {
    text-decoration: underline;
}

/* Cards and buttons should not show underline on hover */
a.card:hover,
a.btn:hover,
a[class*="feature-card"]:hover,
a[class*="exam-card"]:hover,
a[class*="btn-"]:hover {
    text-decoration: none;
}

/* Navigation */
.navbar {
    background: white;
    border-bottom: 1px solid var(--gray-200);
    padding: 0 1.5rem;
    height: 60px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: var(--shadow);
}

.nav-left {
    display: flex;
    align-items: center;
    gap: 2rem;
    height: 100%;
}

.site-logo {
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--primary);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    letter-spacing: -0.3px;
    padding: 0.5rem 0;
    text-decoration: none !important;
    white-space: nowrap;
}

.site-logo:hover {
    color: var(--primary-hover);
}

.nav-links {
    display: flex;
    gap: 0.25rem;
    align-items: center;
    height: 100%;
}

.nav-links a {
    color: var(--gray-500);
    font-weight: 500;
    font-size: 0.9rem;
    padding: 0 1rem;
    line-height: 60px;
    border-bottom: 2px solid transparent;
    transition: all 0.2s;
    white-space: nowrap;
}

.nav-links a:hover,
.nav-links a.active {
    color: var(--primary);
    border-bottom-color: var(--primary);
    text-decoration: none;
    background: var(--primary-light);
}

/* Right side of navbar */
.nav-right {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.user-display-name {
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--gray-700);
    padding: 0.25rem 0.75rem;
    background: var(--gray-100);
    border-radius: 20px;
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
}

.user-display-name::before {
    content: '';
    display: inline-block;
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: #22c55e;
    flex-shrink: 0;
}

/* User dropdown menu */
.user-menu {
    position: relative;
    display: inline-block;
}
.user-dropdown {
    display: none;
    position: absolute;
    top: 100%;
    right: 0;
    min-width: 140px;
    background: #fff;
    border: 1px solid #e4e7f0;
    border-radius: 8px;
    box-shadow: 0 4px 16px rgba(0,0,0,0.1);
    z-index: 1000;
    overflow: hidden;
    margin-top: 6px;
}
.user-dropdown a {
    display: block;
    padding: 10px 16px;
    font-size: 0.85em;
    color: #333;
    text-decoration: none;
    transition: background 0.15s;
}
.user-dropdown a:hover {
    background: #f5f6fa;
    color: #667eea;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.5rem 1rem;
    border-radius: var(--radius);
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    text-decoration: none;
    border: 1px solid transparent;
    transition: all 0.2s;
    gap: 0.5rem;
}

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

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

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

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

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

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

.btn-outline {
    background: white;
    color: var(--gray-700);
    border-color: var(--gray-300);
}

.btn-outline:hover {
    background: var(--gray-50);
    border-color: var(--gray-400);
}

.btn-sm {
    padding: 0.25rem 0.75rem;
    font-size: 0.8rem;
}

.btn-lg {
    padding: 0.75rem 1.5rem;
    font-size: 1rem;
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

/* Cards */
.card {
    background: white;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 1.5rem;
    transition: box-shadow 0.2s;
}

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

.card-title {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--gray-900);
    margin-bottom: 0.5rem;
}

/* Forms */
.form-group {
    margin-bottom: 1rem;
}

.form-label {
    display: block;
    font-weight: 500;
    margin-bottom: 0.375rem;
    color: var(--gray-700);
    font-size: 0.875rem;
}

.form-input,
.form-select,
.form-textarea {
    width: 100%;
    padding: 0.5rem 0.75rem;
    border: 1px solid var(--gray-300);
    border-radius: var(--radius);
    font-size: 0.875rem;
    transition: border-color 0.2s, box-shadow 0.2s;
    background: white;
}

.form-input:focus,
.form-select:focus,
.form-textarea:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px var(--primary-light);
}

.form-textarea {
    min-height: 80px;
    resize: vertical;
}

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

table {
    width: 100%;
    border-collapse: collapse;
}

th, td {
    padding: 0.75rem 1rem;
    text-align: left;
    border-bottom: 1px solid var(--gray-200);
    font-size: 0.875rem;
}

th {
    background: var(--gray-50);
    font-weight: 600;
    color: var(--gray-600);
}

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

/* Badges */
.badge {
    display: inline-block;
    padding: 0.125rem 0.5rem;
    border-radius: 9999px;
    font-size: 0.75rem;
    font-weight: 500;
}

.badge-primary { background: var(--primary-light); color: var(--primary); }
.badge-success { background: var(--success-light); color: #065f46; }
.badge-danger { background: var(--danger-light); color: #991b1b; }
.badge-warning { background: var(--warning-light); color: #92400e; }
.badge-gray { background: var(--gray-100); color: var(--gray-600); }

/* Layout */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.5rem;
}

.page-header {
    padding: 1.5rem 0;
    margin-bottom: 1.5rem;
    border-bottom: 1px solid var(--gray-200);
}

.page-header h1 {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--gray-900);
}

.page-header p {
    color: var(--gray-500);
    margin-top: 0.25rem;
}

.grid {
    display: grid;
    gap: 1rem;
}

.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-4 { grid-template-columns: repeat(4, 1fr); }

@media (max-width: 768px) {
    .grid-2, .grid-3, .grid-4 {
        grid-template-columns: 1fr;
    }
    .navbar-links {
        display: none;
    }
    /* Hide site title text on mobile */
    .site-title {
        display: none;
    }
    /* Hide register button on mobile */
    #registerBtn {
        display: none !important;
    }
    .nav-left {
        gap: 0.5rem;
    }
    .nav-links {
        gap: 0;
    }
    .nav-links a {
        padding: 0 0.5rem;
        font-size: 0.85rem;
    }
}

/* Modal */
.modal-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 99999;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.2s;
}

.modal-overlay.active {
    opacity: 1;
    pointer-events: auto;
}

.modal {
    background: white;
    border-radius: var(--radius);
    padding: 1.5rem;
    max-width: 500px;
    width: 90%;
    max-height: 80vh;
    overflow-y: auto;
    box-shadow: var(--shadow-lg);
}

.modal-title {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 1rem;
}

/* Tabs */
.tabs {
    display: flex;
    border-bottom: 2px solid var(--gray-200);
    margin-bottom: 1.5rem;
    gap: 0;
}

.tab-btn {
    padding: 0.75rem 1.25rem;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--gray-500);
    border: none;
    background: none;
    cursor: pointer;
    border-bottom: 2px solid transparent;
    margin-bottom: -2px;
    transition: all 0.2s;
}

.tab-btn:hover {
    color: var(--gray-700);
}

.tab-btn.active {
    color: var(--primary);
    border-bottom-color: var(--primary);
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
}

/* Progress bar */
.progress-bar {
    width: 100%;
    height: 8px;
    background: var(--gray-200);
    border-radius: 9999px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--primary);
    border-radius: 9999px;
    transition: width 0.3s;
}

/* Alert */
.alert {
    padding: 0.75rem 1rem;
    border-radius: var(--radius);
    margin-bottom: 1rem;
    font-size: 0.875rem;
}

.alert-success { background: var(--success-light); color: #065f46; }
.alert-danger { background: var(--danger-light); color: #991b1b; }
.alert-warning { background: var(--warning-light); color: #92400e; }
.alert-info { background: var(--primary-light); color: var(--primary); }

/* Utility */
.text-center { text-align: center; }
.text-right { text-align: right; }
.text-sm { font-size: 0.875rem; }
.text-xs { font-size: 0.75rem; }
.text-gray { color: var(--gray-500); }
.text-danger { color: var(--danger); }
.text-success { color: var(--success); }
.font-bold { font-weight: 700; }
.mt-1 { margin-top: 0.5rem; }
.mt-2 { margin-top: 1rem; }
.mt-3 { margin-top: 1.5rem; }
.mb-1 { margin-bottom: 0.5rem; }
.mb-2 { margin-bottom: 1rem; }
.mb-3 { margin-bottom: 1.5rem; }
.gap-1 { gap: 0.5rem; }
.gap-2 { gap: 1rem; }
.flex { display: flex; }
.flex-wrap { flex-wrap: wrap; }
.items-center { align-items: center; }
.justify-between { justify-content: space-between; }
.hidden { display: none !important; }

/* Footer */
footer {
    text-align: center;
    padding: 2rem 0;
    color: var(--gray-400);
    font-size: 0.8rem;
    border-top: 1px solid var(--gray-200);
    margin-top: 3rem;
}

/* Loading spinner */
.spinner {
    display: inline-block;
    width: 1.5rem;
    height: 1.5rem;
    border: 2px solid var(--gray-200);
    border-top-color: var(--primary);
    border-radius: 50%;
    animation: spin 0.6s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* Question option styles */
.option-btn {
    display: block;
    width: 100%;
    text-align: left;
    padding: 0.75rem 1rem;
    margin-bottom: 0.5rem;
    border: 2px solid var(--gray-200);
    border-radius: var(--radius);
    background: white;
    cursor: pointer;
    transition: all 0.2s;
    font-size: 0.9rem;
}

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

.option-btn.selected {
    border-color: var(--primary);
    background: var(--primary-light);
}

.option-btn.correct {
    border-color: var(--success);
    background: var(--success-light);
}

.option-btn.wrong {
    border-color: var(--danger);
    background: var(--danger-light);
}

/* Responsive */
@media (max-width: 640px) {
    .container {
        padding: 0 1rem;
    }
    .card {
        padding: 1rem;
    }
    .btn {
        padding: 0.5rem 0.75rem;
        font-size: 0.8rem;
    }
}