pencil-js/pencil.js

body, html {
    height: 100vh;
}

body {
    margin: 0;
    display: flex;
    flex-direction: column;
}

header {
    padding: 1em;
}

#loader {
    display: inline-block;
    height: 1em;
    width: 1em;
    border: 4px solid;
    border-color: red green blue yellow;
    vertical-align: middle;
    border-radius: 50%;
    animation: rotate infinite linear 1s;
}
#loader.hidden {
    visibility: hidden;
    animation: none;
}
@keyframes rotate {
    to {
        transform: rotate(360deg);
    }
}

main {
    display: flex;
    flex: 1 0 auto;
}

main canvas {
    display: block;
    flex: 1 0 50%;
}

footer {
    padding: 1em;
    height: 100px;
}