initial implementation of bat's update function (todo: make bat oscillate up and down while it also moves in x axis, and also code bat's collisions with player, adding to falling list if necessary, or being filtered by player's attack)

fcore/constants.sml

@@ -30,6 +30,7 @@ struct
   val enemySize = 35
   val enemySizeReal: Real32.real = 35.0
   val moveEnemyBy = 3
+  val batRestLimit = 155
 
   val moveProjectileBy = 11
 end