body {
    margin: 0;
    height: 100vh;
    display: flex;
    flex-direction: row;
    align-items: stretch;
    overflow-y: hidden;
}

#left-pane, #right-pane {
    max-width: 25vw;
}

#middle-pane {
    flex-grow: 1;
}

#main-canvas {
    width: 100%;
    height: 100vh;
}