Great idea! Good execution too for such a short time. First i just killed everyone and thought that you really messed up and then i saw that you had a rating system. Great thing to add replayability. You should definitly expand on this.
Unfortunately the rating system isn't working as I ran out of time (so get used to F grades!) however, you indeed guessed correctly that higher ratings would be achieved by killing fewer enemies. Also, time was going to be a factor, but I didn't have time to add a timer... :p
