PRESS GREEN FLAG TWICE!!! Press [SPACE] to start the game. Press [SPACE] to flap.
This is INSANELY laggy on low-end devices, so don't even THINK about playing this on something like a Chromebook or an old phone. It even lagged a bit on my PC, but running the project in Turbowarp fixed it. Just don't trust Turbowarp to make it 60FPS and actually playable on something that can't handle two Chrome tabs.