*{
    margin: 0;
    padding: 0;
}
body{
    text-align: center;
}
#game{
    width: 500px;
    height: 500px;
    margin: auto;
    border: 1px solid black;
}
#btn{
    font-size: 2rem;
    cursor: pointer;
    padding: 0.5rem 2rem;
    border: 3px solid black;
    border-radius: 10px;
    margin: 1rem auto;
    background-color: lightgreen;
}
#btn:active{
    background-color: red;
}
.slider{
    visibility: hidden;
    height: 20px;
    width: 200px;
    background-color: red;
    position: relative;
}
#slider1{
    visibility: visible;
}
.animate{
    animation: slide 4s infinite linear;
}
@keyframes slide {
    0%{
        left: 0px;
    }
    50%{
        left: 300px;
    }
    100%{
        left: 0px;
    }
    
}