style.css

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

body {
    text-align: center;
    font-family: sans-serif;
    color: cadetblue;
    background-color: black;
}

main {
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
}

canvas {
    outline: 1px solid whitesmoke;
    /* background-color: #00ff21; */
    max-width: 610px;
    width: 100vw;
    height: calc(100vh - 20px);
}

#character {
    display: none;
}

#gameover,
#restart,
#start {
    display: none;
    position: absolute;
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);
    background-color: antiquewhite;
    padding: 30px;
    border-radius: 4px;
}

.restart-btn {
    padding: 5px 14px;
    color: cadetblue;
    font-size: large;
}

#gameover.activate,
#restart.activate,
#start.activate {
    display: flex;
    flex-direction: column;
    gap: 20px;
    align-items: center;
}

@media (width < 768px) {
    canvas {
        outline: none;
    }
}