The mechanics are simple but it works perfectly! The way in which the elements of each character are handled (such as the life bars) are excellent with the type of game. The background music is a great element to keep the player alert. Also, great way to implement the "Stronger togheter" in the game, I love the idea of how you have to stay with the survivor for a while instead of being immediate. It certainly adds tension to the game.
Great job!!!!