:root {
    --background-color: #f8fafc;
    --text-color: #1e293b;
    --primary-color: #10b981;
    --primary-hover: #059669;
    --white: #ffffff;
    --ball-color: #fbbf24;
    --ball-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
    --surface-color: #ffffff;
    --border-color: #e2e8f0;
    --max-width: 800px;
}

[data-theme="dark"] {
    --background-color: #0f172a;
    --text-color: #f1f5f9;
    --primary-color: #34d399;
    --primary-hover: #10b981;
    --white: #ffffff;
    --ball-color: #f59e0b;
    --ball-shadow: 0 4px 12px rgba(0, 0, 0, 0.4);
    --surface-color: #1e293b;
    --border-color: #334155;
}

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

body {
    font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, system-ui, Roboto, sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    line-height: 1.6;
    transition: background-color 0.3s, color 0.3s;
}

header {
    background: var(--surface-color);
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 2rem;
    position: sticky;
    top: 0;
    z-index: 1000;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--primary-color);
    text-decoration: none;
}

nav {
    display: flex;
    gap: 1.5rem;
    align-items: center;
}

nav a {
    text-decoration: none;
    color: var(--text-color);
    font-weight: 500;
    font-size: 0.95rem;
    transition: color 0.2s;
}

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

main {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 3rem 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 3rem;
}

section {
    width: 100%;
}

.hero {
    text-align: center;
    padding: 2rem 0;
}

.hero h1 {
    font-size: 3rem;
    font-weight: 900;
    margin-bottom: 1.5rem;
    letter-spacing: -1.5px;
    line-height: 1.2;
}

.hero p {
    font-size: 1.1rem;
    opacity: 0.8;
}

.content-card {
    background: var(--surface-color);
    padding: 2.5rem;
    border-radius: 24px;
    box-shadow: 0 4px 20px rgba(0,0,0,0.03);
    border: 1px solid var(--border-color);
}

.prose h2 {
    font-size: 1.75rem;
    margin-bottom: 1.5rem;
    color: var(--primary-color);
}

.prose h3 {
    font-size: 1.25rem;
    margin: 1.5rem 0 0.5rem 0;
}

.prose p {
    margin-bottom: 1rem;
}

.prose ul {
    margin-bottom: 1.5rem;
    padding-left: 1.5rem;
}

.prose li {
    margin-bottom: 0.5rem;
}

footer {
    background: var(--surface-color);
    border-top: 1px solid var(--border-color);
    padding: 4rem 2rem;
    margin-top: 4rem;
    text-align: center;
}

.footer-links {
    display: flex;
    justify-content: center;
    gap: 2rem;
    margin-bottom: 2rem;
}

.footer-links a {
    color: var(--text-color);
    text-decoration: none;
    font-size: 0.9rem;
    opacity: 0.7;
}

.footer-links a:hover {
    opacity: 1;
    color: var(--primary-color);
}

.copyright {
    font-size: 0.85rem;
    opacity: 0.5;
}

#comment-section {
    border-top: 1px solid var(--border-color);
    padding-top: 3rem;
}

theme-toggle {
    display: block;
}

@media (max-width: 650px) {
    .hero h1 {
        font-size: 2.25rem;
    }
    header {
        padding: 1rem;
    }
    nav {
        gap: 1rem;
    }
    .footer-links {
        flex-direction: column;
        gap: 1rem;
    }
}