Thank you for playing!
Yes, it seems you weren't the only one to run into that problem. I may add an undo button to try and help with it, though it will take some time coding. I've added in a re-do button after the giraffe too, as I forgot to add it.
As Mosi / Bitsy doesn't really give you button presses, I don't think there's a way for me to code it where you could work from the inside-out as you need a wall to hit. I don't think there's another way to do it, so I will try and make it a bit easier to fix mistakes at least.