* {
    box-sizing: border-box;
}

body {
    margin: 0
}

.full-page {
    height: 100vh;
    border-top: 4px solid silver;
}

canvas {
    background: lightgoldenrodyellow;
    margin: 50px auto;
    display: block;
}

.silver {
    background-color: silver;
    display: none;
}

.skyblue {
    background: skyblue;
}