   defend: (missile, destroy_area) -> 0
 
 class MapUnit2DForBrick extends MapUnit2D
+  weight: (tank) ->
+    160 / tank.power
   current_frames: () -> [{x: 0, y: 240}]
   defend: (missile, destroy_area) ->
     # cut self into pieces

        @inputs[key].push("keydown")

class EnemyAICommander extends Commander
  next: ->
    # attack home
    # attack user tank
    @battle_field_object

class MissileCommander extends Commander
  next: -> @move("start")

class MapUnit2DForUserTank extends MapUnit2DForTank
  defend: (missile, destroy_area) ->
    return 0 if missile.parent is @model
    @max_depend_point - 1

class MapUnit2DForEnemyTank extends MapUnit2DForTank
  defend: (missile, destroy_area) ->
