:root {
    --primary: #004d40; /* Deeper, richer green */
    --secondary: #e53935; /* Vibrant red */
    --accent: #ffb300; /* Golden accent */
    --light: #ffffff; /* Pure white for cleaner contrast */
    --dark: #1a1a1a; /* Slightly darker for sharper text */
    --gray: #f5f6f5; /* Softer gray for modern elegance */
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.12);
    --shadow-lg: 0 8px 28px rgba(0, 0, 0, 0.16);
    --border-radius: 12px; /* Slightly larger for modern feel */
    --transition-ease: all 0.3s cubic-bezier(0.4, 0, 0.2, 1); /* Google-like smooth easing */
}

* {
    box-sizing: border-box;
    -webkit-font-smoothing: antialiased; /* Crisp text rendering */
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: 'Google Sans', 'Inter', 'Roboto', system-ui, sans-serif; /* Google Sans for premium feel */
    margin: 0;
    padding: 0;
    background-color: var(--gray);
    color: var(--dark);
    line-height: 1.6;
    scroll-behavior: smooth;
    font-size: 16px; /* Base font size for accessibility */
}

.container {
    width: 90%;
    max-width: 1400px; /* Wider for larger screens */
    margin: 0 auto;
    padding: 32px 0;
}

/* Header Styles */
header {
    background: var(--light);
    color: var(--dark);
    padding: 16px 0;
    border-bottom: 4px solid var(--primary);
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: var(--shadow-sm);
    transition: var(--transition-ease);
}

header.scrolled {
    padding: 8px 0;
    box-shadow: var(--shadow-md);
}

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

.logo {
    display: flex;
    align-items: center;
    font-weight: 700;
    font-size: 1.8rem;
    color: var(--primary);
    gap: 10px;
    text-transform: uppercase;
    letter-spacing: 0.3px;
    transition: var(--transition-ease);
}

.logo img {
    width: 40px;
    height: 40px;
    border-radius: 8px;
    transition: var(--transition-ease);
}

.logo:hover {
    transform: translateY(-2px);
}

nav ul {
    display: flex;
    gap: 32px;
    margin: 0;
    padding: 0;
    list-style: none;
}

nav a {
    color: var(--dark);
    text-decoration: none;
    font-weight: 600;
    font-size: 1rem;
    transition: var(--transition-ease);
    position: relative;
    padding: 8px 0;
    text-transform: uppercase;
}

nav a:hover,
nav a.active {
    color: var(--secondary);
}

nav a::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 50%;
    transform: translateX(-50%);
    width: 0;
    height: 2px;
    background: var(--secondary);
    border-radius: 2px;
    transition: var(--transition-ease);
}

nav a:hover::after,
nav a.active::after {
    width: 80%;
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, rgba(0, 77, 64, 0.9), rgba(0, 77, 64, 0.7)), 
                url('https://via.placeholder.com/1500x600.png?text=Empowering+Future+Minds+with+Innovation') no-repeat center center/cover;
    color: var(--light);
    text-align: center;
    padding: 160px 24px;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(45deg, rgba(255,255,255,0.08) 25%, transparent 25%, transparent 75%, rgba(255,255,255,0.08) 75%);
    background-size: 40px 40px;
    opacity: 0.12;
    z-index: 1;
}

.hero-content {
    position: relative;
    z-index: 2;
    max-width: 1000px;
    margin: 0 auto;
}

.hero h1 {
    font-size: clamp(2.8rem, 5.5vw, 4.8rem);
    margin-bottom: 24px;
    line-height: 1.2;
    font-weight: 800;
    text-shadow: 0 2px 8px rgba(0, 0, 0, 0.25);
    letter-spacing: -0.5px;
}

.hero p {
    font-size: clamp(1.2rem, 2vw, 1.7rem);
    margin-bottom: 48px;
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
    opacity: 0.95;
    font-weight: 400;
}

/* Button Styles */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    background: var(--secondary);
    color: var(--light);
    padding: 14px 32px;
    text-decoration: none;
    border-radius: 100px; /* Pill-shaped buttons */
    font-weight: 600;
    font-size: 1.1rem;
    transition: var(--transition-ease);
    border: none;
    cursor: pointer;
    gap: 8px;
    position: relative;
    overflow: hidden;
    box-shadow: var(--shadow-sm);
}

.btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(45deg, var(--secondary), #ff6e6e);
    z-index: -1;
    transition: var(--transition-ease);
    transform: scaleX(0);
    transform-origin: left;
}

.btn:hover::before {
    transform: scaleX(1);
}

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

.btn-secondary {
    background: var(--light);
    color: var(--primary);
    border: 1px solid var(--primary);
    margin-left: 16px;
}

.btn-secondary::before {
    background: linear-gradient(45deg, var(--light), #f0f0f0);
}

.btn-secondary:hover {
    box-shadow: var(--shadow-md);
}

/* Section Styles */
.section {
    padding: 80px 0;
    text-align: center;
    background-color: var(--light);
    position: relative;
    z-index: 1;
}

.section:nth-of-type(even) {
    background-color: var(--gray);
}

.section h2 {
    font-size: clamp(2.2rem, 4vw, 3.2rem);
    margin-bottom: 40px;
    color: var(--primary);
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.3px;
    position: relative;
}

.section h2::after {
    content: '';
    position: absolute;
    bottom: -12px;
    left: 50%;
    transform: translateX(-50%);
    width: 80px;
    height: 3px;
    background: var(--secondary);
    border-radius: 2px;
}

/* Grid Layouts */
.gallery-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 24px;
    margin-top: 32px;
}

.gallery-grid img {
    width: 100%;
    height: 240px;
    object-fit: cover;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-md);
    transition: var(--transition-ease);
}

.gallery-grid img:hover {
    transform: scale(1.05);
    box-shadow: var(--shadow-lg);
    border: 2px solid var(--accent);
}

/* Levels Grid */
.levels-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 32px;
    text-align: left;
}

.level-card {
    background: var(--light);
    padding: 24px;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-md);
    border-left: 5px solid var(--primary);
    transition: var(--transition-ease);
}

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

.level-card h3 {
    color: var(--secondary);
    margin-top: 0;
    font-size: 1.6rem;
    font-weight: 600;
}

.level-card p {
    font-size: 1rem;
    color: #333;
}

/* About Section */
.about-content {
    text-align: left;
    line-height: 1.7;
    max-width: 1000px;
    margin: 0 auto;
    font-size: 1.1rem;
}

.about-content .bengali-text {
    font-family: 'Noto Serif Bengali', serif; /* Google-standard font for Bengali */
    font-size: 1.2rem;
    margin-top: 24px;
    color: #333;
}

/* Registration Section */
.registration-info {
    max-width: 1000px;
    margin: 0 auto;
    background: var(--light);
    padding: 48px;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-md);
    text-align: center;
    border: 1px solid rgba(0, 77, 64, 0.1);
}

.registration-info .btn {
    font-size: 1.15rem;
    padding: 16px 40px;
    margin-top: 24px;
}

/* Contact Section */
.contact-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
    gap: 40px;
    text-align: left;
}

.contact-info p {
    font-size: 1.1rem;
    line-height: 1.7;
    color: #333;
}

.contact-info strong {
    color: var(--primary);
}

.contact-form {
    background: var(--light);
    padding: 32px;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-md);
    border-top: 4px solid var(--accent);
}

.contact-form input,
.contact-form textarea {
    width: calc(100% - 20px);
    padding: 14px;
    margin-bottom: 16px;
    border: 1px solid #e0e0e0;
    border-radius: 6px;
    font-family: 'Google Sans', 'Inter', system-ui, sans-serif;
    font-size: 1rem;
    transition: var(--transition-ease);
}

.contact-form input:focus,
.contact-form textarea:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(0, 77, 64, 0.15);
}

.contact-form textarea {
    min-height: 160px;
    resize: vertical;
}

/* Footer */
footer {
    background: linear-gradient(180deg, #181818, var(--dark));
    color: var(--light);
    padding: 64px 0 32px;
    border-top: 4px solid var(--primary);
}

footer .container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 32px;
    text-align: left;
}

footer h4 {
    color: var(--accent);
    border-bottom: 1px solid rgba(255, 179, 0, 0.2);
    padding-bottom: 10px;
    margin-bottom: 20px;
    font-weight: 600;
    font-size: 1.1rem;
}

footer ul {
    list-style: none;
    padding: 0;
}

footer li {
    margin-bottom: 10px;
}

footer a {
    color: rgba(255, 255, 255, 0.85);
    text-decoration: none;
    font-size: 0.95rem;
    transition: var(--transition-ease);
}

footer a:hover {
    color: var(--secondary);
    transform: translateX(3px);
}

.social-links {
    display: flex;
    gap: 12px;
    margin-top: 12px;
}

.social-links a {
    color: var(--light);
    font-size: 1.4rem;
    transition: var(--transition-ease);
}

.social-links a:hover {
    color: var(--accent);
    transform: translateY(-2px);
}

.footer-bottom {
    margin-top: 32px;
    padding-top: 20px;
    border-top: 1px solid rgba(255, 255, 255, 0.15);
    text-align: center;
    grid-column: 1 / -1;
    font-size: 0.85rem;
    color: rgba(255, 255, 255, 0.7);
}

/* Responsive Adjustments */
@media (max-width: 1200px) {
    .container {
        width: 92%;
    }
}

@media (max-width: 992px) {
    .container {
        width: 95%;
        padding: 24px 0;
    }

    .section {
        padding: 64px 0;
    }

    .hero {
        padding: 120px 20px;
    }

    .hero h1 {
        font-size: clamp(2.4rem, 5vw, 4rem);
    }

    .hero p {
        font-size: clamp(1.1rem, 2vw, 1.5rem);
    }
}

@media (max-width: 768px) {
    header .container {
        flex-direction: column;
        gap: 16px;
        text-align: center;
    }

    nav ul {
        flex-direction: column;
        gap: 12px;
    }

    nav a {
        padding: 10px 0;
    }

    .hero {
        padding: 80px 16px;
    }

    .btn-group {
        display: flex;
        flex-direction: column;
        gap: 12px;
    }

    .btn-secondary {
        margin-left: 0;
    }

    .section {
        padding: 48px 0;
    }

    .section h2 {
        font-size: clamp(1.8rem, 4vw, 2.8rem);
    }

    .gallery-grid, .levels-grid, .contact-grid, footer .container {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    .logo {
        font-size: 1.4rem;
    }

    .logo img {
        width: 32px;
        height: 32px;
    }

    .hero {
        padding: 64px 12px;
    }

    .hero h1 {
        font-size: clamp(1.8rem, 6vw, 2.8rem);
    }

    .btn {
        padding: 12px 24px;
        font-size: 1rem;
    }

    .section {
        padding: 32px 0;
    }

    .section h2 {
        font-size: clamp(1.6rem, 5vw, 2.4rem);
    }

    footer {
        padding: 48px 0 24px;
    }
}

/* Accessibility Enhancements */
:focus-visible {
    outline: 3px solid var(--primary);
    outline-offset: 2px;
}

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    border: 0;
}