Drone

=Description=
 * Drone is an unique tower capable of damaging infinite-armoured enemies that most of the others can't hurt. It sends a group of small, flying drones to attack a single enemy for 15 seconds, dealing great constant damage. Each rank up adds another drone to the group, but this does not increase the total fire rate of the drone group. It's effective against single troublesome enemies, but not the crowd or weaker ones.

=Gameplay Notes=
 * A single enemy cannot be attacked by multiple drone groups at the same time. If the enemy dies before the 15-second lifetime of the drone group is up, the drone group is destroyed.
 * A new drone group can be spawned every 5 seconds. This means that there can be 3 drone groups out at the same time at maximum.
 * The shots from a drone group ignore armor. This makes it a great tower against any armored enemy, the only tower that can hurt Bobble Heads, and the only tower unaffected by Hoverers' armor (though AR-Mines can hurt Hoverers and Rupture Mines can hurt both Bobble Heads and Hoverers).
 * Drones are also a reliable way of intercepting single fast enemies that slip through your player frontline and break away from the main mob, or of dealing with fast enemies in general, since they always apply damage to targets for 15 seconds, regardless how quickly the targets passed through the tower's range.
 * If Hydra Hunter is active and you want to fine-tune the total damage of a drone group to the hitpoints of the imminent enemies, assuming no damage from other sources is applied to them, you simply need to subtract 2250 from the total damage; this is the amount of health enemies will regenerate during those 15 seconds the drone swarm lasts.