Protium

Protium is a side-view horizontal scrolling shooter where the screen scrolls constantly from left to right as you control spacecraft blasting and avoiding aliens over various levels. Earth have been threatened with hyperspace by the aliens and because their base is so far away, an attack isn't plausible. The only solution is to activate the Galactic Shield but this requires large amounts of Protium and there isn't any on Earth. To get some, Protium, a ship laden with it has to be stolen and brought back to Earth to save the planet. The aliens attack in formations and if you touch any or are shot then you lose one of six lives. Icons occasionally appear and when one is touched then you receive a power-up and these are extra fire-power, extra speed, reverse fire, laser, plasma bomb and shield. Half-way through each level, a Mothership appears and must be destroyed to progress through the level.