:root {
    --bg-color: #f0f2f5;
    --card-bg: white;
    --text-primary: #1a1a1a;
    --text-secondary: #666;
    --input-border: #ddd;
    --accent-color: #007bff;
    --accent-hover: #0056b3;
    --result-bg: #e7f3ff;
    --result-text: #0056b3;
}

[data-theme="dark"] {
    --bg-color: #121212;
    --card-bg: #1e1e1e;
    --text-primary: #f0f2f5;
    --text-secondary: #b0b0b0;
    --input-border: #333;
    --result-bg: #1a2a3a;
    --result-text: #66b2ff;
}

body {
    font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, system-ui, Roboto, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    transition: background-color 0.3s, color 0.3s;
}

.container {
    background-color: var(--card-bg);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    text-align: center;
    width: 100%;
    max-width: 400px;
    position: relative;
    transition: background-color 0.3s;
}

.theme-toggle {
    position: absolute;
    top: 1rem;
    right: 1rem;
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    padding: 5px;
    border-radius: 50%;
    transition: background-color 0.2s;
}

.theme-toggle:hover {
    background-color: rgba(0, 0, 0, 0.05);
}

[data-theme="dark"] .theme-toggle:hover {
    background-color: rgba(255, 255, 255, 0.1);
}

h1 {
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

p {
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
}

form {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

input {
    padding: 12px;
    border: 1px solid var(--input-border);
    border-radius: 8px;
    font-size: 1rem;
    outline: none;
    background-color: var(--card-bg);
    color: var(--text-primary);
    transition: border-color 0.2s, background-color 0.3s, color 0.3s;
}

input:focus {
    border-color: var(--accent-color);
}

button[type="submit"] {
    padding: 12px;
    background-color: var(--accent-color);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    cursor: pointer;
    transition: background-color 0.2s;
}

button[type="submit"]:hover {
    background-color: var(--accent-hover);
}

.hidden {
    display: none;
}

#result-message {
    margin-top: 20px;
    padding: 10px;
    background-color: var(--result-bg);
    border-radius: 8px;
    color: var(--result-text);
    font-weight: bold;
    transition: background-color 0.3s, color 0.3s;
}