:root {
    --bg-color: #f8f9fa;
    --container-bg: #ffffff;
    --text-color: #212529;
    --text-muted: #6c757d;
    --number-bg: #ffffff;
    --number-border: #dee2e6;
    --button-bg: #007bff;
    --button-hover: #0056b3;
    --button-text: #ffffff;
    --nav-bg: #ffffff;
    --footer-bg: #343a40;
    --footer-text: #ffffff;
}

body.dark-mode {
    --bg-color: #121212;
    --container-bg: #1e1e1e;
    --text-color: #e9ecef;
    --text-muted: #adb5bd;
    --number-bg: #2d2d2d;
    --number-border: #444;
    --button-bg: #375a7f;
    --button-hover: #2b4764;
    --nav-bg: #1e1e1e;
}

* {
    box-sizing: border-box;
}

body {
    font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    margin: 0;
    padding: 0;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    transition: background-color 0.3s, color 0.3s;
}

header {
    background-color: var(--nav-bg);
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    position: sticky;
    top: 0;
    z-index: 1000;
}

.nav-container {
    max-width: 1000px;
    margin: 0 auto;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.5rem;
    font-weight: bold;
    text-decoration: none;
    color: var(--button-bg);
}

.nav-links {
    list-style: none;
    display: flex;
    margin: 0;
    padding: 0;
}

.nav-links li {
    margin-left: 20px;
}

.nav-links a {
    text-decoration: none;
    color: var(--text-color);
    font-weight: 500;
}

.nav-links a:hover {
    color: var(--button-bg);
}

.container {
    max-width: 800px;
    margin: 2rem auto;
    padding: 0 2rem;
}

section {
    padding: 3rem 0;
}

.hero-section {
    text-align: center;
}

h1 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.subtitle {
    color: var(--text-muted);
    font-size: 1.2rem;
    margin-bottom: 2rem;
}

.numbers {
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 15px;
    margin-bottom: 2rem;
}

.number {
    width: 60px;
    height: 60px;
    border-radius: 50%;
    background-color: var(--number-bg);
    border: 3px solid var(--number-border);
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.5rem;
    font-weight: bold;
    box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}

.main-btn {
    padding: 12px 30px;
    font-size: 1.2rem;
    font-weight: bold;
    background-color: var(--button-bg);
    color: var(--button-text);
    border: none;
    border-radius: 50px;
    cursor: pointer;
    transition: transform 0.2s, background-color 0.2s;
}

.main-btn:hover {
    background-color: var(--button-hover);
    transform: translateY(-2px);
}

.content-section h2 {
    border-left: 5px solid var(--button-bg);
    padding-left: 15px;
    margin-bottom: 1.5rem;
}

hr {
    border: 0;
    height: 1px;
    background: var(--number-border);
    margin: 2rem 0;
}

.contact-section {
    background-color: var(--container-bg);
    padding: 2rem;
    border-radius: 10px;
    box-shadow: 0 4px 10px rgba(0,0,0,0.05);
}

.form-group {
    margin-bottom: 1.5rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: bold;
}

.form-group input, .form-group textarea {
    width: 100%;
    padding: 12px;
    border: 1px solid var(--number-border);
    border-radius: 5px;
    background-color: var(--bg-color);
    color: var(--text-color);
}

.submit-btn {
    width: 100%;
    padding: 12px;
    background-color: var(--button-bg);
    color: var(--button-text);
    border: none;
    border-radius: 5px;
    font-weight: bold;
    cursor: pointer;
}

footer {
    background-color: var(--footer-bg);
    color: var(--footer-text);
    text-align: center;
    padding: 2rem 0;
    margin-top: 5rem;
}

#theme-toggle {
    padding: 8px 15px;
    background: transparent;
    border: 1px solid var(--button-bg);
    color: var(--button-bg);
    border-radius: 5px;
    cursor: pointer;
}

#theme-toggle:hover {
    background: var(--button-bg);
    color: var(--button-text);
}

.privacy-policy {
    font-size: 0.9rem;
    color: var(--text-muted);
}