itch.io

Believe me, this game deserves that and much more. Lots of respect to everyone working on it!
Yeah, I suspected you weren't using Z to continue because of that. Don't worry about it, it was a mostly a personal pet peeve, and I planned to play it with a controller later anyway.
Black bars will be a great addition,  I found myself fighting against those scaling issues for my game too, and in the end solved it by letting the player choose even resolutions and then stretching that with antialiasing for the full screen mode (so on a 768 monitor the game will actually run at 720p, getting a little stretched) of course some minor blur will be involved, but I find it barely noticeable. 
Really nice effect there on the guitar, it totally has some synthy and retro sound that fits perfectly with the game while still sounding like the real thing.