I’ve worked for one of the developers of Piou-Piou. The game was released in 2010, didn’t meet much success at the time, and like a handful of games from the same group was discontinued. The recent video was published after heated discussion on how Flappy Bird ripped them off (during which I wrote to them it was unlikely -- not sure they agree, to this day).

They also made a handful of games that were successful, several that went through very public controversy about being copied from someone else; several that have been stolen quite blatantly (with the original developers nicknames in the function calls). That cycle hasn't stopped there: reverse-engineered a game for cheap, etc. I won’t give details because I don’t like talking to lawyers, but all was as transparent as those things can be.

I’ll say here what I said then: if someone steals from you, there's always a slight difference that could be an improvement, take that; otherwise, every game has its own history. Learn and let it be.

If that's true they also either hacked YouTube or created a time machine so they could go back to 2010 and post this:

https://www.youtube.com/watch?v=MpxmqejpR0Q

I've lost count of the number of different titles that Flappy Bird is supposedly a rip-off of.