Instead of shooting two portals, one entrance and one exit like Portal, p.i.g. has you shoot one block that creates a tunnel to another side. You'll do this by moving around the screen with the 'a' and 'd' keys, while 'w' will let you jump and moving the mouse around will target the portal... er, tunneling gun.
It might sound like a Portal clone when you read the description, but when you actually play it you'll see it has its own logic entirely. That said, p.i.g. doesn't ignore Portal's existence -- it takes the gravity mechanic, that is, "an object in motion stays in motion," and runs with it. You'll have to use the increasing momentum to get to new areas at certain parts of the game, and it can get very tricky, very fast.
You'll have to do things upside down and right side up, and you'll eventually get to a point were you'll need to use quick clicks and fast action to get through the sections. There's not a whole lot of lateral thinking, it's mostly spatial puzzles that have very clear strategies, but you'll still break your brain a couple times throughout.As far as the story and reasoning is concerned, it's very reminiscent of Portal, with a sentient, wisecracking A.I. goading you along and making you feel inadequate throughout.
It's a short game, but it's also pretty tough. It doesn't quite perfect the balance of a good puzzle game where you come up with the solution at the exact moment you plan on giving up, but it's a great start and a sure-fire good way to spend a few moments of your time.
Play it here.