/* 
 * style.css - Main Stylesheet
 * Frontend Developer: Nguyễn Đức Thắng
 * Sprint 1 - KhoaHocIT.Shop
 */

/* ===== CSS VARIABLES ===== */
:root {
    --primary-color: #2563eb;
    --secondary-color: #8b5cf6;
    --success-color: #10b981;
    --danger-color: #ef4444;
    --warning-color: #f59e0b;
    --dark-color: #1f2937;
    --light-color: #f9fafb;
    --text-color: #374151;
    --text-light: #6b7280;
    --border-color: #e5e7eb;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --transition: all 0.3s ease;
}

/* ===== RESET & BASE ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    color: var(--text-color);
    line-height: 1.6;
    background-color: #ffffff;
}

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

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

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

ul {
    list-style: none;
}

/* ===== CONTAINER ===== */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.5rem;
}

/* ===== HEADER & NAVIGATION ===== */
.header {
    background: #ffffff;
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 1000;
}

.navbar {
    padding: 1rem 0;
}

.nav-wrapper {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 2rem;
}

.logo a {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

.logo img {
    height: 40px;
}

.nav-menu {
    display: flex;
    gap: 2rem;
    margin: 0;
}

.nav-menu a {
    padding: 0.5rem 1rem;
    border-radius: var(--radius-md);
    font-weight: 500;
    transition: var(--transition);
}

.nav-menu a:hover,
.nav-menu a.active {
    color: var(--primary-color);
    background-color: rgba(37, 99, 235, 0.1);
}

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

.search-box {
    display: flex;
    align-items: center;
    background: var(--light-color);
    border-radius: var(--radius-md);
    padding: 0.5rem 1rem;
}

.search-box input {
    border: none;
    background: none;
    outline: none;
    width: 200px;
    font-size: 0.875rem;
}

.search-box button {
    color: var(--text-light);
}

.cart-icon {
    position: relative;
    padding: 0.5rem;
    font-size: 1.25rem;
    color: var(--text-color);
}

.cart-icon .badge {
    position: absolute;
    top: 0;
    right: 0;
    background: var(--danger-color);
    color: white;
    font-size: 0.75rem;
    padding: 0.125rem 0.375rem;
    border-radius: 1rem;
}

.mobile-menu-toggle {
    display: none;
    font-size: 1.5rem;
    color: var(--text-color);
}

/* ===== BUTTONS ===== */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.625rem 1.25rem;
    font-size: 0.875rem;
    font-weight: 500;
    border-radius: var(--radius-md);
    transition: var(--transition);
    cursor: pointer;
    text-align: center;
    border: 1px solid transparent;
}

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

.btn-primary:hover {
    background: #1d4ed8;
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.btn-outline {
    border: 2px solid white;
    color: white;
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px);
}

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

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

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

.btn-lg {
    padding: 0.875rem 2rem;
    font-size: 1rem;
}

.btn-sm {
    padding: 0.375rem 0.75rem;
    font-size: 0.8125rem;
}

.btn-block {
    width: 100%;
    justify-content: center;
}

.btn-login {
    background: var(--primary-color);
    color: white;
    padding: 0.625rem 1.5rem;
    border-radius: var(--radius-md);
    font-weight: 500;
    transition: var(--transition);
}

.btn-login:hover {
    background: #1d4ed8;
}

/* ===== HERO BANNER ===== */
.hero-banner {
    background: linear-gradient(135deg, #4f46e5 0%, #7c3aed 100%);
    color: white;
    padding: 4rem 0;
    position: relative;
}

.hero-banner::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.1);
    pointer-events: none;
}

.hero-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
    align-items: center;
}

.hero-title {
    font-size: 3rem;
    font-weight: 800;
    line-height: 1.2;
    margin-bottom: 1rem;
}

.hero-title .highlight {
    color: #fbbf24;
}

.hero-description {
    font-size: 1.125rem;
    margin-bottom: 2rem;
    opacity: 0.9;
}

.hero-buttons {
    display: flex;
    gap: 1rem;
    margin-bottom: 2rem;
}

.hero-stats {
    display: flex;
    gap: 2rem;
}

.stat-item {
    display: flex;
    flex-direction: column;
}

.stat-item strong {
    font-size: 1.5rem;
    font-weight: 700;
}

.stat-item span {
    font-size: 0.875rem;
    opacity: 0.8;
}

.hero-image img {
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
}

/* ===== SECTIONS ===== */
section {
    padding: 4rem 0;
}

.section-header {
    text-align: center;
    margin-bottom: 3rem;
}

.section-title {
    font-size: 2rem;
    font-weight: 700;
    color: var(--dark-color);
    margin-bottom: 0.5rem;
}

.section-subtitle {
    font-size: 1.125rem;
    color: var(--text-light);
}

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

/* ===== CATEGORIES ===== */
.categories-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    gap: 1.5rem;
}

.category-card {
    background: white;
    padding: 2rem 1.5rem;
    border-radius: var(--radius-lg);
    text-align: center;
    cursor: pointer;
    transition: var(--transition);
    border: 2px solid var(--border-color);
}

.category-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
}

.category-icon {
    font-size: 2.5rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.category-name {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--dark-color);
}

.category-count {
    color: var(--text-light);
    font-size: 0.875rem;
}

/* ===== COURSES GRID ===== */
.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 2rem;
}

.course-card {
    background: white;
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    border: 1px solid var(--border-color);
}

.course-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.course-thumbnail {
    position: relative;
    height: 180px;
    overflow: hidden;
}

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

.course-badge {
    position: absolute;
    top: 0.75rem;
    right: 0.75rem;
    background: var(--primary-color);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
    font-weight: 600;
}

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

.course-content {
    padding: 1.5rem;
}

.course-title {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--dark-color);
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.course-instructor {
    color: var(--text-light);
    font-size: 0.875rem;
    margin-bottom: 1rem;
}

.course-meta {
    margin-bottom: 1rem;
}

.course-rating {
    display: flex;
    align-items: center;
    gap: 0.25rem;
    color: var(--warning-color);
    font-size: 0.875rem;
}

.course-rating span {
    color: var(--dark-color);
    font-weight: 600;
}

.course-rating small {
    color: var(--text-light);
}

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

.course-price {
    display: flex;
    flex-direction: column;
}

.price-current {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--danger-color);
}

.price-old {
    font-size: 0.875rem;
    color: var(--text-light);
    text-decoration: line-through;
}

/* ===== CTA SECTION ===== */
.cta-section {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    text-align: center;
}

.cta-title {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 1rem;
}

.cta-description {
    font-size: 1.125rem;
    margin-bottom: 2rem;
    opacity: 0.9;
}

/* ===== FOOTER ===== */
.footer {
    background: var(--dark-color);
    color: white;
    padding: 3rem 0 1rem;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-bottom: 2rem;
}

.footer-col h3 {
    font-size: 1.125rem;
    margin-bottom: 1rem;
}

.footer-col p {
    color: rgba(255, 255, 255, 0.8);
    margin-bottom: 1rem;
}

.footer-col ul li {
    margin-bottom: 0.5rem;
}

.footer-col ul li a {
    color: rgba(255, 255, 255, 0.8);
}

.footer-col ul li a:hover {
    color: var(--primary-color);
}

.social-links {
    display: flex;
    gap: 1rem;
}

.social-links a {
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 50%;
    transition: var(--transition);
}

.social-links a:hover {
    background: var(--primary-color);
    transform: translateY(-3px);
}

.contact-info li {
    margin-bottom: 0.75rem;
    color: rgba(255, 255, 255, 0.8);
}

.contact-info i {
    margin-right: 0.5rem;
    color: var(--primary-color);
}

.footer-bottom {
    text-align: center;
    padding-top: 2rem;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    color: rgba(255, 255, 255, 0.6);
}

.footer-bottom p {
    margin: 0.25rem 0;
}

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

.mt-4 {
    margin-top: 2rem;
}

.mb-4 {
    margin-bottom: 2rem;
}