/**
 * DADE Learn - Premium Design System
 * A modern, Coursera/Udemy-inspired design system
 * 
 * Table of Contents:
 * 1. CSS Variables (Colors, Typography, Spacing)
 * 2. Reset & Base Styles
 * 3. Typography
 * 4. Layout Utilities
 * 5. Buttons
 * 6. Forms
 * 7. Cards
 * 8. Navigation
 * 9. Alerts & Messages
 * 10. Animations
 */

/* ============================================================================
   1. CSS VARIABLES
   ============================================================================ */

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

:root {
    /* === Brand Colors === */
    --primary: #005f73;
    --primary-light: #0a9396;
    --primary-dark: #003f4f;
    --primary-50: rgba(0, 95, 115, 0.05);
    --primary-100: rgba(0, 95, 115, 0.1);

    --accent: #ffb703;
    --accent-light: #ffd166;
    --accent-dark: #e09600;

    /* === Semantic Colors === */
    --success: #10b981;
    --success-bg: #d1fae5;
    --warning: #f59e0b;
    --warning-bg: #fef3c7;
    --error: #ef4444;
    --error-bg: #fee2e2;
    --info: #3b82f6;
    --info-bg: #dbeafe;

    /* === Neutral Colors === */
    --white: #ffffff;
    --gray-50: #f8fafc;
    --gray-100: #f1f5f9;
    --gray-200: #e2e8f0;
    --gray-300: #cbd5e1;
    --gray-400: #94a3b8;
    --gray-500: #64748b;
    --gray-600: #475569;
    --gray-700: #334155;
    --gray-800: #1e293b;
    --gray-900: #0f172a;

    /* === Background Colors === */
    --bg-primary: var(--gray-50);
    --bg-secondary: var(--white);
    --bg-tertiary: var(--gray-100);

    /* === Text Colors === */
    --text-primary: var(--gray-800);
    --text-secondary: var(--gray-600);
    --text-muted: var(--gray-500);
    --text-light: var(--white);

    /* === Typography === */
    --font-primary: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-heading: 'Poppins', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;

    --text-xs: 0.75rem;
    --text-sm: 0.875rem;
    --text-base: 1rem;
    --text-lg: 1.125rem;
    --text-xl: 1.25rem;
    --text-2xl: 1.5rem;
    --text-3xl: 1.875rem;
    --text-4xl: 2.25rem;
    --text-5xl: 3rem;
    --text-6xl: 3.75rem;

    /* === 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;
    --space-20: 5rem;
    --space-24: 6rem;

    /* === 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-xs: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-sm: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px -1px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 8px 10px -6px rgba(0, 0, 0, 0.1);
    --shadow-2xl: 0 25px 50px -12px rgba(0, 0, 0, 0.25);
    --shadow-primary: 0 10px 30px -5px rgba(0, 95, 115, 0.3);
    --shadow-accent: 0 10px 30px -5px rgba(255, 183, 3, 0.3);

    /* === Transitions === */
    --transition-fast: 150ms ease;
    --transition-normal: 200ms ease;
    --transition-slow: 300ms ease;

    /* === Z-Index === */
    --z-dropdown: 100;
    --z-sticky: 200;
    --z-fixed: 300;
    --z-modal-backdrop: 400;
    --z-modal: 500;
    --z-tooltip: 600;

    /* === Container === */
    --container-sm: 640px;
    --container-md: 768px;
    --container-lg: 1024px;
    --container-xl: 1280px;
    --container-2xl: 1400px;

    /* === Header === */
    --header-height: 72px;
}

/* ============================================================================
   2. RESET & BASE STYLES
   ============================================================================ */

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

html {
    font-size: 16px;
    scroll-behavior: smooth;
    -webkit-text-size-adjust: 100%;
}

body {
    font-family: var(--font-primary);
    font-size: var(--text-base);
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-primary);
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

img,
video {
    max-width: 100%;
    height: auto;
    display: block;
}

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

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

ul,
ol {
    list-style: none;
}

button {
    font-family: inherit;
    cursor: pointer;
    border: none;
    background: none;
}

input,
textarea,
select {
    font-family: inherit;
    font-size: inherit;
}

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

/* ============================================================================
   3. TYPOGRAPHY
   ============================================================================ */

h1,
h2,
h3,
h4,
h5,
h6 {
    font-family: var(--font-heading);
    font-weight: 700;
    line-height: 1.25;
    color: var(--text-primary);
    margin-bottom: var(--space-4);
}

h1 {
    font-size: var(--text-5xl);
}

h2 {
    font-size: var(--text-4xl);
}

h3 {
    font-size: var(--text-3xl);
}

h4 {
    font-size: var(--text-2xl);
}

h5 {
    font-size: var(--text-xl);
}

h6 {
    font-size: var(--text-lg);
}

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

.text-gradient {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

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

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

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

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

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

/* ============================================================================
   4. LAYOUT UTILITIES
   ============================================================================ */

.container {
    width: 100%;
    max-width: var(--container-xl);
    margin: 0 auto;
    padding: 0 var(--space-4);
}

.container-sm {
    max-width: var(--container-sm);
}

.container-md {
    max-width: var(--container-md);
}

.container-lg {
    max-width: var(--container-lg);
}

.container-xl {
    max-width: var(--container-xl);
}

.container-2xl {
    max-width: var(--container-2xl);
}

.flex {
    display: flex;
}

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

.flex-wrap {
    flex-wrap: wrap;
}

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

.items-start {
    align-items: flex-start;
}

.items-end {
    align-items: flex-end;
}

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

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

.justify-end {
    justify-content: flex-end;
}

.gap-1 {
    gap: var(--space-1);
}

.gap-2 {
    gap: var(--space-2);
}

.gap-3 {
    gap: var(--space-3);
}

.gap-4 {
    gap: var(--space-4);
}

.gap-6 {
    gap: var(--space-6);
}

.gap-8 {
    gap: var(--space-8);
}

.grid {
    display: grid;
}

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

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

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

.section {
    padding: var(--space-20) 0;
}

.section-sm {
    padding: var(--space-12) 0;
}

.section-lg {
    padding: var(--space-24) 0;
}

/* ============================================================================
   5. BUTTONS
   ============================================================================ */

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-2);
    padding: var(--space-3) var(--space-6);
    font-size: var(--text-base);
    font-weight: 600;
    line-height: 1.5;
    border-radius: var(--radius-lg);
    transition: all var(--transition-normal);
    cursor: pointer;
    white-space: nowrap;
    text-decoration: none;
}

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

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

.btn-primary {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 100%);
    color: var(--white);
    box-shadow: var(--shadow-sm);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-primary);
    color: var(--white);
}

.btn-accent {
    background: linear-gradient(135deg, var(--accent) 0%, var(--accent-light) 100%);
    color: var(--gray-900);
    box-shadow: var(--shadow-sm);
}

.btn-accent:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-accent);
    color: var(--gray-900);
}

.btn-secondary {
    background: var(--gray-100);
    color: var(--text-primary);
}

.btn-secondary:hover {
    background: var(--gray-200);
    color: var(--text-primary);
}

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

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

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

.btn-white:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
    color: var(--primary);
}

.btn-icon {
    width: 44px;
    height: 44px;
    padding: 0;
    border-radius: var(--radius-full);
}

.btn-block {
    width: 100%;
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none !important;
}

/* ============================================================================
   6. FORMS
   ============================================================================ */

.form-group {
    margin-bottom: var(--space-5);
}

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

.form-input,
.form-textarea,
.form-select {
    width: 100%;
    padding: var(--space-3) var(--space-4);
    font-size: var(--text-base);
    color: var(--text-primary);
    background-color: var(--white);
    border: 2px solid var(--gray-200);
    border-radius: var(--radius-lg);
    transition: all var(--transition-fast);
}

.form-input:focus,
.form-textarea:focus,
.form-select:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px var(--primary-100);
}

.form-input::placeholder,
.form-textarea::placeholder {
    color: var(--gray-400);
}

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

.form-input.error,
.form-textarea.error {
    border-color: var(--error);
}

.form-error {
    display: block;
    margin-top: var(--space-2);
    font-size: var(--text-sm);
    color: var(--error);
}

.form-hint {
    display: block;
    margin-top: var(--space-2);
    font-size: var(--text-sm);
    color: var(--text-muted);
}

/* Floating Labels */
.form-floating {
    position: relative;
}

.form-floating .form-input {
    padding-top: var(--space-6);
}

.form-floating .form-label {
    position: absolute;
    top: 50%;
    left: var(--space-4);
    transform: translateY(-50%);
    color: var(--gray-400);
    transition: all var(--transition-fast);
    pointer-events: none;
    margin: 0;
}

.form-floating .form-input:focus+.form-label,
.form-floating .form-input:not(:placeholder-shown)+.form-label {
    top: var(--space-2);
    transform: translateY(0);
    font-size: var(--text-xs);
    color: var(--primary);
}

/* ============================================================================
   7. CARDS
   ============================================================================ */

.card {
    background: var(--white);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-sm);
    overflow: hidden;
    transition: all var(--transition-normal);
}

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

.card-body {
    padding: var(--space-5);
}

.card-footer {
    padding: var(--space-4) var(--space-5);
    background: var(--gray-50);
    border-top: 1px solid var(--gray-100);
}

/* Course Card */
.course-card {
    display: flex;
    flex-direction: column;
    height: 100%;
    border: 1px solid var(--gray-100);
}

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

.course-card .card-image {
    position: relative;
    aspect-ratio: 16/9;
    overflow: hidden;
}

.course-card .card-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform var(--transition-slow);
}

.course-card:hover .card-image img {
    transform: scale(1.05);
}

.course-card .card-badge {
    position: absolute;
    top: var(--space-3);
    left: var(--space-3);
    padding: var(--space-1) var(--space-3);
    font-size: var(--text-xs);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    background: var(--accent);
    color: var(--gray-900);
    border-radius: var(--radius-full);
}

.course-card .card-body {
    flex: 1;
    display: flex;
    flex-direction: column;
}

.course-card .card-meta {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    margin-bottom: var(--space-2);
    font-size: var(--text-sm);
    color: var(--text-muted);
}

.course-card .card-title {
    font-size: var(--text-lg);
    font-weight: 600;
    margin-bottom: var(--space-2);
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.course-card .card-title a {
    color: var(--text-primary);
}

.course-card .card-title a:hover {
    color: var(--primary);
}

.course-card .card-excerpt {
    font-size: var(--text-sm);
    color: var(--text-secondary);
    margin-bottom: var(--space-4);
    flex: 1;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.course-card .card-footer {
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.course-card .card-rating {
    display: flex;
    align-items: center;
    gap: var(--space-1);
}

.course-card .card-rating .stars {
    color: var(--accent);
}

.course-card .card-rating .rating-num {
    font-weight: 600;
    color: var(--text-primary);
}

.course-card .card-rating .rating-count {
    color: var(--text-muted);
    font-size: var(--text-sm);
}

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

/* ============================================================================
   8. NAVIGATION
   ============================================================================ */

.header {
    position: sticky;
    top: 0;
    z-index: var(--z-sticky);
    background: var(--white);
    box-shadow: var(--shadow-sm);
    transition: all var(--transition-normal);
}

.header.scrolled {
    box-shadow: var(--shadow-md);
}

.header-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: var(--header-height);
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--space-2);
}

.logo img {
    height: 48px;
    width: auto;
}

.logo-text {
    font-family: var(--font-heading);
    font-size: var(--text-xl);
    font-weight: 700;
    color: var(--primary);
}

.nav {
    display: none;
}

.nav-list {
    display: flex;
    align-items: center;
    gap: var(--space-8);
}

.nav-link {
    font-weight: 500;
    color: var(--text-secondary);
    transition: color var(--transition-fast);
    position: relative;
}

.nav-link:hover,
.nav-link.active {
    color: var(--primary);
}

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: -var(--space-2);
    left: 0;
    right: 0;
    height: 2px;
    background: var(--primary);
    border-radius: var(--radius-full);
}

.header-actions {
    display: flex;
    align-items: center;
    gap: var(--space-3);
}

.mobile-toggle {
    display: flex;
    flex-direction: column;
    justify-content: center;
    width: 28px;
    height: 20px;
    cursor: pointer;
}

.mobile-toggle span {
    display: block;
    height: 2px;
    background: var(--text-primary);
    border-radius: var(--radius-full);
    transition: all var(--transition-fast);
}

.mobile-toggle span:not(:last-child) {
    margin-bottom: 6px;
}

/* Mobile Menu */
.mobile-menu {
    position: fixed;
    top: 0;
    right: -100%;
    width: 100%;
    max-width: 320px;
    height: 100vh;
    background: var(--white);
    box-shadow: var(--shadow-2xl);
    z-index: var(--z-modal);
    transition: right var(--transition-slow);
    overflow-y: auto;
}

.mobile-menu.active {
    right: 0;
}

.mobile-menu-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--space-4) var(--space-5);
    border-bottom: 1px solid var(--gray-100);
}

.mobile-menu-close {
    font-size: var(--text-2xl);
    color: var(--text-primary);
}

.mobile-menu-nav {
    padding: var(--space-4);
}

.mobile-nav-link {
    display: block;
    padding: var(--space-4);
    font-size: var(--text-lg);
    font-weight: 500;
    color: var(--text-primary);
    border-radius: var(--radius-lg);
    transition: background var(--transition-fast);
}

.mobile-nav-link:hover {
    background: var(--gray-50);
    color: var(--primary);
}

.menu-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    z-index: calc(var(--z-modal) - 1);
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-normal);
}

.menu-overlay.active {
    opacity: 1;
    visibility: visible;
}

/* ============================================================================
   9. ALERTS & MESSAGES
   ============================================================================ */

.alert {
    display: flex;
    align-items: flex-start;
    gap: var(--space-3);
    padding: var(--space-4);
    border-radius: var(--radius-lg);
    margin-bottom: var(--space-4);
}

.alert-icon {
    font-size: var(--text-xl);
    flex-shrink: 0;
}

.alert-content {
    flex: 1;
}

.alert-title {
    font-weight: 600;
    margin-bottom: var(--space-1);
}

.alert-success {
    background: var(--success-bg);
    color: #065f46;
}

.alert-success .alert-icon {
    color: var(--success);
}

.alert-error {
    background: var(--error-bg);
    color: #991b1b;
}

.alert-error .alert-icon {
    color: var(--error);
}

.alert-warning {
    background: var(--warning-bg);
    color: #92400e;
}

.alert-warning .alert-icon {
    color: var(--warning);
}

.alert-info {
    background: var(--info-bg);
    color: #1e40af;
}

.alert-info .alert-icon {
    color: var(--info);
}

/* Toast Notifications */
.toast-container {
    position: fixed;
    top: var(--space-6);
    right: var(--space-6);
    z-index: var(--z-tooltip);
    display: flex;
    flex-direction: column;
    gap: var(--space-3);
}

.toast {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    padding: var(--space-4) var(--space-5);
    background: var(--white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    min-width: 320px;
    max-width: 420px;
    animation: slideIn 0.3s ease;
}

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

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

/* ============================================================================
   10. ANIMATIONS
   ============================================================================ */

@keyframes fadeIn {
    from {
        opacity: 0;
    }

    to {
        opacity: 1;
    }
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }

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

@keyframes fadeInDown {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }

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

@keyframes scaleIn {
    from {
        opacity: 0;
        transform: scale(0.95);
    }

    to {
        opacity: 1;
        transform: scale(1);
    }
}

@keyframes pulse {

    0%,
    100% {
        opacity: 1;
    }

    50% {
        opacity: 0.5;
    }
}

@keyframes spin {
    from {
        transform: rotate(0deg);
    }

    to {
        transform: rotate(360deg);
    }
}

.animate-fadeIn {
    animation: fadeIn 0.5s ease;
}

.animate-fadeInUp {
    animation: fadeInUp 0.5s ease;
}

.animate-fadeInDown {
    animation: fadeInDown 0.5s ease;
}

.animate-scaleIn {
    animation: scaleIn 0.3s ease;
}

.animate-pulse {
    animation: pulse 2s infinite;
}

.animate-spin {
    animation: spin 1s linear infinite;
}

/* Loading Spinner */
.spinner {
    width: 40px;
    height: 40px;
    border: 3px solid var(--gray-200);
    border-top-color: var(--primary);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

.spinner-sm {
    width: 20px;
    height: 20px;
    border-width: 2px;
}

/* Skeleton Loading */
.skeleton {
    background: linear-gradient(90deg, var(--gray-200) 25%, var(--gray-100) 50%, var(--gray-200) 75%);
    background-size: 200% 100%;
    animation: skeleton 1.5s infinite;
    border-radius: var(--radius-md);
}

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

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

/* ============================================================================
   RESPONSIVE BREAKPOINTS
   ============================================================================ */

/* Tablet (768px+) */
@media (min-width: 768px) {
    .container {
        padding: 0 var(--space-6);
    }

    h1 {
        font-size: var(--text-5xl);
    }

    h2 {
        font-size: var(--text-4xl);
    }

    .nav {
        display: block;
    }

    .mobile-toggle {
        display: none;
    }

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

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

/* Desktop (1024px+) */
@media (min-width: 1024px) {
    .container {
        padding: 0 var(--space-8);
    }

    h1 {
        font-size: var(--text-6xl);
    }

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

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

/* Large Desktop (1280px+) */
@media (min-width: 1280px) {
    .grid-cols-xl-4 {
        grid-template-columns: repeat(4, 1fr);
    }
}