Protector

Aliens are hell bent on destroying your civilization's tower. They are sending their minions to destroy your tower. All you have initially in each level is unlimited arrows, using which you can destroy the minions. The minions, upon destruction give you some coins, using which you can you may upgrade your defenses. Remember, the level is not over until you destroy that level's boss, which does not come out until necessary. So you have to lure it out and destroy it.