:root {
    --primary: #2563eb;
    --primary-hover: #1d4ed8;
    --bg: #ffffff;
    --text: #1f2937;
    --text-muted: #6b7280;
    --border: #e5e7eb;
    --card-bg: #f9fafb;
    --radius: 8px;
    --shadow: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
}

* {
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    line-height: 1.5;
    margin: 0;
    color: var(--text);
    background-color: var(--bg);
}

header {
    border-bottom: 1px solid var(--border);
    padding: 1rem 2rem;
}

nav .brand {
    font-size: 1.25rem;
    font-weight: 700;
    text-decoration: none;
    color: var(--text);
}

main {
    max-width: 900px;
    margin: 0 auto;
    padding: 4rem 2rem;
}

.hero {
    text-align: center;
    margin-bottom: 4rem;
}

.hero h1 {
    font-size: 3rem;
    font-weight: 800;
    margin-bottom: 1rem;
    letter-spacing: -0.025em;
}

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

.study-list {
    list-style: none;
    padding: 0;
    display: grid;
    gap: 1.5rem;
}

.card {
    display: block;
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 2rem;
    text-decoration: none;
    color: inherit;
    transition: transform 0.2s, box-shadow 0.2s;
}

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

.card h3 {
    margin: 0 0 0.5rem 0;
    font-size: 1.5rem;
    color: var(--primary);
}

.card p {
    margin: 0 0 1rem 0;
    color: var(--text-muted);
}

.cta-text {
    font-weight: 600;
    color: var(--primary);
}

footer {
    text-align: center;
    padding: 4rem 2rem;
    color: var(--text-muted);
    font-size: 0.875rem;
    border-top: 1px solid var(--border);
}

@media (max-width: 640px) {
    .hero h1 {
        font-size: 2.25rem;
    }
}