Suggestions:
1) Syntax highlight
2) Better docs (i can help if you want)
3) Img rotation
4) Update auto-upgrade.
5) Keep code undo after save (after save undo history is lost. Probably not your fault, but you can think about this)
6) Better level editor
Bugs:
1) VERY OFTEN when i draw sprite it erases everything, so only last 0.03 second of drawing are kept. Fixes by randomily moving mouse around ...or by opening GIMP and then "upload image " lol
2) Sometimes when pressing "enter" coding screen goes down, and new line becomes top line so you need to scroll up. (uh. minor bug. annoying.)
3) I think there are no more bugs? 2 bugs? perfect engine lol