This one-man job is a great, and free, first-person physics puzzle game. It will please the fans of Portal, QUBE, Quantum Conundrum and the like, despite being uniquely different in that it's based around using simple DOS commands to hack computers and unlock doors, operate lifts, disable cameras and so on. If you've always felt that hacking in videogames was just holding down a button or playing some abstract minigame, and that proper hacking simulations are too complex, this game strikes the balance you are looking for.

It's not all about hacking either: you'll be required to shoot turrets and robots or sneak past them, stack crates, find ways to smash windows, crawl into vents with night vision goggles, pick locks, turn off gas leaks or use them against enemies, etc. There is plenty to do here.

It's highly replayable too, since each level can be completed a number of ways to achieve a 100% rating and see the true ending.

If anything's wrong with it is that some of the DOS commands aren't very well explained or too specific, requiring some googling, which will direct you to a guide by the developer himself. For instance, cameras require you typing "set off" to shut them down, when "turn off" or "disable" would have been more intuitive.

Small quibbles aside, this is a fine game that any fan of the genre should play.