If you are mourning the loss of Flappy Bird, and the abject lack of clones (okay, I'm being sarcastic, I admit), then mourn no more!
Robert Roth, a Gnome developer, has created a usable clone (in Vala) for the Linux desktop. Along with that, he's written a tutorial for fellow coders (integral with the code as comments). The entire application is less than 150 lines of code!
NOTE: If you try to run the game on ATI/AMD graphics cards with open source drivers, you may get performance issues (sad for me, because I am in that boat). Nvidia and Intel drivers wok just fine.
Here's a video of the original version (without CSS Styling):
Download the official 2buntu app for both Android and Ubuntu Touch.