Hmm, my guess is you're trying to use the box's borders as lines (they don't count, only the lines you draw count). Let me know if that's not the issue. Also, I'll think about ways to make this more clear!

You could automatically "zoom out" what they draw if they get too close to the border.

Alternatively, you could automatically "close" figures after they have at least three points, and give a hint of a handle that allows dragging a new point out of the middle of an existing side.

Ah okay -- the second one had a map with the same shape as the border, which I think made me mentally lump the map's border with the box's borders and invalidate the claim that it's looking at the box's borders as part of the map. I also assumed you wouldn't possibly expect someone to have to explicitly draw all their borders when they can piggyback off the box.

Entirely my mistake because I was kind of ignoring everything you said lol