Oh I see. Yes, there are some quality of life improvments that would've been nice like a map, an inventory, an in-game language selection options and audio controls. But I think the gameplay is top notch just like art (music and visuals). Usually when I read "quality" I think of gameplay and art.
FYI, I did got the "jtiles" bug, but after reloading the webpage I could keep playing. It is a good thing you could replicate it and fix it. It was just a softblock, but visually was ugly-looking. I totally can understand how a user might be thrown off after seeing it. However, I think it's a lesser bug compared to the ones you can find in some real GBA games. For instance, in the PAL version of "Legend of Zelda: The Minish Cup" you have unavoidable bug that prevents you from getting the last bomb upgrade. It is explained in this video:
(The bug I mention appears at around 11:33) If nintendo got away with it, you should also get et away with it ;).
Two last things:
1. I think it would've been nice if you could replay the boss, but that's not here nor there.
2. There is a bit of a exploit, since you can reload the webpage and make gems respawn. This exploit can be used for 99 gems item. I don't consider it a bug because maybe that was intended, but it is an exploit for speedruns and such.