To start off it could really use some music to keep people entertained while they are playing, also a timer for levels and score system so it challenges people to get better scores. a back to menu button if a timer is made to get a better score and redo levels that have been done. maybe an enemy that walks a certain pattern so you have to avoid causing it to be more challenging w/o these things its simple and doesnt require skill. hope these ideas help you, good luck :)