Since every Axe coder and their grandmothers were making Flappy Bird clones, I decided I should get mine out of the way. Naturally, I had to try to make a very optimized version. So I present to you a complete implementation of Flappy Bird, weighing in at a fairly petite 647 bytes! (when compiled for Ion)
Partially because I'm lazy, and partially because I knew it was already a good, working implementation, I started with a compact Flappy Bird implementation that Matrefeytontias was kind enough to let me
steal borrow. That weighed in at 898 bytes and didn't have scoring, so I'm pretty happy with myself for managing to cut out 250 bytes while also adding scoring. That said, I think Matrefeytontias created graphics and coded his whole version from scratch in just over half an hour, which is very impressive. My adjustments took about an hour and a half.
Source and compiled programs attached.