:root {
    --bg-gradient: linear-gradient(135deg, #1a1a2e 0%, #16213e 50%, #0f3460 100%);
    --text-color: #ffffff;
    --accent-color: #e94560;
    --card-bg: rgba(255, 255, 255, 0.05);
    --card-border: rgba(255, 255, 255, 0.1);
    --header-bg: rgba(22, 33, 62, 0.8);
    --footer-bg: #16213e;
    --number-bg: #e94560;
    --number-text: #fff;
    --btn-bg: #e94560;
    --btn-hover: #c62842;
}

body.light-mode {
    --bg-gradient: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
    --text-color: #333;
    --accent-color: #2196F3;
    --card-bg: #ffffff;
    --card-border: #e0e0e0;
    --header-bg: rgba(255, 255, 255, 0.9);
    --footer-bg: #ffffff;
    --number-bg: #2196F3;
    --number-text: #fff;
    --btn-bg: #2196F3;
    --btn-hover: #1976D2;
}

body {
    background: var(--bg-gradient);
    color: var(--text-color);
    font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, system-ui, Roboto, sans-serif;
    margin: 0;
    padding: 0;
    line-height: 1.6;
    transition: all 0.3s ease;
}

.container {
    max-width: 800px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
header {
    background: var(--header-bg);
    backdrop-filter: blur(10px);
    position: sticky;
    top: 0;
    z-index: 1000;
    border-bottom: 1px solid var(--card-border);
    padding: 1rem 0;
}

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

header h1 {
    font-size: 1.5rem;
    margin: 0;
    color: var(--accent-color);
}

#theme-toggle {
    padding: 0.5rem 1rem;
    border-radius: 20px;
    border: 1px solid var(--accent-color);
    background: transparent;
    color: var(--accent-color);
    cursor: pointer;
    font-weight: bold;
    font-size: 0.8rem;
}

/* Main Content */
main {
    padding: 3rem 0;
}

section {
    margin-bottom: 3rem;
}

.card {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: 1.5rem;
    padding: 2.5rem;
    box-shadow: 0 10px 30px rgba(0,0,0,0.1);
}

.content-section h2 {
    color: var(--accent-color);
    margin-top: 0;
}

.content-section ul {
    padding-left: 1.2rem;
}

.content-section li {
    margin-bottom: 0.5rem;
}

/* Footer */
footer {
    background: var(--footer-bg);
    border-top: 1px solid var(--card-border);
    padding: 3rem 0;
    text-align: center;
    color: var(--text-color);
    opacity: 0.8;
}

.footer-links {
    margin-top: 1rem;
}

.footer-links a {
    color: var(--text-color);
    text-decoration: none;
    margin: 0 1rem;
    font-size: 0.9rem;
}

.footer-links a:hover {
    text-decoration: underline;
    color: var(--accent-color);
}

/* Comment Section */
.comment-section {
    background: var(--card-bg);
    border-radius: 1.5rem;
    padding: 1rem;
}

/* Responsive */
@media (max-width: 600px) {
    header h1 { font-size: 1.2rem; }
    .card { padding: 1.5rem; }
}