Lovely minimalist graphics, and I love the concept of a button-mashing contest! I didn't have anyone to play it with me so I just decided to use two rounds to see which hand of mine is better at button mashing. (Left = 195, Right= 203. Pretty even, actually!)
Weirdly enough, this game reminds me of the final boss of a DS game from my childhood. You had to mash Y repeatedly to survive the boss' final phase - I actually played the music from it over the game since you didn't have any.
Overall, great game! Probably not one to play too often in a row due to how fast it tires out your hands, though, haha.