When we buy walls and towers, as well as other base defense enhancement item, it clearly shows the base defense is boosted at a certain level. However, when turret and artillery are down, the wall and tower's defence are inactive. In other words,  it seems wall and tower only has effect when there are military units present in the base. This is not correct because wall and tower has their instinct defense value, this should not be affected by other factors. If wall and tower's defense points are so easily neutralized, why we spend so many diamonds buy them? You are cheating the player. Please correct this bug and let wall/tower's defense active in any case.