With regards to your questions:
Enemies will circle in a fixed path around the player. They will only attack the player once five enemies of a particular colour are circling the player. The idea is to clear the enemies before they reach a critical mass, managing the crowd to ensure that enemies never rush you. (also, the enemies are never meant to change colour).
I'm very sorry you weren't able to play the game. It was our first major design project, and that added with the time limit made developing additional features difficult. I hope you enjoy it nonetheless.