/* 
 * BER Learn LMS - 2026 Design System
 * Modern CSS with design tokens, dark mode, and glassmorphism
 */

/* ==========================================
   DESIGN TOKENS (CSS Custom Properties)
   ========================================== */
:root {
    /* Colors - Light Mode */
    --color-primary: #0066cc;
    --color-primary-dark: #004c99;
    --color-primary-light: #3399ff;
    --color-secondary: #00a3a3;
    --color-accent: #ff6b35;
    
    /* Neutrals */
    --color-bg-primary: #f8fafc;
    --color-bg-secondary: #ffffff;
    --color-bg-tertiary: #e2e8f0;
    --color-text-primary: #0f172a;
    --color-text-secondary: #475569;
    --color-text-muted: #94a3b8;
    --color-border: #e2e8f0;
    
    /* Status Colors */
    --color-success: #10b981;
    --color-warning: #f59e0b;
    --color-error: #ef4444;
    --color-info: #3b82f6;
    
    /* Glassmorphism */
    --glass-bg: rgba(255, 255, 255, 0.7);
    --glass-border: rgba(255, 255, 255, 0.3);
    --glass-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
    
    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 2rem;
    --font-size-4xl: 2.5rem;
    
    /* Spacing */
    --space-1: 0.25rem;
    --space-2: 0.5rem;
    --space-3: 0.75rem;
    --space-4: 1rem;
    --space-5: 1.25rem;
    --space-6: 1.5rem;
    --space-8: 2rem;
    --space-10: 2.5rem;
    --space-12: 3rem;
    --space-16: 4rem;
    
    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-2xl: 1.5rem;
    --radius-full: 9999px;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
    --transition-slow: 350ms ease;
}

/* Dark Mode */
[data-theme="dark"] {
    --color-bg-primary: #0f172a;
    --color-bg-secondary: #1e293b;
    --color-bg-tertiary: #334155;
    --color-text-primary: #f1f5f9;
    --color-text-secondary: #cbd5e1;
    --color-text-muted: #64748b;
    --color-border: #334155;
    
    --glass-bg: rgba(30, 41, 59, 0.8);
    --glass-border: rgba(255, 255, 255, 0.1);
    --glass-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
}

/* ==========================================
   BASE STYLES
   ========================================== */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--color-text-primary);
    background-color: var(--color-bg-primary);
    min-height: 100vh;
}

/* ==========================================
   TYPOGRAPHY
   ========================================== */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
    line-height: 1.3;
    color: var(--color-text-primary);
}

h1 { font-size: var(--font-size-4xl); }
h2 { font-size: var(--font-size-3xl); }
h3 { font-size: var(--font-size-2xl); }
h4 { font-size: var(--font-size-xl); }
h5 { font-size: var(--font-size-lg); }
h6 { font-size: var(--font-size-base); }

p {
    color: var(--color-text-secondary);
    margin-bottom: var(--space-4);
}

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

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

/* ==========================================
   LAYOUT COMPONENTS
   ========================================== */
.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 var(--space-6);
}

.admin-layout {
    display: grid;
    grid-template-columns: 280px 1fr;
    min-height: 100vh;
}

.admin-sidebar {
    background: var(--color-bg-secondary);
    border-right: 1px solid var(--color-border);
    padding: var(--space-6);
    position: sticky;
    top: 0;
    height: 100vh;
    overflow-y: auto;
}

.admin-main {
    padding: var(--space-8);
    background: var(--color-bg-primary);
}

/* ==========================================
   CARDS
   ========================================== */
.card {
    background: var(--color-bg-secondary);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-xl);
    padding: var(--space-6);
    box-shadow: var(--shadow-sm);
    transition: all var(--transition-base);
}

.card:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-2px);
}

.card-glass {
    background: var(--glass-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1px solid var(--glass-border);
    box-shadow: var(--glass-shadow);
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--space-4);
    padding-bottom: var(--space-4);
    border-bottom: 1px solid var(--color-border);
}

.card-title {
    font-size: var(--font-size-xl);
    font-weight: 600;
}

/* ==========================================
   BUTTONS
   ========================================== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-2);
    padding: var(--space-3) var(--space-5);
    font-size: var(--font-size-sm);
    font-weight: 500;
    border-radius: var(--radius-lg);
    border: none;
    cursor: pointer;
    transition: all var(--transition-fast);
    text-decoration: none;
}

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

.btn-primary {
    background: linear-gradient(135deg, var(--color-primary), var(--color-primary-dark));
    color: white;
}

.btn-primary:hover:not(:disabled) {
    background: linear-gradient(135deg, var(--color-primary-dark), var(--color-primary));
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.btn-secondary {
    background: var(--color-bg-tertiary);
    color: var(--color-text-primary);
}

.btn-secondary:hover:not(:disabled) {
    background: var(--color-border);
}

.btn-success {
    background: linear-gradient(135deg, var(--color-success), #059669);
    color: white;
}

.btn-danger {
    background: linear-gradient(135deg, var(--color-error), #dc2626);
    color: white;
}

.btn-ghost {
    background: transparent;
    color: var(--color-text-secondary);
}

.btn-ghost:hover {
    background: var(--color-bg-tertiary);
    color: var(--color-text-primary);
}

.btn-lg {
    padding: var(--space-4) var(--space-8);
    font-size: var(--font-size-base);
}

.btn-sm {
    padding: var(--space-2) var(--space-4);
    font-size: var(--font-size-xs);
}

.btn-icon {
    width: 40px;
    height: 40px;
    padding: 0;
    border-radius: var(--radius-md);
}

/* ==========================================
   FORMS
   ========================================== */
.form-group {
    margin-bottom: var(--space-5);
}

.form-label {
    display: block;
    font-size: var(--font-size-sm);
    font-weight: 500;
    color: var(--color-text-primary);
    margin-bottom: var(--space-2);
}

.form-input,
.form-select,
.form-textarea {
    width: 100%;
    padding: var(--space-3) var(--space-4);
    font-size: var(--font-size-base);
    font-family: inherit;
    color: var(--color-text-primary);
    background: var(--color-bg-secondary);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    transition: all var(--transition-fast);
}

.form-input:focus,
.form-select:focus,
.form-textarea:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(0, 102, 204, 0.1);
}

.form-textarea {
    min-height: 120px;
    resize: vertical;
}

.form-hint {
    font-size: var(--font-size-xs);
    color: var(--color-text-muted);
    margin-top: var(--space-1);
}

/* ==========================================
   TABLES
   ========================================== */
.table-container {
    overflow-x: auto;
    border-radius: var(--radius-lg);
    border: 1px solid var(--color-border);
}

.table {
    width: 100%;
    border-collapse: collapse;
    font-size: var(--font-size-sm);
}

.table th,
.table td {
    padding: var(--space-4);
    text-align: left;
    border-bottom: 1px solid var(--color-border);
}

.table th {
    background: var(--color-bg-tertiary);
    font-weight: 600;
    color: var(--color-text-primary);
}

.table tr:hover {
    background: var(--color-bg-tertiary);
}

.table tr:last-child td {
    border-bottom: none;
}

/* ==========================================
   BADGES
   ========================================== */
.badge {
    display: inline-flex;
    align-items: center;
    padding: var(--space-1) var(--space-3);
    font-size: var(--font-size-xs);
    font-weight: 500;
    border-radius: var(--radius-full);
}

.badge-success {
    background: rgba(16, 185, 129, 0.1);
    color: var(--color-success);
}

.badge-warning {
    background: rgba(245, 158, 11, 0.1);
    color: var(--color-warning);
}

.badge-error {
    background: rgba(239, 68, 68, 0.1);
    color: var(--color-error);
}

.badge-info {
    background: rgba(59, 130, 246, 0.1);
    color: var(--color-info);
}

/* ==========================================
   STAT CARDS
   ========================================== */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: var(--space-6);
    margin-bottom: var(--space-8);
}

.stat-card {
    background: var(--color-bg-secondary);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-xl);
    padding: var(--space-6);
}

.stat-card-icon {
    width: 48px;
    height: 48px;
    border-radius: var(--radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    margin-bottom: var(--space-4);
}

.stat-card-value {
    font-size: var(--font-size-3xl);
    font-weight: 700;
    color: var(--color-text-primary);
}

.stat-card-label {
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
}

/* ==========================================
   NAV & SIDEBAR
   ========================================== */
.nav-brand {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    margin-bottom: var(--space-8);
}

.nav-brand-logo {
    width: 40px;
    height: 40px;
    border-radius: var(--radius-lg);
    object-fit: contain;
}

.nav-brand-text {
    font-size: var(--font-size-lg);
    font-weight: 700;
    color: var(--color-text-primary);
}

.nav-section {
    margin-bottom: var(--space-6);
}

.nav-section-title {
    font-size: var(--font-size-xs);
    font-weight: 600;
    color: var(--color-text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: var(--space-3);
}

.nav-link {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    padding: var(--space-3) var(--space-4);
    border-radius: var(--radius-lg);
    color: var(--color-text-secondary);
    font-size: var(--font-size-sm);
    font-weight: 500;
    transition: all var(--transition-fast);
    margin-bottom: var(--space-1);
}

.nav-link:hover {
    background: var(--color-bg-tertiary);
    color: var(--color-text-primary);
}

.nav-link.active {
    background: var(--color-primary);
    color: white;
}

.nav-link-icon {
    font-size: 1.25rem;
    opacity: 0.8;
}

/* ==========================================
   UTILITIES
   ========================================== */
.flex { display: flex; }
.flex-col { flex-direction: column; }
.items-center { align-items: center; }
.justify-between { justify-content: space-between; }
.gap-2 { gap: var(--space-2); }
.gap-4 { gap: var(--space-4); }
.gap-6 { gap: var(--space-6); }

.text-center { text-align: center; }
.text-right { text-align: right; }
.text-muted { color: var(--color-text-muted); }
.text-success { color: var(--color-success); }
.text-warning { color: var(--color-warning); }
.text-error { color: var(--color-error); }

.mt-4 { margin-top: var(--space-4); }
.mt-6 { margin-top: var(--space-6); }
.mb-4 { margin-bottom: var(--space-4); }
.mb-6 { margin-bottom: var(--space-6); }

.hidden { display: none; }

/* ==========================================
   ANIMATIONS
   ========================================== */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

@keyframes slideIn {
    from { transform: translateX(-20px); opacity: 0; }
    to { transform: translateX(0); opacity: 1; }
}

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.5; }
}

.animate-fade-in {
    animation: fadeIn 0.3s ease forwards;
}

.animate-slide-in {
    animation: slideIn 0.3s ease forwards;
}

/* ==========================================
   RESPONSIVE
   ========================================== */
@media (max-width: 1024px) {
    .admin-layout {
        grid-template-columns: 1fr;
    }
    
    .admin-sidebar {
        position: fixed;
        left: -280px;
        z-index: 1000;
        transition: left var(--transition-base);
    }
    
    .admin-sidebar.open {
        left: 0;
    }
}

@media (max-width: 768px) {
    html {
        font-size: 14px;
    }
    
    .stats-grid {
        grid-template-columns: 1fr;
    }
    
    .admin-main {
        padding: var(--space-4);
    }
}

/* ==========================================
   SIDEBAR DROPDOWNS
   ========================================== */
.nav-dropdown {
    margin-bottom: var(--space-2);
}

.nav-dropdown-summary {
    display: flex;
    align-items: center;
    padding: var(--space-3) var(--space-4);
    font-size: var(--font-size-sm);
    font-weight: 600;
    color: var(--color-text-secondary);
    cursor: pointer;
    border-radius: var(--radius-lg);
    transition: all var(--transition-fast);
    list-style: none; /* remove default arrow */
}

/* Custom caret */
.nav-dropdown-summary::-webkit-details-marker {
    display: none;
}

.nav-dropdown-summary:hover {
    background: var(--color-bg-tertiary);
    color: var(--color-text-primary);
}

.nav-dropdown[open] .nav-dropdown-summary {
    color: var(--color-primary);
    margin-bottom: var(--space-2);
}

.nav-dropdown-content {
    display: flex;
    flex-direction: column;
    padding-left: var(--space-4);
    border-left: 2px solid var(--color-border);
    margin-left: var(--space-4);
    gap: var(--space-1);
    animation: fadeIn var(--transition-fast) ease-in-out;
}

.nav-dropdown-content .nav-link {
    margin-bottom: 0;
    font-size: 0.85rem;
    padding: var(--space-2) var(--space-3);
}