FOOTSTEP_SFX = [
  # Start
  ['step_wood',
   'step_carpet'],
  # Blue
  ['step_gravel',
   'step_wood'],
  # Blue Interior
  ['step_tile',
   'step_wood'],
  # Green
  ['step_grass',
   'step_wood',
   'step_gravel'],
  # Green Interior
  ['step_grass',
   'step_tile'],
  # Red
  [],
  # Red Interior
  [],
  # Tower
  [],
  # Tower Start
  [],
  # Blank
  [],
  # Blue Factory Interior
  ['step_metal'],
]