A great item of polish that could be added to your game is a particle system. Particle systems can be designed right in SpriteBuilder with the fully featured particle system editor. If you are unsure of what a particle system is, then the best way to learn is by having a look.
In your Flappy Bird project, create a new file. Select Particles and name it
You should see a new file open up with what looks like a flame in the center of the screen:
This is a particle system. Particle systems allow the spawning of many small ...