body, html {
    margin: 0;
    padding: 0;
    width: 100%;
    height: 100%;
    overflow: hidden;
    background-color: rgb(0, 0, 0);
    font-family: sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
}

.screen {
    display: none;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    width: 100%;
    height: 100%;
    text-align: center;
    color: white;
}

.screen.active {
    display: flex;
}

canvas {
    background-color: rgb(0, 0, 0); /* 落ちる領域の色 */
    display: block;
    touch-action: none; /* スマホでのスワイプスクロールを防ぐ */
}

button {
    font-size: 1.2rem;
    padding: 10px 20px;
    margin: 10px;
    cursor: pointer;
    border: none;
    border-radius: 5px;
    background-color: #4CAF50;
    color: white;
}

h1 {
    font-size: 2.5rem;
}

h2 {
    font-size: 2rem;
}