Brake Lights & Blinkers

Added brake lights and turn signals. Cars actually using their turn signals feels unrealistic to me.

A bunch of tuning and the traffic is still not as convenient to navigate as the original version, where every adjacent lane was always going in the opposite direction. I have, however, dramatically improved the enemy spawning to the point where it's actually a bit scary when you trigger a new wave, and enemies that go off the screen are "respawned" almost immediately so they won't stay off screen.

GIF on Imgur