:root {
    --primary-color: #3b608e;
    --secondary-color: #648cbe;
    --accent-color: #ff6552;
    --text-dark: #1f2937;
    --text-light: #4b5563;
    --background-light: #f3f7fb;
    --background-white: #ffffff;
    --font-primary: 'Inter', sans-serif;
    --font-heading: 'Pattaya', sans-serif;
    --font-special: 'Pacifico', cursive;
    --border-radius: 8px;
    --box-shadow: 0 5px 15px rgba(0, 0, 0, 0.08);
    --transition: all 0.3s ease-in-out;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-primary);
    font-size: 16px;
    line-height: 1.6;
    color: var(--text-light);
    background-color: var(--background-white);
}

.nutclick{
    margin: 0 auto;
    text-align: center;
    background-color: rgb(140, 184, 140);
    color: black;
   
    border-radius: 20px;
    height: 40px;
    width: 180px;
}
.nutclick:hover{
    background-color: red;
    color: white;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 15px;
}

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

ul {
    list-style: none;
}

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

/* 2. UTILITY CLASSES */
.section-subtitle {
    color: var(--primary-color);
    font-weight: 700;
    text-transform: uppercase;
    font-size: 16px;
    margin-bottom: 8px;
}

.section-title {
    color: var(--text-dark);
    font-size: 36px;
    font-weight: 800;
    margin-bottom: 24px;
    line-height: 1.3;
}

/* 3. HEADER STYLES */
/* - Top Header */
.top-header {
    background-color: #f3f7fb;
    padding: 10px 0;
    font-size: 14px;
    font-weight: 700;
    color: var(--primary-color);
}

.top-header .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.contact-info a {
    margin: 0 10px;
}

.contact-info a:hover {
    color: var(--text-dark);
}

.contact-info i {
    margin-right: 5px;
}

.contact-info .separator {
    display: inline-block;
    width: 1px;
    height: 16px;
    background-color: #ecf1f9;
    vertical-align: middle;
}

.language-switcher a {
    margin-left: 10px;
}

.language-switcher img {
    width: 20px;
    height: auto;
}

/* - Main Navigation */
.main-nav {
    background-color: var(--background-white);
    padding: 15px 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: var(--box-shadow);
    transition: var(--transition);
}

.main-nav.scrolled {
    padding: 10px 0;
}

.main-nav .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo img {
    max-height: 50px;
    transition: var(--transition);
}

.main-nav.scrolled .logo img {
     max-height: 45px;
}

.nav-menu {
    display: flex;
    gap: 30px;
}

.nav-link {
    font-size: 16px;
    font-weight: 800;
    color: var(--primary-color);
    text-transform: uppercase;
    padding: 5px 0;
    border-bottom: 4px solid transparent;
}

.nav-link:hover, .nav-link.active {
    color: var(--secondary-color);
    border-bottom-color: var(--accent-color);
}

.mobile-menu-toggle {
    display: none;
    background: none;
    border: none;
    font-size: 24px;
    color: var(--primary-color);
    cursor: pointer;
}

/* 4. HERO SECTION */
.hero-section {
    position: relative;
    height: 85vh;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    color: var(--background-white);
    overflow: hidden;
}

.hero-background {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image: url('https://tanhuy1.id.vn/img/tanhuy1.jpg.png');
    background-size: cover;
    background-position: center;
    z-index: -1;
}

.hero-background::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(15, 34, 57, 0.7);
}

.hero-content h1 {
    font-family: var(--font-heading);
    font-size: 64px;
    margin-bottom: 10px;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.5);
}

.hero-content h2 {
    font-size: 28px;
    font-weight: 500;
    margin-bottom: 20px;
     text-shadow: 1px 1px 3px rgba(0,0,0,0.5);
}

.hero-content p {
    font-size: 18px;
    max-width: 600px;
    margin: 0 auto 30px;
}

/* 5. ABOUT SECTION */
.about-section {
    padding: 80px 0;
    background: var(--background-light);
}

.about-section .container {
    display: flex;
    align-items: center;
    gap: 50px;
}

.about-image-column {
    flex: 0 0 45%;
}

.about-image-column img {
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
}

.about-content-column {
    flex: 1;
}

.about-text {
    margin-bottom: 20px;
}

.about-features {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 15px;
    margin-top: 30px;
}

.feature-item {
    display: flex;
    align-items: center;
    gap: 10px;
    font-weight: 500;
    color: var(--text-dark);
}

.feature-item i {
    color: var(--primary-color);
}

/* 6. COURSES SECTION */
.courses-section {
    padding: 80px 0;
    background-image: url('https://vutuananhdev.id.vn/datafiles/web30s/upload/images/1101-1200/30S-03-1194/course_bg_1.png');
    background-size: cover;
    background-position: center;
}

.courses-section .section-title, .courses-section .section-subtitle {
    text-align: center;
}

/* 7. BLOG SECTION */
.blog-section {
    padding: 80px 0;
    background-color: var(--background-light);
}

.blog-section .section-title, .blog-section .section-subtitle {
    text-align: center;
}

.blog-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 30px;
    margin-top: 40px;
}

/* 8. FOOTER STYLES */
/* - Main Footer */
.footer {
    background-image: url('https://vutuananhdev.id.vn/datafiles/web30s/upload/images/1101-1200/30S-03-1194/footer-bg.png');
    background-size: cover;
    background-position: center;
    color: var(--background-light);
}

.footer-main {
    padding: 60px 0 40px;
}

.footer-main .container {
    display: grid;
    grid-template-columns: 2fr 1fr 1.5fr;
    gap: 50px;
}

.footer-logo {
    width: 100px;
    margin-bottom: 20px;
}

.footer-title {
    font-size: 20px;
    font-weight: 600;
    color: var(--background-white);
    margin-bottom: 20px;
    text-transform: capitalize;
}

.about-us p {
    font-size: 15px;
    color: #b3c1d3;
    margin-bottom: 20px;
}

.social-media {
    display: flex;
    gap: 10px;
}

.social-media a {
    width: 45px;
    height: 45px;
    border-radius: 50%;
    background-color: #1e2c46;
    color: #b3c1d3;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 16px;
}

.social-media a:hover {
    background-color: var(--primary-color);
    color: var(--background-white);
}

.quick-links ul li a {
    color: #b3c1d3;
    padding: 5px 0;
    display: block;
}

.quick-links ul li a:hover {
    color: var(--primary-color);
}

.newsletter-form {
    display: flex;
    margin-top: 10px;
}

.newsletter-form input {
    flex-grow: 1;
    border: 1px solid var(--primary-color);
    background: transparent;
    padding: 12px 15px;
    color: var(--background-white);
    border-radius: var(--border-radius) 0 0 var(--border-radius);
    outline: none;
}

.newsletter-form input::placeholder {
    color: #b3c1d3;
}

.newsletter-form button {
    border: none;
    background-color: var(--primary-color);
    color: var(--background-white);
    padding: 12px 20px;
    cursor: pointer;
    border-radius: 0 var(--border-radius) var(--border-radius) 0;
    transition: var(--transition);
}

.newsletter-form button:hover {
    background-color: var(--secondary-color);
}

/* - Bottom Footer */
.footer-bottom {
    padding: 20px 0;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

.footer-bottom .container {
    display: flex;
    justify-content: center;
    align-items: center;
    flex-wrap: wrap;
    gap: 10px;
    text-align: center;
    font-size: 15px;
    color: #b3c1d3;
}

.footer-bottom a {
    color: #b3c1d3;
    font-weight: 500;
}
.footer-bottom a:hover {
    color: var(--primary-color);
}

/* 9. COMPONENTS */
/* - Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 12px 28px;
    border-radius: var(--border-radius);
    font-weight: 700;
    text-transform: uppercase;
    font-size: 14px;
    border: none;
    cursor: pointer;
    transition: var(--transition);
}

.btn-primary {
    background-color: var(--primary-color);
    color: var(--background-white);
    box-shadow: 0 4px 10px rgba(59, 96, 142, 0.3);
}

.btn-primary:hover {
    background-color: var(--secondary-color);
    transform: translateY(-2px);
}

.btn-nav {
    padding: 15px 30px;
}

.btn-secondary {
    background-color: var(--accent-color);
    color: var(--background-white);
}
.btn-secondary:hover {
    background-color: #e55a4a;
}

/* - Course Card */
.course-card {
    background: var(--background-white);
    border-radius: var(--border-radius);
    overflow: hidden;
    box-shadow: var(--box-shadow);
    transition: var(--transition);
    height: 100%;
    display: flex;
    flex-direction: column;
}

.course-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 20px rgba(0,0,0,0.1);
}

.course-image {
    width: 100%;
    aspect-ratio: 16 / 10;
    object-fit: cover;
}

.course-info {
    padding: 20px;
    flex-grow: 1;
    display: flex;
    flex-direction: column;
}

.course-title {
    font-size: 18px;
    color: var(--text-dark);
    font-weight: 700;
    margin-bottom: 10px;
    height: 54px; /* for 2 lines */
    overflow: hidden;
}

.course-desc {
    font-size: 14px;
    flex-grow: 1;
    margin-bottom: 15px;
}

.course-price {
    font-size: 20px;
    font-weight: 800;
    color: var(--accent-color);
    margin-bottom: 15px;
}


/* - Blog Card */
.blog-card {
    background: var(--background-white);
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    overflow: hidden;
    transition: var(--transition);
}

.blog-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 20px rgba(0,0,0,0.1);
}

.blog-image {
     width: 100%;
    aspect-ratio: 16 / 10;
    object-fit: cover;
}
.blog-content {
    padding: 25px;
}

.blog-meta {
    font-size: 14px;
    color: var(--text-light);
    margin-bottom: 15px;
}

.blog-meta span {
    margin-right: 15px;
}

.blog-title {
    font-size: 20px;
    font-weight: 700;
    color: var(--text-dark);
    margin-bottom: 15px;
    line-height: 1.4;
    height: 56px; /* for 2 lines */
    overflow: hidden;
}

.blog-readmore {
    font-weight: 700;
    color: var(--primary-color);
}

.blog-readmore:hover {
    color: var(--accent-color);
}

/* - Swiper Slider */
.swiper-pagination-bullet {
    background: var(--primary-color);
    opacity: 0.5;
}
.swiper-pagination-bullet-active {
    opacity: 1;
}

/* 10. SCROLL TO TOP BUTTON */
.scroll-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    background-color: var(--background-white);
    color: var(--primary-color);
    border: 3px solid var(--primary-color);
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 20px;
    z-index: 999;
    opacity: 0;
    visibility: hidden;
    transition: var(--transition);
}

.scroll-to-top.visible {
    opacity: 1;
    visibility: visible;
}

.scroll-to-top:hover {
    background-color: var(--primary-color);
    color: var(--background-white);
}

/* 11. RESPONSIVE DESIGN */
@media (max-width: 1024px) {
    .nav-menu {
        display: none;
        flex-direction: column;
        position: fixed;
        top: 0;
        right: -300px;
        width: 300px;
        height: 100vh;
        background-color: var(--background-white);
        padding-top: 80px;
        box-shadow: -5px 0 15px rgba(0,0,0,0.1);
        transition: right 0.4s ease;
        gap: 0;
    }
    
    .nav-menu.active {
        right: 0;
    }

    .nav-item {
        width: 100%;
    }
    
    .nav-link {
        display: block;
        padding: 15px 25px;
        border-bottom: 1px solid #eee;
    }
     .nav-link:hover, .nav-link.active {
        border-bottom-color: #eee;
        background-color: #f9f9f9;
    }
    
    .mobile-menu-toggle {
        display: block;
    }
    
    .btn-nav {
        display: none;
    }

    .about-section .container {
        flex-direction: column;
    }

    .footer-main .container {
        grid-template-columns: 1fr 1fr;
    }
    .about-us {
        grid-column: 1 / -1;
    }
}

@media (max-width: 768px) {
    .section-title {
        font-size: 28px;
    }
    
    .hero-content h1 {
        font-size: 48px;
    }
    
    .hero-content h2 {
        font-size: 22px;
    }

    .about-features {
        grid-template-columns: 1fr;
    }
    
    .footer-main .container {
        grid-template-columns: 1fr;
        text-align: center;
    }

    .footer-logo, .social-media, .newsletter-form {
        margin-left: auto;
        margin-right: auto;
        justify-content: center;
    }

    .footer-bottom .container {
        flex-direction: column;
    }

}