html, body, #page-container {
    width: 100%;
    height: 100%;
    margin: 0;
}
#page-container {
    display: flex;
    flex-direction: column;
}
#center-container {
    display: flex;
    flex-direction: row;
    flex-grow: 1;
}

#canvas-container {
    flex-grow: 1;
}
#mainCanvas {
    position: absolute;
}