:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --bg: #f5f7fb;
    --text: #111827;
    --muted: #6b7280;
    --card-bg: #ffffff;
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    color: var(--text);
    background: linear-gradient(135deg, #f8fafc 0%, #e0e7ff 100%);
}

.top-bar {
    display: flex;
    justify-content: flex-end;
    padding: 24px;
}

.login-button {
    padding: 12px 24px;
    border-radius: 999px;
    background: var(--primary);
    color: #fff;
    text-decoration: none;
    font-weight: 600;
    box-shadow: 0 10px 30px rgba(37, 99, 235, 0.25);
    transition: transform 0.2s ease, box-shadow 0.2s ease, background 0.2s ease;
}

.login-button:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 16px 32px rgba(37, 99, 235, 0.35);
}

main {
    max-width: 960px;
    margin: 0 auto 80px;
    padding: 0 24px 80px;
}

.hero {
    text-align: center;
    margin-bottom: 48px;
    padding: 24px 0 8px;
}

.hero h1 {
    font-size: clamp(2.25rem, 5vw, 3.25rem);
    font-weight: 700;
    margin-bottom: 20px;
    line-height: 1.15;
    color: #0f172a;
}

.hero p {
    font-size: clamp(1.05rem, 2vw, 1.3rem);
    color: var(--muted);
    margin: 0 auto;
    max-width: 720px;
    line-height: 1.6;
}

.toc-card {
    background: rgba(255, 255, 255, 0.85);
    backdrop-filter: blur(10px);
    border-radius: 24px;
    padding: 32px;
    margin-bottom: 40px;
    box-shadow: 0 24px 60px rgba(15, 23, 42, 0.12);
}

.toc-card h2 {
    margin-top: 0;
    font-size: 1.5rem;
    margin-bottom: 20px;
}

.toc-list {
    list-style: none;
    padding: 0;
    margin: 0;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 12px 24px;
}

.toc-list a {
    text-decoration: none;
    color: var(--primary-dark);
    font-weight: 600;
    display: inline-flex;
    align-items: center;
    gap: 10px;
    padding: 10px 14px;
    border-radius: 12px;
    background: rgba(37, 99, 235, 0.08);
    transition: background 0.2s ease, transform 0.2s ease;
}

.toc-list a:hover {
    background: rgba(37, 99, 235, 0.18);
    transform: translateX(4px);
}

section {
    background: rgba(255, 255, 255, 0.93);
    backdrop-filter: blur(6px);
    border-radius: 24px;
    padding: 40px;
    margin-bottom: 32px;
    box-shadow: 0 20px 50px rgba(30, 41, 59, 0.12);
}

section h3 {
    margin-top: 0;
    font-size: 1.75rem;
    margin-bottom: 18px;
}

section p {
    line-height: 1.7;
    font-size: 1.05rem;
    color: #1f2937;
}

section ul {
    padding-left: 20px;
    line-height: 1.7;
    color: #1f2937;
}

.highlight {
    background: rgba(37, 99, 235, 0.1);
    border-left: 4px solid var(--primary);
    padding: 16px 20px;
    border-radius: 12px;
    margin: 20px 0;
    color: #1e293b;
}

@media (max-width: 640px) {
    .top-bar {
        justify-content: center;
    }

    section {
        padding: 28px 24px;
    }
}