:root {
    --primary-color: #4a90e2;
    --secondary-color: #f5a623;
    --background-color: #f0f2f5;
    --container-bg: #fff;
    --text-color: #333;
    --text-secondary: #666;
    --white: #fff;
    --shadow-color: rgba(0, 0, 0, 0.1);
    --header-bg: #fff;
}

body.dark-mode {
    --background-color: #121212;
    --container-bg: #1e1e1e;
    --text-color: #e0e0e0;
    --text-secondary: #aaa;
    --shadow-color: rgba(0, 0, 0, 0.5);
    --primary-color: #64b5f6;
    --header-bg: #1e1e1e;
}

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

.main-header {
    background-color: var(--header-bg);
    box-shadow: 0 2px 4px var(--shadow-color);
    padding: 10px 20px;
    position: sticky;
    top: 0;
    z-index: 1000;
}

.nav-container {
    max-width: 800px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 20px;
    font-weight: bold;
    color: var(--primary-color);
}

.container {
    max-width: 800px;
    margin: 40px auto;
    background-color: var(--container-bg);
    padding: 40px;
    border-radius: 12px;
    box-shadow: 0 10px 20px var(--shadow-color);
    transition: background-color 0.3s, box-shadow 0.3s;
}

.generator-section {
    text-align: center;
    padding: 20px 0;
}

.subtitle {
    color: var(--text-secondary);
    margin-bottom: 30px;
}

.info-section {
    text-align: left;
    padding: 20px 0;
}

.info-section h2 {
    color: var(--primary-color);
    font-size: 1.5rem;
    margin-top: 30px;
}

.section-desc {
    color: var(--text-secondary);
    margin-bottom: 20px;
}

.divider {
    margin: 40px 0;
    border: 0;
    border-top: 1px solid var(--shadow-color);
}

.contact-section h2, .comments-section h2 {
    color: var(--primary-color);
    margin-bottom: 20px;
    text-align: center;
}

.form-group {
    text-align: left;
    margin-bottom: 15px;
}

.form-group label {
    display: block;
    margin-bottom: 5px;
    font-size: 14px;
    font-weight: 600;
}

.form-group input,
.form-group textarea {
    width: 100%;
    padding: 12px;
    border: 1px solid var(--shadow-color);
    border-radius: 8px;
    background-color: var(--background-color);
    color: var(--text-color);
    font-size: 14px;
    box-sizing: border-box;
}

.form-group textarea {
    height: 120px;
    resize: vertical;
}

#submit-btn {
    width: 100%;
    background-color: var(--secondary-color);
    color: var(--white);
    border: none;
    padding: 14px;
    font-size: 16px;
    font-weight: bold;
    border-radius: 8px;
    cursor: pointer;
    transition: transform 0.2s, opacity 0.3s;
}

#submit-btn:hover {
    opacity: 0.9;
    transform: translateY(-2px);
}

#theme-toggle {
    background: none;
    border: 1px solid var(--primary-color);
    color: var(--primary-color);
    padding: 6px 12px;
    border-radius: 6px;
    cursor: pointer;
    font-size: 14px;
    transition: all 0.3s;
}

#theme-toggle:hover {
    background-color: var(--primary-color);
    color: var(--white);
}

h1 {
    color: var(--primary-color);
    font-size: 2.5rem;
    margin-bottom: 10px;
}

#generate-btn {
    background-color: var(--primary-color);
    color: var(--white);
    border: none;
    padding: 18px 40px;
    font-size: 18px;
    font-weight: bold;
    border-radius: 10px;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

#generate-btn:hover {
    background-color: #357abd;
    transform: scale(1.05);
}

#numbers-container {
    margin-top: 40px;
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 15px;
}

.number {
    width: 60px;
    height: 60px;
    background-color: var(--secondary-color);
    color: var(--white);
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 28px;
    font-weight: bold;
    border-radius: 50%;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
    animation: popIn 0.3s ease-out forwards;
}

@keyframes popIn {
    0% { transform: scale(0); opacity: 0; }
    100% { transform: scale(1); opacity: 1; }
}

.main-footer {
    text-align: center;
    padding: 40px 20px;
    color: var(--text-secondary);
    font-size: 14px;
}

.footer-nav {
    margin-top: 10px;
}

.footer-nav a {
    color: var(--text-secondary);
    text-decoration: none;
    margin: 0 10px;
}

.footer-nav a:hover {
    text-decoration: underline;
}

@media (max-width: 600px) {
    .container {
        padding: 20px;
        margin: 20px 10px;
    }
    h1 { font-size: 2rem; }
    .number { width: 50px; height: 50px; font-size: 22px; }
}