This app was mentioned in 4 comments, with an average of 1.00 upvote
This is probably one of the smoothest twists on a flappy bird style physics game I've seen. It feels great to play and I am very impressed. There are two things I would pick on that are not essential to the game play but are to the user experience.
The fonts are not consistent. This is something that people will immediately pick up on and screams neglect from the developer. Consistency is a major factor in user experience and should not be taken lightly.
The colors work pretty well in game but not sure about some of them on the UI. Consider using the material design pallets to revise this and see if it improves it at all? THIS is what I use. And HERE is a game I just released that uses it if you want an example.
Not multiplayer but you can text your mate a screenshot of your high score to piss him off: HERE