:root {
    --bg-color: #ffffff;
    --text-color: #333333;
    --toggle-bg: #e0e0e0;
    --toggle-btn: #ffffff;
    --input-bg: #f9f9f9;
    --input-border: #dddddd;
    --primary-color: #007bff;
    --secondary-color: #6c757d;
    --transition-speed: 0.3s;
    --container-max-width: 800px;
}

body.dark-mode {
    --bg-color: #1a1a1a;
    --text-color: #f0f0f0;
    --toggle-bg: #444444;
    --toggle-btn: #2a2a2a;
    --input-bg: #2d2d2d;
    --input-border: #444444;
}

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

.nav-container {
    width: 100%;
    border-bottom: 1px solid var(--input-border);
    padding: 1rem 0;
}

nav {
    max-width: var(--container-max-width);
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 20px;
}

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

.nav-links {
    display: flex;
    gap: 20px;
    align-items: center;
}

.nav-links a {
    text-decoration: none;
    color: var(--text-color);
    font-size: 0.9rem;
    font-weight: 500;
    opacity: 0.8;
    transition: opacity 0.2s;
}

.nav-links a:hover {
    opacity: 1;
}

.theme-toggle {
    cursor: pointer;
    padding: 6px 12px;
    border-radius: 20px;
    border: none;
    background-color: var(--toggle-bg);
    color: var(--text-color);
    font-size: 0.8rem;
    font-weight: 600;
    display: inline-flex;
    align-items: center;
    gap: 6px;
}

.container {
    max-width: var(--container-max-width);
    margin: 40px auto;
    padding: 0 20px;
}

h1, h2, h3 {
    margin-top: 2rem;
}

.hero {
    text-align: center;
    padding: 60px 20px;
    background: linear-gradient(135deg, rgba(0,123,255,0.05) 0%, rgba(0,123,255,0) 100%);
    border-radius: 24px;
    margin-bottom: 40px;
}

.hero h1 {
    font-size: 3rem;
    margin-bottom: 1rem;
    margin-top: 0;
}

.hero p {
    font-size: 1.2rem;
    opacity: 0.8;
}

.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 24px;
    margin: 40px 0;
}

.card {
    border: 1px solid var(--input-border);
    padding: 24px;
    border-radius: 16px;
    transition: transform 0.2s, box-shadow 0.2s;
}

.card:hover {
    transform: translateY(-4px);
    box-shadow: 0 10px 20px rgba(0,0,0,0.05);
}

.card h3 {
    margin-top: 0;
}

footer {
    text-align: center;
    padding: 60px 20px;
    border-top: 1px solid var(--input-border);
    margin-top: 80px;
    opacity: 0.6;
    font-size: 0.8rem;
}

/* Form Styles */
.contact-form {
    text-align: left;
    background-color: transparent;
    padding: 2rem;
    border-radius: 12px;
    border: 1px solid var(--input-border);
    width: 100%;
    box-sizing: border-box;
}

.form-group {
    margin-bottom: 1.2rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
}

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

.submit-btn {
    width: 100%;
    padding: 14px;
    border-radius: 8px;
    border: none;
    background-color: var(--primary-color);
    color: white;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
}