A simple C++ shooter game

This is my first attempt at Entity Component Systems (everyone's gotta have one, right?). Originally I was going to try to write a small reusable library, but I decided that I would learn better if I tried to actually implement a game.

The main mechanic is that the player moves in a circle around the enemy spawning point, and bullets are directed towards the center of the circle. However, you can't just spray n' pray - bullets are valuable and shouldn't be wasted.

The actual executable can be downloaded here: https://www.dropbox.com/s/e4mgv1qfvqpubb9/CircleVsSquares.zip