.grid {
    position: absolute;
    width: 560px;
    height: 300px;
    border: 2px solid black;
    margin: 100px auto;
    background-image: url('galaxy.jpg');
}

.user {
    position: absolute;
    width: 100px;
    height: 20px;
    background-color: blueviolet;
}

.block {
    position: absolute;
    width: 100px;
    height: 20px;
    background-color: cyan;
}

.ball {
    position: absolute;
    width: 20px;
    height: 20px;
    border-radius: 10px;
    background-color: white;
}

#start-btn {
    display: flex;
    margin: 0.5px;
    padding: 10px;
    background-color: purple;
    color: white;
    border: none;
    border-radius: 10px;
    cursor: pointer;
    font-size: 16px;
}