:root {
    --bg: #f0f0f0;
    --container-bg: #ffffff;
    --text: #333333;
    --shadow: rgba(0, 0, 0, 0.1);
    --ball-bg: #007bff;
    --ball-color: #ffffff;
    --btn-bg: #007bff;
    --btn-color: #ffffff;
    --theme-btn-bg: #e0e0e0;
    --theme-btn-color: #333333;
}

body.dark {
    --bg: #1a1a2e;
    --container-bg: #16213e;
    --text: #e0e0e0;
    --shadow: rgba(0, 0, 0, 0.5);
    --ball-bg: #4a9eff;
    --ball-color: #ffffff;
    --btn-bg: #4a9eff;
    --btn-color: #ffffff;
    --theme-btn-bg: #2d2d4e;
    --theme-btn-color: #e0e0e0;
}

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

.theme-btn {
    position: fixed;
    top: 1rem;
    right: 1rem;
    padding: 0.5rem 0.75rem;
    font-size: 1.2rem;
    cursor: pointer;
    border: none;
    background-color: var(--theme-btn-bg);
    color: var(--theme-btn-color);
    border-radius: 50px;
    box-shadow: 0 2px 6px var(--shadow);
    transition: background-color 0.3s, transform 0.1s;
    z-index: 100;
}

.theme-btn:hover {
    transform: scale(1.1);
}

.container {
    text-align: center;
    padding: 2rem;
    background-color: var(--container-bg);
    border-radius: 10px;
    box-shadow: 0 0 10px var(--shadow);
    transition: background-color 0.3s, box-shadow 0.3s;
}

button#generate {
    padding: 0.5rem 1rem;
    font-size: 1rem;
    cursor: pointer;
    border: none;
    background-color: var(--btn-bg);
    color: var(--btn-color);
    border-radius: 5px;
    margin-top: 1rem;
    transition: background-color 0.3s;
}

#numbers {
    margin-top: 2rem;
    font-size: 1.5rem;
    display: flex;
    justify-content: center;
    gap: 1rem;
    flex-wrap: wrap;
}

#numbers span {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 2.5rem;
    height: 2.5rem;
    border-radius: 50%;
    background-color: var(--ball-bg);
    color: var(--ball-color);
    font-weight: bold;
    font-size: 1rem;
    transition: background-color 0.3s;
}