:root {
    /* Professional, muted palette */
    --primary-color: #2563eb;
    --primary-dark: #1e40af;
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-tertiary: #94a3b8;
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --border-color: #e2e8f0;
    --accent-color: #0ea5e9;
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --danger-color: #ef4444;
    
    /* Spacing & Layout */
    --border-radius: 8px;
    --border-radius-lg: 12px;
    --transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

* {
    box-sizing: border-box;
}

body {
    background: var(--bg-secondary);
    min-height: 100vh;
    font-family: -apple-system, BlinkMacSystemFont, 'Inter', 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    color: var(--text-primary);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Navigation */
.navbar {
    background: var(--bg-primary) !important;
    border-bottom: 1px solid var(--border-color);
    padding: 1.25rem 0;
    box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.05);
}

.navbar-brand {
    color: var(--text-primary) !important;
    font-weight: 700;
    font-size: 1.5rem;
    letter-spacing: -0.025em;
}

.nav-link {
    color: var(--text-secondary) !important;
    font-weight: 500;
    font-size: 0.95rem;
    transition: var(--transition);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.nav-link:hover {
    color: var(--text-primary) !important;
}

.nav-link i {
    width: 18px;
    height: 18px;
}

/* Main Content */
.main-content {
    padding-top: 3rem;
    padding-bottom: 3rem;
}

/* Hero Section */
.hero-section {
    padding: 5rem 0;
    max-width: 900px;
    margin: 0 auto;
}

.hero-section h1 {
    color: var(--text-primary);
    font-size: 3.5rem;
    font-weight: 800;
    letter-spacing: -0.03em;
    line-height: 1.1;
    margin-bottom: 1.5rem;
}

.hero-section .lead {
    font-size: 1.25rem;
    color: var(--text-secondary);
    line-height: 1.7;
    font-weight: 400;
    max-width: 700px;
    margin: 0 auto 3rem;
}

/* Feature Cards */
.features-grid {
    margin: 3rem 0;
}

.feature-card {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    padding: 2rem 1.5rem;
    text-align: center;
    transition: var(--transition);
    height: 100%;
}

.feature-card:hover {
    border-color: var(--primary-color);
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.1);
}

.feature-icon {
    width: 40px;
    height: 40px;
    margin-bottom: 1rem;
    color: var(--primary-color);
}

.feature-card h5 {
    color: var(--text-primary);
    margin-bottom: 0.75rem;
    font-weight: 600;
    font-size: 1.1rem;
}

.feature-card p {
    color: var(--text-secondary);
    font-size: 0.95rem;
    margin-bottom: 0;
    line-height: 1.6;
}

/* Buttons */
.btn-primary {
    background: var(--primary-color);
    border: none;
    border-radius: var(--border-radius);
    padding: 0.75rem 1.5rem;
    font-weight: 600;
    font-size: 0.95rem;
    transition: var(--transition);
    color: white;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
}

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
}

.btn-primary:active {
    transform: translateY(0);
}

.btn-primary i {
    width: 18px;
    height: 18px;
}

.btn-lg {
    padding: 1rem 2rem;
    font-size: 1rem;
}

.btn-outline-primary {
    background: transparent;
    border: 1px solid var(--border-color);
    color: var(--text-primary);
}

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

/* Dashboard */
.dashboard-header h2 {
    color: var(--text-primary);
    font-weight: 700;
    font-size: 2rem;
    letter-spacing: -0.025em;
    margin-bottom: 0.5rem;
}

.dashboard-header p {
    color: var(--text-secondary);
    font-size: 1rem;
}

/* Cards */
.card {
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    background: var(--bg-primary);
    box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.05);
    transition: var(--transition);
}

.card:hover {
    box-shadow: 0 4px 12px 0 rgba(0, 0, 0, 0.08);
}

.card-title {
    color: var(--text-primary);
    font-weight: 600;
    font-size: 1.1rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.card-title i {
    width: 20px;
    height: 20px;
    color: var(--text-tertiary);
}

/* Form Elements */
.form-select {
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    transition: var(--transition);
    font-size: 0.95rem;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    padding: 0.625rem 0.875rem;
}

.form-select:focus {
    border-color: var(--primary-color);
    outline: none;
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

/* Video Cards */
.video-card {
    background: var(--bg-primary);
    border-radius: var(--border-radius-lg);
    overflow: hidden;
    transition: var(--transition);
    border: 1px solid var(--border-color);
    height: 100%;
    cursor: pointer;
}

.video-card:hover {
    border-color: var(--primary-color);
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.12);
}

.video-thumbnail {
    position: relative;
    overflow: hidden;
    aspect-ratio: 16/9;
    background: var(--bg-tertiary);
}

.video-thumbnail img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: var(--transition);
}

.video-card:hover .video-thumbnail img {
    transform: scale(1.02);
}

.video-overlay {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background: rgba(15, 23, 42, 0.8);
    backdrop-filter: blur(4px);
    border-radius: 50%;
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    transition: var(--transition);
}

.video-card:hover .video-overlay {
    opacity: 1;
}

.play-icon {
    color: white;
    width: 20px;
    height: 20px;
}

.video-info {
    padding: 1rem;
}

.video-title {
    font-size: 0.95rem;
    font-weight: 600;
    line-height: 1.4;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.video-info small {
    color: var(--text-tertiary);
    font-size: 0.85rem;
}

/* Checkboxes */
.form-check-input {
    width: 1.125rem;
    height: 1.125rem;
    border-radius: 4px;
    border: 1.5px solid var(--border-color);
    transition: var(--transition);
    cursor: pointer;
}

.form-check-input:checked {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
}

.form-check-input:focus {
    outline: none;
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.form-check-label {
    cursor: pointer;
    user-select: none;
}

/* Alerts */
.alert {
    border: 1px solid transparent;
    border-radius: var(--border-radius);
    font-weight: 500;
    font-size: 0.95rem;
}

.alert-success {
    background: #f0fdf4;
    border-color: #86efac;
    color: #15803d;
}

.alert-danger {
    background: #fef2f2;
    border-color: #fca5a5;
    color: #b91c1c;
}

.alert-warning {
    background: #fffbeb;
    border-color: #fcd34d;
    color: #b45309;
}

.alert-info {
    background: #eff6ff;
    border-color: #93c5fd;
    color: #1e40af;
}

/* Loading States */
.spinner-border {
    width: 2.5rem;
    height: 2.5rem;
    border-width: 3px;
}

/* Modal */
.modal-content {
    border: none;
    border-radius: var(--border-radius-lg);
    box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
}

.modal-body {
    padding: 2rem;
}

.modal-body h5 {
    color: var(--text-primary);
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.modal-body p {
    color: var(--text-secondary);
}

/* Responsive Design */
@media (max-width: 768px) {
    .hero-section {
        padding: 3rem 0;
    }
    
    .hero-section h1 {
        font-size: 2.5rem;
    }
    
    .hero-section .lead {
        font-size: 1.1rem;
    }
    
    .feature-card {
        margin-bottom: 1rem;
    }
    
    .btn-lg {
        padding: 0.875rem 1.5rem;
        font-size: 0.95rem;
    }
    
    .dashboard-header h2 {
        font-size: 1.75rem;
    }
}

/* Utility Classes */
.text-muted {
    color: var(--text-secondary) !important;
}

.text-tertiary {
    color: var(--text-tertiary) !important;
}

/* Subtle animations */
@media (prefers-reduced-motion: no-preference) {
    .fade-in {
        animation: fadeIn 0.3s ease-out;
    }
    
    @keyframes fadeIn {
        from {
            opacity: 0;
            transform: translateY(8px);
        }
        to {
            opacity: 1;
            transform: translateY(0);
        }
    }
}