VScript, introduced in Left 4 Dead 2, is a virtual machine for scripting that acts as an abstract binding layer between the Source engine and external scripts. According to the Alien Swarm SDK, the following scripting languages are, or could be supported in the near future:
Script files are read from
/scripts/vscripts/ inside the game directory.
- Portal 2 (Client/UI only)
Main article Vscript Fundamentals