.bar {
    border: 1px solid #666;
    height: 20px;
    width: 100%;
}
    .in
{
    animation: fill 60s linear 1;
    height: 100%;
    background-color: red;
}



@keyframes fill {
    0% {
        width: 0%;
    }

    100% {
        width: 100%;
    }
}