decided not to add realistic physics simulation

I was considering using Nape as a physics engine to make interactions more realistic.

This video shows what happened when I set it up wrong.

In the end, once I had configured it correctly, I decided against using the physics engine because it's a bit too realistic: since the player boat has about the same mass but a higher speed than the other boats (to make the game fun!), it also gets significantly more momentum, causing it to whack other boats around in a way that just looks silly. For now, SuperBoats 2 will continue using the in-code momentum simulation.