I agree! This game was so cute and fun! I really enjoyed it, even though it's super simple in design. The effort it takes to achieve all endings makes it very replayable! Honestly, I definitely recommend it, whether you're looking for a quick play or going the completionist route. Simple gameplay, fantastic art, very intriguing characters and story! A good game for sure!
Since it was a short project, I expect you won't come back to it. If you ever decide to, though, I agree with Matt10y that a few simple additions would make it more enjoyable; number 1 being a way to track your endings.
1) Tracking Endings - An additional space to view which endings have been found. This could be as simple as a list of the letters and a way to mark them off as they are found, but the best/more complex option would be more along the lines of what Matt10y mentioned. I would love to be able to replay just the ending from that page, too, since some of the endings are very similar, with just a few dialogue changes. Not sure how difficult that is to code, though, so I don't wanna press the complexity too much.
2) Menu/Homescreen - being able to start the game, see endings you've collected, and view the How To Play instructions. Pretty simple in theory, but would add a layer of quality to it.
3) Skip the instructions - considering how many times you have to replay, a skip button or (even better) a how-to on the main menu seperate from the play option would ease some of the tediousness when looking for those few elusive endings. Not a huge deal, since the instructions are short, sweet, and cute, but I think it would really help up the game to a more 'professional' level.