anchor.diff:                      Log.trace (scstring exn)
                       World.cleanUp world
                       Constants.Engine.FailureExitCode
  -#if MULTITHREADING
  +#if MULTITHREAD
               // stops background threads
               Environment.Exit result
   #endif
  
positive.code:                                         let world = World.actualizeSimulants world
                                          match World.getLiveness world with
                                          | Running ->
  #if MULTITHREADED
                                              // attempt to finish renderer thread
                                              let world =
                                                  match rendererThreadOpt with
  
negative.code: open System
  open System.Collections.Generic
  open System.IO
  #if MULTITHREAD
  open System.Threading.Tasks
  #endif
  open SDL2
  