In which case, it is one hell of an extensive mod. With, might I add, is getting another update!
This update: Zombies, four new ones. Each zombie is original and has powerful strengths and weaknesses. The first one is the Sprinter. It bum rushes you at a speed faster than you can travel for heavy damage, but has health low enough that they can be killed in one shotgun shot. In swarms, they are quite a threat.
The second zombie is the spewer. With quick speed and highly toxic bullets, it can destroy walls and quickly kill you if you let it get too close. At close range they are extremely dangerous.
The third zombie is the ghost. The ghost can pass through walls and barriers at a high speed and can avoid bullets. To make up for this advantage, they are weak. However, stronger shots are much more likely to miss, the most efficient way to kill them is with timed, measured, pistol shots, requiring you to consider whether to kill them or get swarmed by zombies.
The final zombie is the giant, the ingame equivalent of a tank. It can take multiple shotgun clips to its body before dying, it instantly destroy walls, and contact with it is near sure death.
I have built a room where you can see all these infected in action and their abilities. I put each one in a corner so that until you move towards them to engage them they will not engage you. Should you for any reason need to return to the room's middle, press R.
EDIT: I just realized not everyone has the full version of game maker

. Therefore, I am posting an executable.