At first i thought it didn't work, when I couldn't click anything in menus. I'm glad that I tried the keyboard, because this was very fun.
Nice, clean and simple graphics matches the simple but rewarding gameplay.
I'm guessing that the music is supposed to change when rage mode ends. That sometimes didn't seem to work properly for me, fooling me that it had ended early. But that's a small thing in a game that otherwise feels very polished.