Fires many small, green projectiles. When they hit the ground, they bounce around a bit and then explode. They can explode early if they hit an enemy, also dealing damage. Damage is distance based.
The tadpole and its upgrades instantly explode when directly impacting a tank.
Firing at a more horizontal angle will cause less spread, thus making it more likely to hit.
The tadpole and its upgrades deal more damage with range.
If an enemy is a good distance away, and you have a clear shot when firing at a horizontal angle, that is the perfect recipe for maximizing your damage.
Close range shots still deal decent damage, and are very likely to hit.