Level 12 will never be the same twice !
Bullets are limited to the initial level (100) and can be increased by shooting bombs during the game (+50/bomb).
So there are three ways to lose :
No more bullet, no more lives and invaders touch down.
You have 3 lives in level 1 and one more at each new level.
New secret level for Halloween for kids! (access with H)
New secret level Virus for 2021 (very difficult - access with V)