So this here is a lesson in text readability. I'm struggling to play the game, not because I can't remember the pattern (when it comes to memory games, I'm actually quite good, especially when music is attached), but half the time I can't read the letter I'm supposed to press before it vanishes. You need to find the middle ground between text that matches the style of your game, and text that people can read at a glance. This would be even worse for people with visual impairments or dyslexia.
As far as gameplay goes, I've actually played nearly this exact minigame in Guild Wars 2: End of Dragons. Go figure :P It's not a terrible concept or anything, but it's a bit like making an infinite runner. It's great for learning purposes, but as a game, it's largely unmemorable.
Ok, so this is a largely negative review, and sorry, normally I prefer to give a mix of positive and negative feedback. That said, keep trying! You'll get better as time goes on. The first time I tried adding my own music to a game, the comment I received from the jam judge was "OMG MY EARS ARE BLEEDING". Trust me, you can't do worse than that... So keep going, and take the technical skills you learned from making this game and combine it with some design lessons to make something fantastic. Whatever you make next, I'll be there to play it.