* {
    box-sizing: border-box;
}

html, body {
    margin: 0;
    padding: 0;
    min-height: 100%;
}

.main {
    width: 100%;
    height: 100%;
    display: flex;
    justify-content: center;
    flex-direction: column;
    align-items: center;
}

.main > * {
    margin: 1em auto;
    display: block;
}

footer {
    width: 100%;
    border-top: 1px solid lightgrey;
    padding: 1rem;
    background: rgba(0,0,0,0.1);
    margin-bottom: 0 !important;
}
footer p {
    margin-bottom: 0;
}

textarea {
    display: block;
    width: 80vw;
    height: 30vh;
    min-height: 20vh;
}

canvas {
    border: 1px solid;
    display: block;

    margin: 1em auto;
    width: 90vw;
    height: 70vh;
    max-width: 600px;
    max-height: 600px;
}