index.css

@import url('https://fonts.googleapis.com/css2?family=Roboto:ital,wght@0,100;0,300;0,400;0,500;0,700;0,900;1,100;1,300;1,400;1,500;1,700;1,900&display=swap');

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html,
body {
    font-family: 'Roboto', sans-serif;
    user-select: none;
    color: white;
    height: 100%;
    font-weight: 900;
    font-size: 2rem;
    overflow: hidden;
    display: flex;
    justify-content: center;
    flex-direction: column;
    align-items: center;
    background-color: black;
}

canvas {
    display: block;
    background-color: black;
    border: rgb(17, 17, 17) solid 5px;
    border-radius: 2rem;
}

#overlay {
    position: absolute;
    display: flex;
    flex-direction: column;
    justify-content: center;
    transform: translateY(-250%);
    transition: transform 500ms;
}

#replay {
    /*display: none;*/
    opacity: 0;
    border: none;
    border-radius: 16px;
    color: white;
    font-weight: 700;
    font-size: 0.5rem;
    line-height: 0;
    padding: 1.5em 1em 1.5em 1em;
    background-color: hsl(135, 100%, 20%);

    transition: background-color 100ms opacity 500ms;

    &:hover {
        background-color: hsl(135, 100%, 30%);
    }
}

#overlay.show {
    transform: translateY(0);

    #replay {
        opacity: 1;
    }
}