:root {
    --bg-color: #f0f0f0;
    --container-bg: transparent;
    --text-color: #333;
    --number-bg: #fff;
    --number-text: #333;
    --btn-bg: #007bff;
    --btn-hover: #0056b3;
}

body.dark-mode {
    --bg-color: #121212;
    --text-color: #e0e0e0;
    --number-bg: #333;
    --number-text: #fff;
    --btn-bg: #3700b3;
    --btn-hover: #6200ee;
}

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

.container {
    text-align: center;
}

.numbers {
    display: flex;
    justify-content: center;
    margin: 2rem 0;
}

.number {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background-color: var(--number-bg);
    color: var(--number-text);
    margin: 0 0.5rem;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.2rem;
    font-weight: bold;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.2);
    transition: background-color 0.3s, color 0.3s;
}

button {
    padding: 0.8rem 2rem;
    font-size: 1rem;
    border: none;
    border-radius: 8px;
    background-color: var(--btn-bg);
    color: #fff;
    cursor: pointer;
    transition: background-color 0.3s, transform 0.1s;
}

button:hover {
    background-color: var(--btn-hover);
}

button:active {
    transform: scale(0.98);
}

/* Theme Toggle Button Style */
.theme-btn {
    position: fixed;
    top: 20px;
    right: 20px;
    padding: 10px;
    width: 45px;
    height: 45px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    background-color: var(--number-bg);
    color: var(--text-color);
    box-shadow: 0 4px 10px rgba(0,0,0,0.2);
    z-index: 1000;
}