Flappy Bird was created and developed by Dong Nguyen in the span of two days and originally released on 24th of May 2013, it gained remarkable success early this year. However, it was soon taken down by its creator for being too addictive and that he "cannot take this anymore." Don't worry though, just like Angry Birds, there are many free alternatives available online!
The closest that comes to the original is perhaps these HTML5 and Flash variations of it. The objective is the same: to direct a flying bird, which moves continuously to the right, between each oncoming set of pipes without colliding with them, which otherwise ends the game.
You can also play Flappy Bird with many other players online with this Massively Multiplayer Online (MMO) version of the game. You can create your own party to play with your friends, and it also allows you to choose from 3 different visual themes, on FlapMMO.
While there are countless other clones, remakes and parodies of this game, the gameplay is more or less the same so they are not listed here. There are a couple of spinoffs that got my attention which are worth mentioning though. The first one brings a new twist to the already notoriously difficult game by making it like a typing tutor. Not only you need to watch out for the obstacles but also type the words correctly.
Finally, there is this brand new online game. Unlike most spin-offs, however, Flappy Space Program is more than just a reskinned clone of the game. All it shares with the original is a similar name, a simplistic concept, and frustratingly difficult, yet rewarding gameplay experience. The goal of the game is simple: repeatedly tap (or click your mouse) to launch a mechanical space bird into orbit. Once the bird is successfully orbiting the planet, you'll be given another bird ship which you have to launch. There's no winning, only launching more bird ships into orbit with the hope of achieving a new high score.