Thanks so much for your feedback – this gives me so many brilliant and specific things I can look to improve, so thank you! I got a bit lost with walls as I was trying out 'image to Bitsy' and have so many tiles 🙈but do think this needs updating in the game. Also the key, I cheated and just used it as a nice bit of dialogue trigger, but can definitely see the advantage of introducing proper logic here and having you collect it before the doors unlock. I will investigate how to add the full size option. Thank you again!
There is a full screen checkbox on the itch page settings, as well as the dimension settings, and in Bitsy's Settings box (under Tools) there are also full screen and fixed size options (I'd recommend at least 512x512) so you should get it with a bit of fiddling with all of those.