They have other options as well. Flappy birds is one of the themes.

They're all just Flappy Bird themes, though.

Flappy Bird isn't even a rewarding game, so it's a weird thing to base a project around. No one I know can score higher than 5 in Flappy Bird.

I don't think you're giving enough credit to Flappy Bird. It's clearly a skill based game, but it's not something you can pick up right away and be good at. It takes at least 30 minutes to an hour to get decent. I remember when I was first playing and I finally broke through and had runs of 30, 40 then 70, all in a row. I felt pretty accomplished.

Now I still play sometimes, almost as a way of relaxing. Once you get the hang of it, it's easy, but you still have to pay attention and you can still get tripped up. I'd say it's a very rewarding game.

Just yesterday I finally beat my friend's score of 171 with 203.

My younger brothers all do a lot better at the game than me (and everyone you know), the top two scores between two of them are 41 and 26.