Remove CBaseEntity::VPhysicsShadowCollision (S1 legacy code) Delete PhysicsGameSystemS1 and other unused crap Get rid of legacy gamevcollisionevent_t, cleans up calls to CBaseEntity::VPhysicsCollision Move C# collision interop from CBaseEntity::VPhysicsCollision to CPhysicsGameSystem::DispatchCallbacks, call C# once per collision instead of once per entity in that collision. Give ourselves additional data to expose onto the game API.