Restraint is a top-down action shooter that is much more complex than it appears with 20 levels, teleporters, bad guys, and more.

We spent some time playing it but were hampered by the forced use of WASD, which we never really got the hang of.

Of course, then there's the game creators rather long description (and wait until you see the readme.txt):

Anteros, Earth's first fully functioning colony on Mars, has been infected by an alien entity codenamed "Echidna," which was banished from the galaxy after two previous failed invasions. Echidna intends to hitch a ride back to earth using the Anteros radio waves. Humanity's only hope: a suicide mission to mars, starring certified lunatics Ollie and Jayla -- the only two humans ever to face Echidna and live.

Restraint is a spiritual successor to Shudder, and the Jayla series to an extent. Choose between two disturbed protagonists: Ollie, who plows through every monster in his path, and Jayla, who prefers the stealthy approach. Fight your way through 20 levels of blood, mayhem, and teleporters!