Platform is a damned remarkable game. Not only does it combine pimpass platforming puzzles with a Lost Vikings-esque character separation mechanic, but it's also the only episodic series I can think of which manages to be just as prolific as most webcomics.
Since May 2nd, 2007, Platform's creator released a new level every Sunday (more or less) until this most recent one, wherein he finally completed the game.
Truth be told, I wish I could have spotlighted Platform when it was still incomplete so you could look forward to it on a weekly basis; still, though, it's nice that the game can now be played from beginning to end in one sitting. You should go here and play it immediately, for reasons I shall explain after the jump.
Super Mario plus Lost Vikings plus Portal equals Platform. This noble little flash game takes the great platforming of Mario, mixes it up by forcing the player to simultaneously control two different characters to complete multiple tasks, and sets it in an impersonal, alien, and sterilized world which should be familiar to all disciples of GLadDOS.
The two protagonists, a blonde and a brunette, wake up in some sort of testing chamber with no memory of who they are or how they got there. Having nothing better to do than trudge onward and explore, the two set out to find some answers.
Platform controls very simply: arrow keys move, Z key jumps, and spacebar switches characters. Initially, the rooms are pretty safe and easy to get through: rooms 1-3 don't really require that much timing or cooperativity so much as they force the player to engage in some mildly challenging platforming with one character, then switch to the other and do it all again. As each level is only a single screen, repetetiveness is never really a problem.
After the player acclimates himself to the player-switching mechanic, however, the creator begins to really explore its possibilities. On level six, for instance, one character has to stand on a stationary platform and jump over a buzzsaw once it starts moving, while the other has to go down and flip the switch while avoiding his own moving buzzsaw. What initially seems purely strategic turns out to be incredibly intense, as the player takes control of one character, jumps over the switch saw, hits the switch, immediately switches to the other character, jumps over that saw, then switches back and jumps over the saw again. The game requires quick wits to figure out what to do, and quicker reflexes to actually do them.
Every three levels, the masters of the factory introduce a new gameplay element. Though some of the gameplay additions work better than others (the jetpacks are a bit dull), this rule of 3 adds an incredible amount of variety and excitement to the gameplay. I remember someone on the commentary for Half Life 2: Episode One said that the average player needs three stages of gameplay to acclimate to a new mechanic: one to introduce it, one to test the player's knowledge, and one to flip the mechanic on its head. Platform does this quite brilliantly, and quite frequently.
What I really love about Platform is that even if you took away the entire two character aspect of the game, you'd still have an incredibly clever, fun, polished product. Even if all the multi-person puzzles were chucked, the platforming controls are still really solid; even without the platforming, many of the puzzles, while simply designed, are challenging and fun. With the second player, however, the game takes on an entirely new dimension.
Again, though, I really wish I had found Platform while it was still coming out on a weekly basis. Looking at the level archives, I've developed a great deal of respect for the guy who created the game (I can't seem to find who he actually is -- the game's website doesn't have his name anywhere, and typing "platform game" into Google gets a lot of unrelated results, as you might assume); apart from missing a week or two here or there, the guy was incredibly faithful to his promise of releasing one new level every Sunday. I can only hope that he starts another episodic game series of some sort, or that somebody borrows his idea. I would absolutely love to wait for a new level of something like Platform on a weekly basis.
But yeah, play it and enjoy it. It's a simple flash game, doesn't require any downloading.