ISP tweaks L4D2 to give the player a challenging, well balanced, immersive survival horror game with a tactical flavour, bot commands, a new sneak system to get through neverending hordes and a few options to customize difficulty and gameplay. ISP works with any coop campaign and map, original or custom. It should fully work on survival maps too, but its not going to be easy. It is highly reccomended to play ISP without crosshair (press 6 to disable it).