What Portal did for portals, what Braid will do for time manipulation, Polarity does for magnetism. A free, downloadable, totally awesome puzzle-platformer, Polarity is all about using different types of magnetism to make it through the game.
The player is equipped with a dual-magnetism suit: at the press of a button, the player can turn blue and become attracted to orange items while repelling blue ones, or turn orange and have the opposite happen. Basically, you've gotta jump and magnetize your way through four levels full of dangerous platforming and wonderfully clever puzzles.
If it sounds a little weird, it's because I'm awful at writing description: just download the game and enjoy it. It's short, it's fun, and you'll never look at magnetism the same way again.
Granted, I dunno how you looked at magnetism before, but...well, just download it. Or, hit the jump for a further explanation of the game mechanics.
So, as I said before the jump, your character's suit has two settings: blue, and orange. When you turn your suit blue, you attract to orange objects and pieces of the scenery, but you repel from blue objects and scenery. This means that, while blue, you can walk up orange walls but use your similar polarity to literally float over blue structures. And vice-versa when you're wearing the orange suit.
So, imagine there's an electrified blue stretch of floor, far too wide to jump across. Rather than trying to make a leap you could not possibly land, you're meant to switch to your blue suit and simply repel yourself from the blue, electrified floor as you float across the screen.
Or, let's say you're below a hollow compartment with no doors or way in, just a big button and a blue ball. Since you need to hit the switch on your own, but you can't actually get to the switch, you just need to either turn orange and attract the ball to you as you slowly move in the direction of the switch above you, or you can turn blue and sort of push the ball toward the switch using the opposing magnetism.
Is anything I'm saying making any sense? Just download the game and try it out, you'll get a grip on the mechanics almost immediately. Once you get the ability to increase the intensity of your suit's magnetism, you can start launching yourself into the air off similarly-colored magnets.
It's pretty awesome.
Essentially, though, as boring as "a magnet-based platformer" might sound, Polarity is really quite neat. Games like Polarity, which basically exist to explore and simulate the logistics of a single mechanic, can be really goddamned fun. These sorts of games are mainly about asking, "what if we could do this" in regards to their mechanic; if we could wear magnetized suits, what movement possibilities would arise from that? If we could put portals in solid objects, or slow down time with the press of a button, how would that affect our abilities, and what puzzles could arise from that?
As a result of this design philosophy, games like Portal or Polarity are much more interesting. They're otherwise very accessible, save for the exploration of their central gameplay mechanic; heck, there's not even any permanent death in Polarity, so the player is free to experiment and learn about the use of the magnetism. These games are about being interesting and immersive rather than necessarily being balls-out challenging (neither Polarity, Portal, Fez, nor Braid have any puzzles which we might define as truly, mind-numbingly difficult).
To be honest, I've sort of lost track of what I was trying to say. In summation:
-Games revolving around single gameplay mechanics are cool.
-Indie games do this far more frequently, and often more effectively than mainstream titles.
-Polarity is fun, and worth a download.