Players have to swing “shlang” (As my little brother likes to call it) a ball attached to an elastic band at enemies to protect their base. After each wave of attack, they can choose an upgrade for the next level!
The ball you swing and the base it’s attached to has some strange properties… they are slightly magnetic, and sometimes suck enemies in, only to send them flying.
It happens quite rarely though. Players also get a helper. A small jet fighter that can be upgraded to shoot at incoming enemies.