Enemy Missile Event

Enemy missiles travel down the screen quite quickly, when they are spawned by an Enemy we pass the enemies direction of travel to the missile and then make the missile veer either left or right accordingly, so if the enemy was going left when they fired the missile then the missile will also veer left.

EVENT SPRITETYPE3
 ;======= ENEMY MISSILES ============
 ;======================================
 ; VARIABLES
 ; =======================================================
 ; DIRECTION - DIRECTION OF ENEMY TRAVEL WHEN RELEASED
 ; SETTINGA - availabe for use in your game
 ; SETTINGB - availabe for use in your game
 ; AIRBORNE - availabe for use in your game
 ; JUMPSPEED - availabe for use in your game
 ; ========================================================
 
 
 SPRITEINK 71 ; bright white
 SPRITEDOWN ; go down fast (3 times
 SPRITEDOWN
 SPRITEDOWN
 IF DIRECTION = 0 ; was alien going down when fired?
 ELSE ; if so, do nothing
  IF DIRECTION < 8 ; was alien going right?
  SPRITERIGHT ; make missile veer right
  ELSE
  IF DIRECTION = 8 ; was alien going straight up?
  ELSE ; do nothing
  SPRITELEFT ; alien was going left, veer missile left
  ENDIF
  ENDIF
 ENDIF
 
 
 IF COLLISION PLAYER ; has missile collided with player?
  IF X > M ; is missile to the right of player?
  SUBTRACT M FROM X ; subtract M to find out how far to the right
  IF RND <= 10 ; its a hit!
  OTHER ; switch to the player
  LET DIRECTION = 99 ; trigger the player explosion
  ENDSPRITE ; switch back to this event
  LET DIRECTION = 99 ; explode the missile
  ENDIF
  ADD M TO X
  ELSE ; not to the right
  IF X < M ; is missile to the left?
  SUBTRACT X FROM M ; yes, how far to left?
  IF M <= 8 ; its a hit!
  OTHER ;switch to the player
  LET DIRECTION = 99 ; trigger the player explosion
  ENDSPRITE ; switch back to this event
  LET DIRECTION = 99 ; explode the missile
  ENDIF
  ADD X TO M ; reset M
  ELSE ; must have been a direct hit
  OTHER ; switch to the player
  LET DIRECTION = 99 ; trigger the player explosion
  ENDSPRITE ; switch back to this event
  ENDIF
  ENDIF
 ENDIF
 
 IF DIRECTION = 99 ; Explosion requested
  LET TYPE = 6 ; switch to the explosion type
  LET IMAGE = 4 ; and explosion image
  LET FRAME = 0 ; and the first frame
  LET DIRECTION = 2 ; and tell the explosion its an enemy missile
 ENDIF
 
 IF Y >= 188 ; has missile reached bottom of the screen
  REMOVE ; remove it
  SUBTRACT 1 FROM S ; decrement the sprite counter
 ENDIF