       @jumpMaxDuration = 500
       @jumpVelocityFactor = 1 / 4
 
+      @airFrictionRatio = 1 / 20
       @runAcceleration = 300
 
       @maxVelocity =


      if @isInMidAir()
        # No force, just air friction.
        @acceleration.x = @runAcceleration / -20 * direction
        return

      else if isStill or landed()

      @animations = @sprite.animations
      @_initAnimations()

      @cursors = game.input.keyboard.createCursorKeys()
      @direction = Direction.Right

      game.physics.arcade.enable @sprite
      @gravity = game.physics.arcade.gravity
      @_initPhysics()

      @debugging = on
      @debugTextItems = {}
