So far, I don't think I've had any problems with actual words not registering. Was very surprised to see that "Lagomorph" (Hell, my browser doesn't even recognize it as a word), "Incest", and "Adultery" were all valid (I used them for the bonuses, shush). Honestly a really fun game though, I like how you can collect letters as you progress and combine them into more valuable ones. Not some linear garbage where you hop level to level endlessly with no sense of accomplishment or reward.
-Disclaimer: I haven't yet beat the game-
Unfortunately, this game doesn't really seem to work in a browser. There's too much of an input delay. I'm not sure how other rhythm games such as FFR pull it off, maybe it's because there's a lot less visuals to be processed, but there are definitely some issues.
However, I think this could help:
*Before the opening, it'd be nice to have a moment where the player can tap to the beat of the drum to calibrate offset, and then follow up with the small demo. *
That aside, the game is gorgeous. The bird is adorable and the animation is awesome. In its current state, I'd give the game a 3.5/5.