Valve has admitted that while developing Portal 2, it was considering making a game that didn't have portals. While they eventually backed away from that line of thinking, Quantum Conundrum is likely the game that they would have made had they continued working on their prototype.

Square Enix's upcoming downloadable game comes from Kim Swift, designer of the original Portal. As you move from test chamber to chamber, it's hard not to make comparisons between it and Valve's classic.

The similarities are almost too numerous to write up. Yes, you are, for all intents and purposes, trapped in a series of test chambers. Moving from one to the next usually involves figuring out how to open a door--one controlled by an elaborate setup of pressure plates and buttons and switches. As you progress through the game, you have a chatty guide telling you how to use the various machinations of the facility.

There is one key difference between Quantum Conundrum and Portal, however. This game's narrator, Professor Fitz Quadwrangle, is far more encouraging than the sinister GLaDOS.

Whereas Portal's gimmick was the ability to connect two points with portals, Quantum Conundrum is harder to define. You have access to a number of "universes," each which affects the world in a specific way. Switching between these universes is how you make progress in the game's test chambers.

In the pre-E3 demo I played, I only had access to one universe: the fluffy universe. By turning this universe on, the entire world turns white, looking like plush mattresses. In this world, every object becomes lightweight. Crucially, iron safes become pillows--and switching their weight is key to solving the game's first few puzzles.

For example, in one room, you can hit a switch that makes a safe launch towards a room you are in. Unfortunately, it doesn't have the momentum to reach you. By switching to the fluffy universe, the safe flies towards you--only to be stopped by glass that protects you. With its reduced weight, it can make the jump, but it can't break through the glass that protects your room. Timing is key to solving this conundrum. As the safe lifts away from its launcher, switch to the fluffy universe. As the safe reaches your room, switch back to the normal universe, restoring the safe's deadly weight--enough to shatter through the glass room you were trapped in.

Presumably, the addition of other universes will make Quantum Conundrum far more complex, and far more satisfying to solve. But having access to all the game's powers would probably make for too intimidating of an E3 demo. These first few levels show off the game's puzzling potential, but I wonder if Qunatum Conundrum can surprise us much like Portal did--with writing that was as clever as the puzzles themselves.

Quantum Conundrum will be available on PC, PlayStation Network, and Xbox Live Arcade later this year.

Watch the Shacknews E3 2012 page to follow all our coverage of this year's show. This preview is based on a hands-on demo shown at a pre-E3 event.