Implement weapon 2 level 2

Details regarding weapon 2:
- level1 :
if tower is located on position with (x, y) greater than (30,30), this
weapon will send the enemy back by 30 pixels
if tower is located on position with (x,y) less than equal to (30,30),
this weapon will send the enemy back to (0,0)

-level2:
whatever the position is, this weapon will send the enemy back to (0,0)

Note that this weapon does not cause any damage to the alien's health.
Let me know what you guys think. :)