If you're enjoying the Project 11 game, one thing that you may find is that we're not cleaning up the emitterNodes that create the explosions. It is a simple game that's not particularly demanding on the graphics. However, it's nice to clean up nodes after they are done, like the ball, so you might want to add a dispatch queue with wait time and execute code to remove the emitterNode (fireParticles) from its parent.

Cheers