The style choice is awesome and it's very gentle at the eyes: no big deals to play for long periods of time. Yeah, the game is too hard to play, and personally I would either change the gravity to be stronger or let the pipes be more far apart, or both. Also, future pipes are harder because you cannot know if your current height will be fine to pass them: it's a question of luck. Sound design is cool, it really gives the sensation to be a very fast bird, that is so cool! Flappy Bird is little, so I don't have many more things to say. You can give it a background, a simple background: it does not need to be cluttered, because of your monocolor style choice, but it needs to be clear that it's a background and not an object of interest for the player. My personal best is 3!