In Strike Suit Zero, the protagonist has to save Earth which is in war with its space colonies. Unfortunately they found a mighty alien artifact which makes things a bit intense. Regarding gameplay, this is a standard shooter: the player flies through the 13 missions and kills all enemies which are usually much weaker than the player's ship and are dangerous because of their numbers and occasional time pressure. The levels are linear and have varied objectives like destroying targets or escorting.
The game features four ships which are unlocked during the campaign and differ in optics and weapon slots: before each mission, the player can change the weapon loadout. The only major difference is the Strike Suit ship because it can transform into a mech which can target many enemies at once. However, this mode is only available for a short time when the energy bar is filled by killing enough enemies. The ships can be upgraded when solving secondary missions. The missions have temporary checkpoints (quitting the game erases them) which give full health and weaponry after death, but also minus points for the online high score list.