style.css

* {
    box-sizing: border-box
}

body {
    margin:10;
    background-color: azure;
    transition: background-color .5s;
}


body.dark {
    background-color: blue;
}

body.glow {
    background-color: whitesmoke;
}

.box{
    height: 200px;
    width:200px;
    background-color: lightsteelblue;
    border:1px solid;
    animation: spin 10s infinite linear;
    animation-play-state: paused;
    transition: background-color 1s, box-shadow 1s;
}

.box.dark {
    background-color: gray;
}

.box.glow {
    background-color: greenyellow;
    box-shadow: 0 0 30px 15px deeppink;
}

.box.spin {
    animation-play-state: running;
}

.flex {
    display: flex;
    justify-content: space-evenly;
    margin-top:100px;
}
  
button {
    padding: 10px;
    border:1px solid;
    cursor:pointer;
    background-color: thistle;
    border-radius:5px;
    transition: background-color .2s;
}

button:hover {
    background-color: pink;
}
button:active {
    background-color: white;
}

.chair {
    width: 200px;
    position:fixed;
    bottom: 10px;
    right: 10px;
    opacity:0;
    transition: opacity  1s;
}

.draggable {
    cursor:grab;
}

@keyframes spin {
    0% {
        transform: rotate(0);
    }
    100% {
        transform: rotate(360deg);
    }
}