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

:root {
    --primary-color: #2563eb;
    --secondary-color: #7c3aed;
    --success-color: #10b981;
    --danger-color: #ef4444;
    --warning-color: #f59e0b;
    --light-bg: #f3f4f6;
    --dark-text: #1f2937;
    --light-text: #6b7280;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: var(--dark-text);
    background-color: #ffffff;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Navigation */
.navbar {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

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

.logo h1 {
    font-size: 1.8rem;
    margin-bottom: 0.25rem;
}

.logo .subtitle {
    font-size: 0.9rem;
    opacity: 0.9;
}

.nav-links {
    display: flex;
    list-style: none;
    gap: 2rem;
}

.nav-links a {
    color: white;
    text-decoration: none;
    transition: opacity 0.3s;
    font-weight: 500;
}

.nav-links a:hover {
    opacity: 0.8;
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    padding: 4rem 0;
    text-align: center;
}

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

.hero p {
    font-size: 1.1rem;
    margin-bottom: 0.5rem;
}

.hero .description {
    font-size: 1rem;
    opacity: 0.9;
}

/* About Section */
.about {
    padding: 4rem 0;
    background-color: var(--light-bg);
}

.about h2 {
    text-align: center;
    font-size: 2rem;
    margin-bottom: 3rem;
    color: var(--primary-color);
}

.about-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2rem;
}

.about-box {
    background: white;
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    transition: transform 0.3s, box-shadow 0.3s;
}

.about-box:hover {
    transform: translateY(-5px);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.about-box h3 {
    color: var(--secondary-color);
    margin-bottom: 1rem;
    font-size: 1.3rem;
}

/* Tests Section */
.tests {
    padding: 4rem 0;
}

.tests h2 {
    text-align: center;
    font-size: 2rem;
    margin-bottom: 3rem;
    color: var(--primary-color);
}

.grade-section {
    margin-bottom: 3rem;
}

.grade-section h3 {
    font-size: 1.8rem;
    color: var(--secondary-color);
    margin-bottom: 0.5rem;
}

.grade-description {
    color: var(--light-text);
    margin-bottom: 1.5rem;
    font-size: 0.95rem;
}

.tests-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    gap: 1.5rem;
}

.test-card {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 2rem;
    background: white;
    border: 2px solid var(--light-bg);
    border-radius: 8px;
    text-decoration: none;
    color: var(--dark-text);
    transition: all 0.3s;
    cursor: pointer;
}

.test-card:hover {
    border-color: var(--primary-color);
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.2);
    transform: translateY(-5px);
}

.test-icon {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.test-title {
    font-weight: 600;
    font-size: 1.1rem;
    text-align: center;
    margin-bottom: 0.5rem;
}

.test-desc {
    font-size: 0.85rem;
    color: var(--light-text);
    text-align: center;
}

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

.footer p {
    margin: 0.5rem 0;
}

/* Responsive */
@media (max-width: 768px) {
    .navbar .container {
        flex-direction: column;
        gap: 1rem;
    }

    .nav-links {
        gap: 1rem;
    }

    .hero h2 {
        font-size: 1.8rem;
    }

    .tests-grid {
        grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    }
}