FlappyBird is more than a game. It's a phenomenon. It's a legend. In some ways it's the new Hello World: one of the first programs someone writes as they start exploring programming.
This guide will walk you through a FlappyBird style game implemented in CircuitPython on the NeoTrellis M4 Express. That's right: a video game on the NeoTrellis. Why not? It has lights and buttons. That means you can write games for it. Furthermore, those lights are in a matrix (albeit a scant 4x8) which means they can be used to display more than a single bit at a time.
Since this board has a SAMD51 at it's core, there's plenty of room to write well structured object-oriented code, so this project will use a few software engineering best practices while we're at it.