/* ========================================
   VDolsAI - Premium AI Education Platform
   Main Stylesheet
   ======================================== */

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

/* ====== ROOT & COLORS ====== */
:root {
    --color-bg: #0a0e27;
    --color-bg-darker: #050810;
    --color-text: #e8eef5;
    --color-text-muted: #a8b2cc;
    --color-primary: #6366f1;
    --color-primary-glow: #818cf8;
    --color-accent-cyan: #06b6d4;
    --color-accent-pink: #ec4899;
    --color-accent-purple: #a855f7;
    --color-card-bg: rgba(30, 41, 82, 0.3);
    --color-card-border: rgba(99, 102, 241, 0.1);
    --color-hover-bg: rgba(99, 102, 241, 0.05);
    --color-success: #10b981;
    --color-warning: #f59e0b;
    
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 16px 48px rgba(0, 0, 0, 0.5);
    
    --transition-fast: 0.2s ease-in-out;
    --transition-medium: 0.4s ease-in-out;
    --transition-slow: 0.6s ease-in-out;
}

/* ====== TYPOGRAPHY ====== */
html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', 'Segoe UI', sans-serif;
    background: linear-gradient(135deg, var(--color-bg) 0%, var(--color-bg-darker) 100%);
    color: var(--color-text);
    line-height: 1.6;
    overflow-x: hidden;
    min-height: 100vh;
}

h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.3;
    letter-spacing: -0.02em;
}

h1 {
    font-size: 4rem;
    margin-bottom: 1.5rem;
}

h2 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

h3 {
    font-size: 1.75rem;
    margin-bottom: 0.75rem;
}

h4 {
    font-size: 1.25rem;
    margin-bottom: 0.5rem;
}

p {
    font-size: 1rem;
    color: var(--color-text-muted);
    margin-bottom: 1rem;
    line-height: 1.7;
}

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

a:hover {
    color: var(--color-accent-cyan);
    text-decoration: underline;
}

/* ====== BUTTONS ====== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.875rem 1.75rem;
    font-size: 1rem;
    font-weight: 600;
    text-decoration: none;
    border: none;
    border-radius: 0.75rem;
    cursor: pointer;
    transition: all var(--transition-fast);
    position: relative;
    overflow: hidden;
}

.btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: radial-gradient(circle, rgba(255, 255, 255, 0.1) 0%, transparent 70%);
    opacity: 0;
    transition: opacity var(--transition-fast);
}

.btn:hover::before {
    opacity: 1;
}

.btn-primary {
    background: linear-gradient(135deg, var(--color-primary) 0%, #7c3aed 100%);
    color: white;
    box-shadow: 0 0 20px rgba(99, 102, 241, 0.4),
                0 8px 16px rgba(0, 0, 0, 0.3);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 0 30px rgba(99, 102, 241, 0.6),
                0 12px 24px rgba(0, 0, 0, 0.4);
}

.btn-secondary {
    background: transparent;
    color: var(--color-accent-cyan);
    border: 1.5px solid var(--color-accent-cyan);
    box-shadow: 0 0 15px rgba(6, 182, 212, 0.2);
}

.btn-secondary:hover {
    background: rgba(6, 182, 212, 0.1);
    box-shadow: 0 0 25px rgba(6, 182, 212, 0.4);
    transform: translateY(-2px);
}

.btn-large {
    padding: 1.25rem 2.5rem;
    font-size: 1.125rem;
}

.btn-small {
    padding: 0.625rem 1.25rem;
    font-size: 0.875rem;
}

/* ====== CONTAINER & SPACING ====== */
.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 2rem;
}

.section {
    padding: 6rem 0;
    position: relative;
    overflow: hidden;
}

.section-title {
    text-align: center;
    margin-bottom: 4rem;
}

.section-title h2 {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.section-title p {
    font-size: 1.125rem;
    color: var(--color-text-muted);
    max-width: 600px;
    margin: 0 auto;
}

/* ====== HEADER ====== */
header {
    position: sticky;
    top: 0;
    z-index: 1000;
    background: rgba(10, 14, 39, 0.7);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid rgba(99, 102, 241, 0.1);
    padding: 1rem 0;
    transition: all var(--transition-fast);
}

header.scrolled {
    background: rgba(5, 8, 16, 0.9);
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
}

.header-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 80px;
}

.logo {
    font-size: 1.5rem;
    font-weight: 800;
    color: white;
    text-decoration: none;
    letter-spacing: -0.03em;
    transition: all var(--transition-fast);
}

.logo:hover {
    color: var(--color-accent-cyan);
    text-shadow: 0 0 20px rgba(6, 182, 212, 0.5);
}

.logo span {
    color: var(--color-primary-glow);
}

nav ul {
    display: flex;
    list-style: none;
    gap: 2rem;
    align-items: center;
}

nav a {
    color: var(--color-text-muted);
    font-weight: 500;
    transition: all var(--transition-fast);
    position: relative;
}

nav a::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 0;
    height: 2px;
    background: linear-gradient(90deg, var(--color-primary) 0%, var(--color-accent-cyan) 100%);
    transition: width var(--transition-fast);
}

nav a:hover {
    color: var(--color-text);
}

nav a:hover::after {
    width: 100%;
}

.header-right {
    display: flex;
    align-items: center;
    gap: 1.5rem;
}

.mobile-menu-btn {
    display: none;
    background: none;
    border: none;
    color: white;
    font-size: 1.5rem;
    cursor: pointer;
}

/* ====== FOOTER ====== */
footer {
    background: rgba(5, 8, 16, 0.8);
    border-top: 1px solid rgba(99, 102, 241, 0.1);
    padding: 4rem 0 2rem;
    margin-top: 6rem;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 3rem;
    margin-bottom: 3rem;
}

.footer-section h4 {
    color: white;
    margin-bottom: 1.5rem;
    font-size: 1rem;
}

.footer-section ul {
    list-style: none;
}

.footer-section ul li {
    margin-bottom: 0.75rem;
}

.footer-section a {
    color: var(--color-text-muted);
    font-size: 0.9rem;
}

.footer-section a:hover {
    color: var(--color-accent-cyan);
}

.footer-bottom {
    border-top: 1px solid rgba(99, 102, 241, 0.1);
    padding-top: 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    color: var(--color-text-muted);
    font-size: 0.875rem;
}

/* ====== HERO SECTION ====== */
.hero {
    min-height: calc(100vh - 80px);
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    overflow: hidden;
    padding: 4rem 0;
}

.hero::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -10%;
    width: 600px;
    height: 600px;
    background: radial-gradient(circle, rgba(99, 102, 241, 0.15) 0%, transparent 70%);
    border-radius: 50%;
    animation: float 20s ease-in-out infinite;
}

.hero::after {
    content: '';
    position: absolute;
    bottom: -20%;
    left: -5%;
    width: 500px;
    height: 500px;
    background: radial-gradient(circle, rgba(6, 182, 212, 0.1) 0%, transparent 70%);
    border-radius: 50%;
    animation: float 25s ease-in-out infinite reverse;
}

.hero-content {
    position: relative;
    z-index: 2;
    max-width: 1200px;
    width: 100%;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4rem;
    align-items: center;
}

.hero-text h1 {
    font-size: 3.5rem;
    line-height: 1.2;
    margin-bottom: 1.5rem;
    background: linear-gradient(135deg, white 0%, var(--color-primary-glow) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-text p {
    font-size: 1.25rem;
    color: var(--color-text-muted);
    margin-bottom: 2rem;
    line-height: 1.8;
}

.hero-buttons {
    display: flex;
    gap: 1.5rem;
}

.hero-visual {
    position: relative;
    height: 500px;
}

.hero-visual-item {
    position: absolute;
    border-radius: 1rem;
    overflow: hidden;
    box-shadow: 0 10px 40px rgba(0, 0, 0, 0.4);
    border: 1px solid rgba(99, 102, 241, 0.2);
}

.hero-visual-item img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.hero-visual-item:nth-child(1) {
    width: 280px;
    height: 300px;
    top: 0;
    left: 0;
    animation: float-item 6s ease-in-out infinite;
}

.hero-visual-item:nth-child(2) {
    width: 250px;
    height: 280px;
    top: 100px;
    right: 0;
    animation: float-item 7s ease-in-out infinite reverse;
}

.hero-visual-item:nth-child(3) {
    width: 220px;
    height: 250px;
    bottom: 0;
    left: 100px;
    animation: float-item 8s ease-in-out infinite;
}

/* ====== CARDS ====== */
.card {
    background: var(--color-card-bg);
    border: 1px solid var(--color-card-border);
    border-radius: 1rem;
    padding: 2rem;
    transition: all var(--transition-medium);
    backdrop-filter: blur(10px);
    position: relative;
    overflow: hidden;
}

.card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.1) 0%, transparent 50%);
    opacity: 0;
    transition: opacity var(--transition-medium);
}

.card:hover {
    border-color: rgba(99, 102, 241, 0.3);
    box-shadow: 0 0 30px rgba(99, 102, 241, 0.2),
                0 10px 30px rgba(0, 0, 0, 0.3);
    transform: translateY(-8px);
}

.card:hover::before {
    opacity: 1;
}

.card-content {
    position: relative;
    z-index: 1;
}

.card-icon {
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-accent-purple) 100%);
    border-radius: 0.75rem;
    font-size: 1.5rem;
    margin-bottom: 1rem;
}

.card-title {
    font-size: 1.25rem;
    color: white;
    margin-bottom: 0.75rem;
    font-weight: 700;
}

.card-description {
    color: var(--color-text-muted);
    font-size: 0.95rem;
    line-height: 1.6;
}

/* ====== GRID LAYOUTS ====== */
.grid-2 {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 2rem;
}

.grid-3 {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 2rem;
}

.grid-4 {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 2rem;
}

/* ====== STATS SECTION ====== */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 2rem;
    margin: 4rem 0;
}

.stat-box {
    background: var(--color-card-bg);
    border: 1px solid var(--color-card-border);
    border-radius: 1rem;
    padding: 2rem;
    text-align: center;
    backdrop-filter: blur(10px);
    transition: all var(--transition-medium);
}

.stat-box:hover {
    border-color: rgba(99, 102, 241, 0.3);
    box-shadow: 0 0 20px rgba(99, 102, 241, 0.2);
}

.stat-number {
    font-size: 2.5rem;
    font-weight: 800;
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-accent-cyan) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 0.5rem;
}

.stat-label {
    color: var(--color-text-muted);
    font-size: 0.95rem;
}

/* ====== COURSE CARDS ====== */
.course-card {
    background: var(--color-card-bg);
    border: 1px solid var(--color-card-border);
    border-radius: 1.25rem;
    overflow: hidden;
    transition: all var(--transition-medium);
    backdrop-filter: blur(10px);
    display: flex;
    flex-direction: column;
    height: 100%;
}

.course-image {
    width: 100%;
    height: 240px;
    object-fit: cover;
    transition: transform var(--transition-medium);
}

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

.course-body {
    padding: 2rem;
    flex-grow: 1;
    display: flex;
    flex-direction: column;
}

.course-badge {
    display: inline-block;
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-accent-purple) 100%);
    color: white;
    padding: 0.5rem 1rem;
    border-radius: 0.5rem;
    font-size: 0.75rem;
    font-weight: 600;
    margin-bottom: 1rem;
    width: fit-content;
}

.course-title {
    font-size: 1.25rem;
    color: white;
    margin-bottom: 0.75rem;
    font-weight: 700;
}

.course-description {
    color: var(--color-text-muted);
    font-size: 0.95rem;
    margin-bottom: 1.5rem;
    flex-grow: 1;
}

.course-meta {
    display: flex;
    gap: 1.5rem;
    margin-bottom: 1.5rem;
    font-size: 0.9rem;
    color: var(--color-text-muted);
}

.course-meta-item {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.course-card:hover {
    border-color: rgba(99, 102, 241, 0.3);
    box-shadow: 0 0 30px rgba(99, 102, 241, 0.2),
                0 10px 30px rgba(0, 0, 0, 0.3);
    transform: translateY(-8px);
}

/* ====== REVIEW CARDS ====== */
.review-card {
    background: var(--color-card-bg);
    border: 1px solid var(--color-card-border);
    border-radius: 1rem;
    padding: 2rem;
    backdrop-filter: blur(10px);
    transition: all var(--transition-medium);
}

.review-header {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.review-avatar {
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-accent-purple) 100%);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-weight: 700;
    font-size: 1.25rem;
}

.review-info h4 {
    color: white;
    margin-bottom: 0.25rem;
    font-size: 1rem;
}

.review-info p {
    font-size: 0.85rem;
    color: var(--color-text-muted);
    margin: 0;
}

.review-rating {
    display: flex;
    gap: 0.25rem;
    margin-bottom: 1rem;
    color: var(--color-warning);
}

.review-text {
    color: var(--color-text-muted);
    font-size: 0.95rem;
    line-height: 1.7;
}

.review-card:hover {
    border-color: rgba(99, 102, 241, 0.3);
    transform: translateY(-4px);
    box-shadow: 0 0 20px rgba(99, 102, 241, 0.15);
}

/* ====== ACCORDION ====== */
.accordion-item {
    border: 1px solid rgba(99, 102, 241, 0.1);
    border-radius: 0.75rem;
    margin-bottom: 1rem;
    background: var(--color-card-bg);
    overflow: hidden;
    backdrop-filter: blur(10px);
}

.accordion-header {
    background: transparent;
    border: none;
    color: white;
    width: 100%;
    padding: 1.5rem;
    text-align: left;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 1rem;
    font-weight: 600;
    transition: all var(--transition-fast);
}

.accordion-header:hover {
    background: rgba(99, 102, 241, 0.05);
    color: var(--color-accent-cyan);
}

.accordion-icon {
    transition: transform var(--transition-medium);
    color: var(--color-primary-glow);
}

.accordion-item.active .accordion-icon {
    transform: rotate(180deg);
}

.accordion-content {
    display: none;
    padding: 0 1.5rem 1.5rem;
    color: var(--color-text-muted);
    line-height: 1.7;
    max-height: 0;
    overflow: hidden;
}

.accordion-item.active .accordion-content {
    display: block;
    animation: slideDown var(--transition-medium) ease-out;
}

/* ====== FORMS ====== */
.form-group {
    margin-bottom: 1.5rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    color: white;
    font-weight: 500;
    font-size: 0.95rem;
}

.form-group input,
.form-group textarea {
    width: 100%;
    padding: 0.875rem 1rem;
    background: rgba(30, 41, 82, 0.5);
    border: 1px solid rgba(99, 102, 241, 0.2);
    border-radius: 0.75rem;
    color: white;
    font-family: inherit;
    font-size: 1rem;
    transition: all var(--transition-fast);
    backdrop-filter: blur(10px);
}

.form-group input:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--color-primary);
    background: rgba(30, 41, 82, 0.7);
    box-shadow: 0 0 20px rgba(99, 102, 241, 0.2);
}

.form-group textarea {
    resize: vertical;
    min-height: 150px;
}

.form-group input::placeholder,
.form-group textarea::placeholder {
    color: rgba(168, 178, 204, 0.5);
}

/* ====== FILTERS ====== */
.filter-tabs {
    display: flex;
    gap: 1rem;
    margin-bottom: 3rem;
    flex-wrap: wrap;
    justify-content: center;
}

.filter-btn {
    padding: 0.75rem 1.5rem;
    background: transparent;
    border: 1.5px solid rgba(99, 102, 241, 0.2);
    color: var(--color-text-muted);
    border-radius: 0.75rem;
    cursor: pointer;
    transition: all var(--transition-fast);
    font-weight: 500;
    font-size: 0.95rem;
}

.filter-btn:hover,
.filter-btn.active {
    border-color: var(--color-primary);
    color: white;
    background: rgba(99, 102, 241, 0.1);
    box-shadow: 0 0 20px rgba(99, 102, 241, 0.2);
}

/* ====== ANIMATIONS ====== */
@keyframes float {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-30px); }
}

@keyframes float-item {
    0%, 100% { transform: translateY(0) rotateZ(0deg); }
    50% { transform: translateY(-20px) rotateZ(2deg); }
}

@keyframes slideDown {
    from {
        opacity: 0;
        max-height: 0;
    }
    to {
        opacity: 1;
        max-height: 500px;
    }
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes glow-pulse {
    0%, 100% {
        box-shadow: 0 0 20px rgba(99, 102, 241, 0.4);
    }
    50% {
        box-shadow: 0 0 40px rgba(99, 102, 241, 0.6);
    }
}

.animate-on-scroll {
    opacity: 0;
    transform: translateY(30px);
}

.animate-on-scroll.visible {
    animation: fadeInUp 0.8s ease-out forwards;
}

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

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

.glow-effect {
    box-shadow: 0 0 30px rgba(99, 102, 241, 0.3);
}

.glassmorphism {
    background: rgba(30, 41, 82, 0.3);
    backdrop-filter: blur(10px);
    border: 1px solid rgba(99, 102, 241, 0.1);
}

.mt-1 { margin-top: 0.5rem; }
.mt-2 { margin-top: 1rem; }
.mt-3 { margin-top: 1.5rem; }
.mt-4 { margin-top: 2rem; }
.mt-6 { margin-top: 3rem; }

.mb-1 { margin-bottom: 0.5rem; }
.mb-2 { margin-bottom: 1rem; }
.mb-3 { margin-bottom: 1.5rem; }
.mb-4 { margin-bottom: 2rem; }
.mb-6 { margin-bottom: 3rem; }

.gap-2 { gap: 1rem; }
.gap-3 { gap: 1.5rem; }
.gap-4 { gap: 2rem; }