Left
4 Dead 2’s developers have released the Extended Mutation System, an
improved scripting system that allows for much greater modification and
customisation, giving script authors the opportunity “to go past
modifying existing scripts and write custom script logic, spawn and
control entities, and much much more.”
To
give modders an example of the sort of thing that’s possible with this
system, a new survival mode known as Holdout is included with the EMS.
It’s a four-player co-op game mode where the team must defend their
stronghold against waves of infected while trying to provide power to a
spotlight that will summon a rescue helicopter. It functions as both a
game mode and an introduction to what the EMS is capable of.
To
guide modders through the new scripting process and help them get a
handle on these tools, Valve have (very helpfully) created have created a wiki and a starter’s guide. The wiki also explains a little about the Squirrel
Scripting Language that lies behind the EMS and it covers everything
from placing entities to spawning objects to changing global game
states. Anyone who has coded in Lua or C will find Squirrel familiar.
You can find out more about the update by visiting the L4D2 blog right here.