body {
    margin: 0;
    overflow: hidden;
    background-color: black;
    user-select: none;
    -webkit-user-select: none;
    -ms-user-select: none;
    -webkit-touch-callout: none;
}

canvas {
    position: absolute;
    top: 50%;
    left: 50%;
    background-color: #222;
    transform-origin: center center;
}



button {
    font-size: 24px;
    padding: 10px 20px;
    margin: 10px;
    cursor: pointer;
}

input[type="range"] {
    width: 200px;
}

/* ボタン色 */
.btn-high {
    background-color: red;
    color: white;
}

.btn-middle {
    background-color: green;
    color: white;
}

.btn-low {
    background-color: blue;
    color: white;
}

/* 虹色アニメーション */
@keyframes rainbow {
    0% {
        background-position: 0% 50%;
    }

    50% {
        background-position: 100% 50%;
    }

    100% {
        background-position: 0% 50%;
    }
}

.btn-special {
    background: linear-gradient(270deg, red, orange, yellow, green, blue, indigo, violet);
    background-size: 1400% 1400%;
    animation: rainbow 3s linear infinite;
    color: white;
    font-weight: bold;
    border: 2px solid white;
}