:root{
    --width: 400px;
    --boardWidth: 500px;
}
*{
    padding: 0;
    margin: 0;
    outline: none;
    overflow-x: hidden;
}
.game{
    width: var(--boardWidth);
    height: 500px;
    margin:auto;
    border: 5px solid white;
}

.slider{
    visibility: hidden;
    background: url(tati.png);
    height: 20px;
    width: 100px;
    position: relative;
}
#slider1{
    visibility: visible;
}
.animate{
    animation: side 4s infinite linear;
}
@keyframes side{
    0%{left:0px}
    50%{left:var(--width)}
    100%{left:0px}
}


button{
    font-size: 2rem;
    padding: 0.5rem 2rem;
    border: 3px solid white;
    border-radius: 0.3rem;
    margin: 1rem auto;
    display: block;
}
#btn{
    background-color: black;
}
#restart{
    background-color: red;
    display: none;
}
#btn:hover, #restart:hover{
    background-color: gray; 
}
#btn:active, #restart:active{
    background-color: lightgray;
}