If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
A platoon of Universal Patrol Troopers (UPT) get sent to the planet Mars on intel that a group of child slaves will be traded there. The UPT infiltrate the slavers fortress and rescue the orphans, but only trooper Blak Sampson makes it out alive. While he waits in the barren deserts of Mars for his rescue ship, he defends the orphans from the slavers swarms of rabid alien grubs.
WSAD/Arrow keys: Movement.
Mouse: Aim and Shoot.
1 - 6: Swap weapon.