Nice job. I run a relatively popular Simon Ear Training game for piano/guitar (link on my bio if interested) so always happy to see more musical edutainment games.

Some feedback as a musician: in general, you want to avoid a metronome that maps to distinct pitches (in your case, it sounded like E on the downbeat and A on the others) because it can subtly interfere with new learners as they build a mental connection between notes and pitches.

Note that you need to play the first 2 introductory levels before you have access to the minigames. Sound invaders is the mini-game I focused more on.