/* =====================================================
   EDUHUB - GLOBAL STYLESHEET
   Professional Modern Design System
   ===================================================== */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&display=swap');

/* ===== CSS VARIABLES (Design Tokens) ===== */
:root {
    /* Primary Colors */
    --primary: #2563EB;
    --primary-hover: #1D4ED8;
    --primary-light: #EFF6FF;
    --primary-gradient: linear-gradient(135deg, #2563EB 0%, #1D4ED8 100%);

    /* Secondary Colors */
    --success: #10B981;
    --success-hover: #059669;
    --success-light: #ECFDF5;

    /* Danger/Warning */
    --danger: #EF4444;
    --danger-hover: #DC2626;
    --danger-light: #FEE2E2;

    --warning: #F59E0B;
    --warning-hover: #D97706;
    --warning-light: #FEF3C7;

    /* Neutral Colors */
    --dark: #1F2937;
    --gray: #6B7280;
    --gray-light: #9CA3AF;
    --border: #E5E7EB;
    --bg: #F9FAFB;
    --white: #FFFFFF;

    /* Gradients */
    --hero-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --purple-gradient: linear-gradient(135deg, #8B5CF6 0%, #7C3AED 100%);
    --glass-bg: rgba(255, 255, 255, 0.8);

    /* Shadows */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px rgba(0, 0, 0, 0.15);

    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;

    /* Border Radius */
    --radius-sm: 4px;
    --radius: 8px;
    --radius-lg: 12px;
    --radius-xl: 16px;
    --radius-full: 9999px;

    /* Transitions */
    --transition: all 0.3s ease;
    --transition-fast: all 0.15s ease;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family);
    font-size: 14px;
    line-height: 1.6;
    color: var(--dark);
    background: var(--bg);
    -webkit-font-smoothing: antialiased;
}

/* ===== TYPOGRAPHY ===== */
h1,
h2,
h3,
h4,
h5,
h6 {
    font-weight: 700;
    line-height: 1.2;
    color: var(--dark);
}

h1 {
    font-size: 32px;
}

h2 {
    font-size: 24px;
}

h3 {
    font-size: 20px;
}

h4 {
    font-size: 18px;
}

h5 {
    font-size: 16px;
}

h6 {
    font-size: 14px;
}

p {
    margin-bottom: 16px;
}

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

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

/* ===== BUTTONS ===== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px 24px;
    font-size: 14px;
    font-weight: 600;
    font-family: var(--font-family);
    border: none;
    border-radius: var(--radius);
    cursor: pointer;
    transition: var(--transition);
    text-decoration: none;
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

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

.btn-primary:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 8px 20px rgba(37, 99, 235, 0.4);
}

.btn-success {
    background: linear-gradient(135deg, var(--success) 0%, var(--success-hover) 100%);
    color: var(--white);
}

.btn-success:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 8px 20px rgba(16, 185, 129, 0.4);
}

.btn-danger {
    background: linear-gradient(135deg, var(--danger) 0%, var(--danger-hover) 100%);
    color: var(--white);
}

.btn-secondary {
    background: var(--border);
    color: var(--gray);
}

.btn-secondary:hover {
    background: #D1D5DB;
}

.btn-outline {
    background: transparent;
    border: 2px solid var(--primary);
    color: var(--primary);
}

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

.btn-sm {
    padding: 8px 16px;
    font-size: 13px;
}

.btn-lg {
    padding: 16px 32px;
    font-size: 16px;
}

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

/* ===== CARDS ===== */
.card {
    background: var(--white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    overflow: hidden;
    transition: var(--transition);
}

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

.card-header {
    padding: 20px 24px;
    border-bottom: 1px solid var(--border);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.card-body {
    padding: 24px;
}

.card-footer {
    padding: 16px 24px;
    border-top: 1px solid var(--border);
    background: var(--bg);
}

/* ===== GLASSMORPHISM CARD ===== */
.glass-card {
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.3);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-lg);
}

/* ===== FORMS ===== */
.form-group {
    margin-bottom: 20px;
}

.form-label {
    display: block;
    font-size: 14px;
    font-weight: 600;
    color: var(--dark);
    margin-bottom: 8px;
}

.form-control {
    width: 100%;
    padding: 12px 16px;
    font-size: 14px;
    font-family: var(--font-family);
    color: var(--dark);
    background: var(--white);
    border: 2px solid var(--border);
    border-radius: var(--radius);
    transition: var(--transition);
}

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

.form-control::placeholder {
    color: var(--gray-light);
}

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

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

select.form-control {
    cursor: pointer;
}

/* ===== BADGES ===== */
.badge {
    display: inline-flex;
    align-items: center;
    padding: 4px 12px;
    font-size: 12px;
    font-weight: 600;
    border-radius: var(--radius-full);
}

.badge-primary {
    background: var(--primary-light);
    color: var(--primary);
}

.badge-success {
    background: var(--success-light);
    color: var(--success);
}

.badge-danger {
    background: var(--danger-light);
    color: var(--danger);
}

.badge-warning {
    background: var(--warning-light);
    color: var(--warning);
}

.badge-gray {
    background: var(--border);
    color: var(--gray);
}

/* ===== ALERTS ===== */
.alert {
    padding: 16px 20px;
    border-radius: var(--radius);
    font-size: 14px;
    font-weight: 500;
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 20px;
}

.alert-success {
    background: var(--success-light);
    color: var(--success-hover);
    border: 1px solid var(--success);
}

.alert-danger {
    background: var(--danger-light);
    color: var(--danger-hover);
    border: 1px solid var(--danger);
}

.alert-warning {
    background: var(--warning-light);
    color: var(--warning-hover);
    border: 1px solid var(--warning);
}

.alert-info {
    background: var(--primary-light);
    color: var(--primary);
    border: 1px solid var(--primary);
}

/* ===== TABLES ===== */
.table {
    width: 100%;
    border-collapse: collapse;
}

.table th,
.table td {
    padding: 14px 16px;
    text-align: left;
    border-bottom: 1px solid var(--border);
}

.table th {
    font-weight: 600;
    font-size: 12px;
    text-transform: uppercase;
    color: var(--gray);
    background: var(--bg);
}

.table tbody tr {
    transition: var(--transition-fast);
}

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

/* ===== PROGRESS BAR ===== */
.progress {
    width: 100%;
    height: 8px;
    background: var(--border);
    border-radius: var(--radius-full);
    overflow: hidden;
}

.progress-bar {
    height: 100%;
    background: var(--primary-gradient);
    border-radius: var(--radius-full);
    transition: width 0.5s ease;
}

.progress-bar.success {
    background: linear-gradient(90deg, var(--success) 0%, var(--success-hover) 100%);
}

/* ===== AVATAR ===== */
.avatar {
    width: 40px;
    height: 40px;
    border-radius: var(--radius-full);
    object-fit: cover;
    border: 2px solid var(--border);
}

.avatar-sm {
    width: 32px;
    height: 32px;
}

.avatar-lg {
    width: 56px;
    height: 56px;
}

.avatar-xl {
    width: 80px;
    height: 80px;
}

/* ===== TOAST / NOTIFICATION ===== */
.toast-container {
    position: fixed;
    top: 20px;
    right: 20px;
    z-index: 9999;
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.toast {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 16px 20px;
    background: var(--white);
    border-radius: var(--radius);
    box-shadow: var(--shadow-lg);
    min-width: 300px;
    animation: slideIn 0.3s ease;
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateX(100px);
    }

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

.toast.success {
    border-left: 4px solid var(--success);
}

.toast.error {
    border-left: 4px solid var(--danger);
}

.toast.warning {
    border-left: 4px solid var(--warning);
}

/* ===== LOADING SPINNER ===== */
.spinner {
    width: 20px;
    height: 20px;
    border: 2px solid var(--border);
    border-top-color: var(--primary);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

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

.spinner-lg {
    width: 40px;
    height: 40px;
    border-width: 3px;
}

/* ===== SKELETON LOADING ===== */
.skeleton {
    background: linear-gradient(90deg, var(--border) 25%, #E8EAED 50%, var(--border) 75%);
    background-size: 200% 100%;
    animation: skeleton-loading 1.5s infinite;
    border-radius: var(--radius);
}

@keyframes skeleton-loading {
    0% {
        background-position: 200% 0;
    }

    100% {
        background-position: -200% 0;
    }
}

.skeleton-text {
    height: 16px;
    margin-bottom: 8px;
}

.skeleton-title {
    height: 24px;
    width: 60%;
    margin-bottom: 12px;
}

.skeleton-img {
    width: 100%;
    height: 200px;
}

/* ===== EMPTY STATE ===== */
.empty-state {
    text-align: center;
    padding: 60px 20px;
    color: var(--gray-light);
}

.empty-state i {
    font-size: 64px;
    margin-bottom: 20px;
    opacity: 0.5;
}

.empty-state h3 {
    font-size: 20px;
    color: var(--gray);
    margin-bottom: 8px;
}

.empty-state p {
    margin-bottom: 24px;
}

/* ===== RATING STARS ===== */
.rating {
    display: inline-flex;
    gap: 4px;
}

.rating i {
    color: var(--warning);
}

.rating i.empty {
    color: var(--border);
}

/* ===== PRICE TAG ===== */
.price {
    font-size: 24px;
    font-weight: 700;
    color: var(--dark);
}

.price .currency {
    font-size: 16px;
    font-weight: 600;
}

.price.free {
    color: var(--success);
}

.price-old {
    font-size: 16px;
    color: var(--gray-light);
    text-decoration: line-through;
    margin-right: 8px;
}

/* ===== UTILITY CLASSES ===== */
.text-center {
    text-align: center;
}

.text-right {
    text-align: right;
}

.text-primary {
    color: var(--primary);
}

.text-success {
    color: var(--success);
}

.text-danger {
    color: var(--danger);
}

.text-gray {
    color: var(--gray);
}

.text-muted {
    color: var(--gray-light);
}

.font-bold {
    font-weight: 700;
}

.font-semibold {
    font-weight: 600;
}

.font-medium {
    font-weight: 500;
}

.mb-0 {
    margin-bottom: 0;
}

.mb-1 {
    margin-bottom: 8px;
}

.mb-2 {
    margin-bottom: 16px;
}

.mb-3 {
    margin-bottom: 24px;
}

.mb-4 {
    margin-bottom: 32px;
}

.mt-1 {
    margin-top: 8px;
}

.mt-2 {
    margin-top: 16px;
}

.mt-3 {
    margin-top: 24px;
}

.mt-4 {
    margin-top: 32px;
}

.p-1 {
    padding: 8px;
}

.p-2 {
    padding: 16px;
}

.p-3 {
    padding: 24px;
}

.p-4 {
    padding: 32px;
}

.d-flex {
    display: flex;
}

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

.align-center {
    align-items: center;
}

.justify-between {
    justify-content: space-between;
}

.justify-center {
    justify-content: center;
}

.gap-1 {
    gap: 8px;
}

.gap-2 {
    gap: 16px;
}

.gap-3 {
    gap: 24px;
}

.w-100 {
    width: 100%;
}

.h-100 {
    height: 100%;
}

.rounded {
    border-radius: var(--radius);
}

.rounded-lg {
    border-radius: var(--radius-lg);
}

.rounded-full {
    border-radius: var(--radius-full);
}

.shadow {
    box-shadow: var(--shadow);
}

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

/* ===== GRID SYSTEM ===== */
.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

.row {
    display: flex;
    flex-wrap: wrap;
    margin: 0 -12px;
}

.col {
    flex: 1;
    padding: 0 12px;
}

.col-12 {
    width: 100%;
}

.col-6 {
    width: 50%;
}

.col-4 {
    width: 33.333%;
}

.col-3 {
    width: 25%;
}

/* ===== COURSE CARD ===== */
.course-card {
    background: var(--white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    overflow: hidden;
    transition: var(--transition);
}

.course-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-xl);
}

.course-card .thumbnail {
    width: 100%;
    height: 180px;
    object-fit: cover;
    position: relative;
}

.course-card .thumbnail img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.course-card .content {
    padding: 20px;
}

.course-card .category {
    font-size: 12px;
    font-weight: 600;
    color: var(--primary);
    text-transform: uppercase;
    margin-bottom: 8px;
}

.course-card .title {
    font-size: 18px;
    font-weight: 700;
    color: var(--dark);
    margin-bottom: 8px;
    line-height: 1.3;
}

.course-card .teacher {
    font-size: 13px;
    color: var(--gray);
    margin-bottom: 12px;
}

.course-card .meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: 16px;
    border-top: 1px solid var(--border);
}

/* ===== RESPONSIVE ===== */
@media (max-width: 1024px) {
    .col-4 {
        width: 50%;
    }

    .col-3 {
        width: 50%;
    }
}

@media (max-width: 768px) {
    h1 {
        font-size: 26px;
    }

    h2 {
        font-size: 22px;
    }

    .container {
        padding: 0 16px;
    }

    .col-6,
    .col-4,
    .col-3 {
        width: 100%;
    }

    .btn {
        padding: 10px 20px;
    }
}

@media (max-width: 480px) {
    h1 {
        font-size: 22px;
    }

    .card-header,
    .card-body,
    .card-footer {
        padding: 16px;
    }
}