/* CSS Variables */
:root {
    --primary-color: #2563eb;
    --primary-dark: #1d4ed8;
    --secondary-color: #10b981;
    --accent-color: #f59e0b;
    --text-color: #1f2937;
    --text-light: #6b7280;
    --background: #ffffff;
    --background-alt: #f9fafb;
    --border-color: #e5e7eb;
    --primary-level: #8b5cf6;
    --form-level: #2563eb;
    --secondary-level: #10b981;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --radius: 8px;
    --radius-lg: 16px;
}

/* Reset and Base Styles */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
    color: var(--text-color);
    background-color: var(--background);
    line-height: 1.6;
}

a {
    text-decoration: none;
    color: inherit;
}

ul {
    list-style: none;
}

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

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

/* Header & Navigation */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: var(--background);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
}

.nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 70px;
}

.logo h1 {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

.nav-links {
    display: flex;
    gap: 2rem;
}

.nav-links a {
    font-weight: 500;
    color: var(--text-color);
    transition: color 0.2s ease;
}

.nav-links a:hover {
    color: var(--primary-color);
}

.mobile-menu-btn {
    display: none;
    flex-direction: column;
    justify-content: space-around;
    width: 24px;
    height: 20px;
    background: transparent;
    border: none;
    cursor: pointer;
}

.mobile-menu-btn span {
    width: 100%;
    height: 2px;
    background-color: var(--text-color);
    transition: all 0.3s ease;
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius);
    font-weight: 600;
    font-size: 1rem;
    transition: all 0.2s ease;
    cursor: pointer;
    border: none;
    text-align: center;
}

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

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

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

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

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

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

.btn-large {
    padding: 1rem 2rem;
    font-size: 1.125rem;
}

.btn-disabled {
    background-color: var(--border-color);
    color: var(--text-light);
    cursor: not-allowed;
    opacity: 0.7;
}

/* Hero Section */
.hero {
    padding: 10rem 0 6rem;
    background: linear-gradient(135deg, #eff6ff 0%, #f0fdf4 100%);
    text-align: center;
}

.hero-content h2 {
    font-size: 3rem;
    font-weight: 800;
    margin-bottom: 1.5rem;
    color: var(--text-color);
}

.hero-content p {
    font-size: 1.25rem;
    color: var(--text-light);
    max-width: 600px;
    margin: 0 auto 2rem;
}

.hero-buttons {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
}

/* Section Titles */
.section-title {
    font-size: 2.25rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: 3rem;
}

/* Features Section */
.features {
    padding: 6rem 0;
    background-color: var(--background);
}

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

.feature-card {
    padding: 2rem;
    background: var(--background);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    text-align: center;
    transition: all 0.3s ease;
}

.feature-card:hover {
    box-shadow: var(--shadow-lg);
    transform: translateY(-4px);
}

.feature-icon {
    width: 60px;
    height: 60px;
    margin: 0 auto 1.5rem;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    border-radius: 50%;
    padding: 14px;
}

.feature-icon svg {
    width: 100%;
    height: 100%;
    stroke: white;
}

.feature-card h3 {
    font-size: 1.25rem;
    margin-bottom: 0.75rem;
}

.feature-card p {
    color: var(--text-light);
}

/* Levels Section */
.levels {
    padding: 6rem 0;
    background-color: var(--background-alt);
}

.levels-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.level-card {
    background: var(--background);
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow);
    transition: all 0.3s ease;
}

.level-card:hover {
    box-shadow: var(--shadow-lg);
    transform: translateY(-4px);
}

.level-card.featured {
    border: 2px solid var(--primary-color);
}

.level-header {
    padding: 1.5rem;
    text-align: center;
    color: white;
}

.level-header h3 {
    font-size: 1.5rem;
    margin-bottom: 0.25rem;
}

.level-header span {
    opacity: 0.9;
}

.primary-level {
    background: linear-gradient(135deg, var(--primary-level), #a78bfa);
}

.form-level {
    background: linear-gradient(135deg, var(--form-level), #3b82f6);
}

.secondary-level {
    background: linear-gradient(135deg, var(--secondary-level), #34d399);
}

.level-subjects {
    padding: 1.5rem;
}

.level-subjects li {
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--border-color);
    color: var(--text-light);
}

.level-subjects li:last-child {
    border-bottom: none;
}

.level-card .btn {
    display: block;
    margin: 1rem 1.5rem 1.5rem;
}

/* Subjects Section */
.subjects {
    padding: 6rem 0;
    background-color: var(--background);
}

.subjects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 1.5rem;
}

.subject-card {
    padding: 1.5rem;
    background: var(--background);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    text-align: center;
    transition: all 0.3s ease;
}

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

.subject-icon {
    width: 60px;
    height: 60px;
    margin: 0 auto 1rem;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    font-weight: 700;
    color: white;
}

.subject-icon.math {
    background: linear-gradient(135deg, #3b82f6, #2563eb);
}

.subject-icon.science {
    background: linear-gradient(135deg, #10b981, #059669);
}

.subject-icon.english {
    background: linear-gradient(135deg, #f59e0b, #d97706);
}

.subject-icon.biology {
    background: linear-gradient(135deg, #22c55e, #16a34a);
}

.subject-icon.chemistry {
    background: linear-gradient(135deg, #8b5cf6, #7c3aed);
}

.subject-icon.physics {
    background: linear-gradient(135deg, #ef4444, #dc2626);
}

.subject-card h4 {
    font-size: 1rem;
    color: var(--text-color);
}

/* CTA Section */
.cta {
    padding: 6rem 0;
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    text-align: center;
    color: white;
}

.cta h2 {
    font-size: 2.25rem;
    margin-bottom: 1rem;
}

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

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

.cta .btn-primary:hover {
    background-color: var(--background-alt);
}

/* Download App Section */
.download-app {
    padding: 6rem 0;
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    text-align: center;
    color: white;
}

.download-app .section-title {
    color: white;
}

.download-subtitle {
    font-size: 1.125rem;
    opacity: 0.9;
    max-width: 600px;
    margin: 0 auto 2.5rem;
}

.download-features {
    display: flex;
    justify-content: center;
    gap: 3rem;
    margin-bottom: 3rem;
    flex-wrap: wrap;
}

.download-feature {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.75rem;
}

.download-feature svg {
    width: 40px;
    height: 40px;
    stroke: white;
}

.download-feature span {
    font-weight: 500;
    opacity: 0.95;
}

.download-buttons {
    display: flex;
    justify-content: center;
    gap: 1.5rem;
    flex-wrap: wrap;
    margin-bottom: 2rem;
}

.download-btn {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius);
    font-weight: 600;
    transition: all 0.2s ease;
    cursor: pointer;
    text-decoration: none;
}

.download-btn svg {
    width: 32px;
    height: 32px;
}

.download-btn-text {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    text-align: left;
}

.download-btn-small {
    font-size: 0.7rem;
    font-weight: 400;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    opacity: 0.9;
}

.download-btn-large {
    font-size: 1.125rem;
    font-weight: 600;
    line-height: 1.2;
}

.download-btn.google-play {
    background-color: #000;
    color: white;
}

.download-btn.google-play:hover {
    background-color: #333;
}

.download-btn.google-play svg {
    fill: white;
}

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

.download-btn.apk-download:hover {
    background-color: var(--background-alt);
}

.download-btn.apk-download svg {
    stroke: var(--primary-color);
}

.download-note {
    font-size: 0.875rem;
    opacity: 0.8;
}

/* Contact Section */
.contact {
    padding: 6rem 0;
    background-color: var(--background-alt);
}

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

.contact-content > p {
    color: var(--text-light);
    margin-bottom: 2rem;
}

.contact-info {
    display: flex;
    justify-content: center;
    gap: 2rem;
    flex-wrap: wrap;
}

.contact-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    color: var(--text-color);
}

.contact-item svg {
    width: 24px;
    height: 24px;
    stroke: var(--primary-color);
}

/* Footer */
.footer {
    background-color: var(--text-color);
    color: white;
    padding: 4rem 0 2rem;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 3rem;
    margin-bottom: 3rem;
}

.footer-brand h3 {
    font-size: 1.5rem;
    margin-bottom: 0.75rem;
}

.footer-brand p {
    color: #9ca3af;
}

.footer-links h4 {
    margin-bottom: 1rem;
}

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

.footer-links a {
    color: #9ca3af;
    transition: color 0.2s ease;
}

.footer-links a:hover {
    color: white;
}

.footer-bottom {
    padding-top: 2rem;
    border-top: 1px solid #374151;
    text-align: center;
}

.footer-bottom p {
    color: #9ca3af;
}

/* Mobile Styles */
@media (max-width: 768px) {
    .nav-links {
        position: absolute;
        top: 70px;
        left: 0;
        right: 0;
        background: var(--background);
        flex-direction: column;
        padding: 1.5rem;
        gap: 1rem;
        border-bottom: 1px solid var(--border-color);
        display: none;
    }

    .nav-links.active {
        display: flex;
    }

    .mobile-menu-btn {
        display: flex;
    }

    .mobile-menu-btn.active span:nth-child(1) {
        transform: rotate(45deg) translate(5px, 5px);
    }

    .mobile-menu-btn.active span:nth-child(2) {
        opacity: 0;
    }

    .mobile-menu-btn.active span:nth-child(3) {
        transform: rotate(-45deg) translate(5px, -5px);
    }

    .hero {
        padding: 8rem 0 4rem;
    }

    .hero-content h2 {
        font-size: 2rem;
    }

    .hero-content p {
        font-size: 1rem;
    }

    .section-title {
        font-size: 1.75rem;
    }

    .features, .levels, .subjects, .contact {
        padding: 4rem 0;
    }

    .cta {
        padding: 4rem 0;
    }

    .cta h2 {
        font-size: 1.75rem;
    }

    .download-app {
        padding: 4rem 0;
    }

    .download-features {
        gap: 1.5rem;
    }

    .download-buttons {
        gap: 1rem;
    }
}

@media (max-width: 480px) {
    .hero-buttons {
        flex-direction: column;
        align-items: center;
    }

    .hero-buttons .btn {
        width: 100%;
        max-width: 280px;
    }

    .levels-grid {
        grid-template-columns: 1fr;
    }

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

    .download-buttons {
        flex-direction: column;
        align-items: center;
    }

    .download-btn {
        width: 100%;
        max-width: 280px;
        justify-content: center;
    }

    .download-features {
        flex-direction: column;
        gap: 1.25rem;
    }
}