Holy crap dude this has got some style to it! Expanded this seems like the kind of game Nintendo would like on the Switch (I don't mean that as an insult, like actually try to make money with this ^_^). A few things: If you had an audio prompt on the letter change it would make it easier to know when you need to switch letters.
Also it doesn't matter which letter you press they all do the same thing.
All in all great job!