at 1 1 wood . at 1 1 wood . at 1 1 wood . at 1 1 wood . at 1 1 wood

#update: {
  at X Y wood . + X 1 X' . + Y 1 Y' . + X'' 1 X . + Y'' 1 Y = at X' Y' fire . at X' Y'' fire . at X'' Y' fire . at X'' Y'' fire
  at X Y fire . + X 1 X' = at' X' Y fire
  at X Y fire . + Y 1 Y' = at' X Y' fire
  () = #process
}

#process: {
  at' X Y I = at X Y I
  () = ()
}