What to do now is very similar what you did in the previous chapter. Instead of stacking pictures horizontally, you are going to "stack" them vertically.

Copy and pasting and changing horizontally in vertically will bring this chapters goal within reach. And there is nothing wrong with that.

But if you want to challenge yourself, you could also think of using the tools already present. By cleverly combining turns and above one can get beside.

Either way, once you created beside, make sure to test it out. And say goodbye to src/canvas/mod.rs, you won't need to touch it again. All the primitive operations are in place.