Zombie riot is a zombie mod co-op in which you must fight against the zombie hordes, actually, you need to survive. If you want, you can call it a replica of Killing Floor. The only difference between killing floor and this plugin for CS:S is that the zombies don't have special abilities and the weapons are the one you buy (the standard ones, D-Eagle, FA-MAS, Steyr AUG, after their real names). There is also one more thing that they spawn in the terrorist sp (spawn point) which I think, mappers can add it where they want so they might spawn where the map has T sp.
Fortunately, I found some videos on youtube and I wanted to show you how the mod looks:
As you can see in the video, there is a HUD at the bottom center of the screen which shows you the day(wave) that your team is at, the number of zombies left, the name of the day which the owner has set and the number of humans left (your teammates).
I hope you guys will enjoy watching the video and as well, playing this mod.