Seriously? Flappy bird is original? Its mechanics and graphics were both shamelessly lifted from Super Mario Bros. which is almost 30 years old. It's about as original as pong
The finished project was an "original app" for all intents and purposes. The mario elements aren't trying to be passed off as their own and the mechanics are loosely based, which most video games are. In that line of thinking most 3D games are blatant imitations of Super Mario 64/OoT and all FPS are copying Goldeneye. There's a difference between basing a style on something while paying obvious homage to a classic video game and substituting a few sprites and re-releasing it to jump in on the cash grab.