:root {
    --bg-color: #0f172a;
    --card-bg: rgba(30, 41, 59, 0.7);
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --accent-gradient: linear-gradient(135deg, #6366f1 0%, #a855f7 100%);
    --accent-color: #8b5cf6;
    --success-color: #10b981;
    --error-color: #ef4444;
    --glass-border: 1px solid rgba(255, 255, 255, 0.1);
    --radius: 12px;
    --input-bg: rgba(15, 23, 42, 0.5);
    --input-text: white;
    --alert-bg: rgba(239, 68, 68, 0.1);
    --alert-text: #fca5a5;
}

body.light-mode {
    --bg-color: #f1f5f9;
    --card-bg: rgba(255, 255, 255, 0.8);
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --glass-border: 1px solid rgba(0, 0, 0, 0.1);
    --input-bg: rgba(255, 255, 255, 0.9);
    --input-text: #1e293b;
    --alert-bg: rgba(239, 68, 68, 0.1);
    --alert-text: #b91c1c;
}

.menu-toggle {
    display: none;
    background: transparent;
    border: none;
    color: var(--text-primary);
    font-size: 1.5rem;
    cursor: pointer;
    padding: 0.5rem;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

a {
    text-decoration: none;
    color: inherit;
}

/* Utilities */
.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

.btn {
    display: inline-block;
    padding: 12px 24px;
    background: var(--accent-gradient);
    color: white;
    border-radius: var(--radius);
    border: none;
    cursor: pointer;
    font-weight: 600;
    transition: transform 0.2s, opacity 0.2s;
}

.btn:hover {
    transform: translateY(-2px);
    opacity: 0.9;
}

.btn-secondary {
    background: transparent;
    border: var(--glass-border);
    color: var(--text-primary);
}

.btn-google {
    background: white;
    color: #444;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    margin-top: 1rem;
    border: none;
}

.btn-google:hover {
    background: #f1f1f1;
}

.btn-google img {
    width: 20px;
}

.divider {
    display: flex;
    align-items: center;
    text-align: center;
    margin: 1.5rem 0;
    color: var(--text-secondary);
    font-size: 0.8rem;
}

.divider::before,
.divider::after {
    content: '';
    flex: 1;
    border-bottom: 1px solid var(--text-secondary);
    opacity: 0.2;
}

.divider:not(:empty)::before {
    margin-right: .5em;
}

.divider:not(:empty)::after {
    margin-left: .5em;
}

.glass-panel {
    background: var(--card-bg);
    backdrop-filter: blur(12px);
    border: var(--glass-border);
    border-radius: var(--radius);
    padding: 2rem;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    color: var(--text-primary);
}

/* Auth Pages */
.auth-container {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: radial-gradient(circle at 50% 50%, var(--bg-color) 0%, #000 100%);
}

.auth-box {
    width: 100%;
    max-width: 400px;
}

.auth-header {
    text-align: center;
    margin-bottom: 2rem;
}

.auth-header h1 {
    font-size: 2rem;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
    margin-bottom: 0.5rem;
}

.form-group {
    margin-bottom: 1.5rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.form-control {
    width: 100%;
    padding: 12px;
    background: var(--input-bg);
    border: var(--glass-border);
    border-radius: var(--radius);
    color: var(--input-text);
    font-size: 1rem;
    transition: border-color 0.2s;
}

.form-control:focus {
    outline: none;
    border-color: var(--accent-color);
}

/* Dashboard */
.nav-header {
    background: var(--card-bg);
    border-bottom: var(--glass-border);
    padding: 1rem 0;
    margin-bottom: 2rem;
}

.nav-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 1rem;
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.nav-brand {
    display: flex;
    align-items: center;
    justify-content: space-between;
    width: auto;
}

.nav-menu {
    display: flex;
    flex-grow: 1;
    align-items: center;
    justify-content: space-between;
}

.info-box {
    text-align: center;
    max-width: 600px;
    margin: 4rem auto;
}

.logo {
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--text-primary);
}

.subject-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 20px;
}

.subject-card {
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
    padding: 3rem 2rem;
    transition: transform 0.3s;
    cursor: pointer;
}

.subject-card:hover {
    transform: translateY(-5px);
    background: rgba(45, 55, 75, 0.8);
}

.subject-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
    color: var(--accent-color);
}

/* Lessons */
.lesson-list {
    margin-top: 2rem;
}

.lesson-item {
    display: flex;
    align-items: center;
    padding: 1.5rem;
    margin-bottom: 1rem;
    background: rgba(30, 41, 59, 0.4);
    border-radius: var(--radius);
    border: var(--glass-border);
    transition: background 0.2s;
}

.lesson-item:hover {
    background: rgba(30, 41, 59, 0.7);
}

.lesson-number {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--text-secondary);
    margin-right: 1.5rem;
    width: 30px;
}

.lesson-info {
    flex-grow: 1;
}

.lesson-title {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 0.25rem;
}

/* Video Player */
.video-container {
    width: 100%;
    margin-bottom: 2rem;
    border-radius: var(--radius);
    overflow: hidden;
    background: black;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
}

video {
    width: 100%;
    display: block;
}

.resources {
    margin-top: 2rem;
}

.resource-link {
    display: flex;
    align-items: center;
    padding: 1rem;
    background: rgba(30, 41, 59, 0.5);
    border-radius: var(--radius);
    margin-bottom: 0.5rem;
}

.resource-link i {
    margin-right: 10px;
    color: var(--accent-color);
}

.alert {
    padding: 1rem;
    border-radius: var(--radius);
    background: var(--alert-bg);
    color: var(--alert-text);
    border: 1px solid var(--alert-bg);
    margin-bottom: 1rem;
    text-align: center;
}

/* Responsive Design */
@media (max-width: 768px) {
    .container {
        padding: 0 1rem;
    }

    .nav-content {
        flex-direction: column;
        gap: 0;
        align-items: stretch;
    }

    .nav-brand {
        display: flex;
        justify-content: space-between;
        align-items: center;
        width: 100%;
        padding: 0.5rem 0;
    }

    .menu-toggle {
        display: block;
    }

    .nav-menu {
        display: none;
        flex-direction: column;
        width: 100%;
        gap: 1rem;
        padding-top: 1rem;
        border-top: var(--glass-border);
        margin-top: 0.5rem;
    }

    .nav-menu.active {
        display: flex;
    }

    .search-form {
        width: 100%;
        max-width: none !important;
        margin: 0 !important;
    }

    .nav-actions {
        flex-direction: column;
        width: 100%;
        gap: 0.5rem;
    }

    .nav-actions .btn {
        width: 100%;
        justify-content: flex-start;
    }

    .nav-text {
        display: inline;
        /* Ensure text is visible on mobile */
    }

    .nav-content .logo {
        margin-bottom: 0.5rem;
    }

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

    .auth-box {
        padding: 1rem;
    }

    .glass-panel {
        padding: 1.5rem;
    }

    .subject-card {
        padding: 2rem 1.5rem;
    }

    .lesson-item {
        padding: 1rem;
    }

    .lesson-number {
        margin-right: 1rem;
        font-size: 1rem;
    }

    .lesson-title {
        font-size: 1rem;
    }

    .admin-grid {
        grid-template-columns: 1fr !important;
    }

    /* Table Responsiveness */
    table {
        display: block;
        overflow-x: auto;
        white-space: nowrap;
    }
}

@media (max-width: 480px) {
    .auth-header h1 {
        font-size: 1.75rem;
    }

    .btn {
        width: 100%;
        text-align: center;
    }

    .nav-actions {
        flex-direction: column;
        width: 100%;
        gap: 0.5rem;
    }

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

    .info-box {
        margin: 2rem auto;
    }
}/* Tabs */
.tab-nav {
    display: flex;
    gap: 1rem;
    margin-bottom: 2rem;
    overflow-x: auto;
    padding-bottom: 0.5rem;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.tab-btn {
    padding: 10px 20px;
    background: transparent;
    border: none;
    color: var(--text-secondary);
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    border-radius: var(--radius);
    transition: all 0.2s;
    white-space: nowrap;
}

.tab-btn:hover {
    color: var(--text-primary);
    background: rgba(255, 255, 255, 0.05);
}

.tab-btn.active {
    color: white;
    background: var(--accent-gradient);
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
}

.tab-content {
    display: none;
    animation: fadeIn 0.3s ease;
}

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

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Mobile responsive for tabs */
@media (max-width: 768px) {
    .tab-nav {
        gap: 0.5rem;
    }

    .tab-btn {
        padding: 8px 16px;
        font-size: 0.85rem;
    }
}