Quantum Theory

However, in the wasteland, there are strange towers that have appeared.

Seemingly sentient, nobody knows who built them or why, only that anyone who ventures near will know only death.

From these towers comes a mysterious substance called diablosis, which corrupts those who touch it, turning them into murderous killing machines.

One man, known only as Syd, has made it his mission to destroy these towers and stop the diablosis.

Quantum Theory is a a cover-based third-person shooter similar to the popular Gears of War series .

Syd can hide behind and fire from cover, as well as "roadie run" between cover to move closer to enemies.

He can carry up to three different weapons at a time, as well as go face-to-face with a powerful melee attack.

Syd will also team up with a woman named Filena, with whom he can perform special team attacks, and even throw her at enemies for an especially powerful attack.

In addition to the single-player campaign, there are also online team and deathmatch multiplayer modes.

Quantum Theory for Xbox 360 is currently worth €15.82 loose, €11.69 complete in box, and €27.48 factory sealed. Prices are based on real sales and update regularly on Gamevaro.

Quantum Theory has a steady sales history on the tracked marketplaces, meaning it trades hands regularly and isn't considered particularly rare.

Loose means cartridge or disc only, CIB (complete in box) includes the original box and manual, and sealed means factory-sealed and never opened. For Quantum Theory, loose is €15.82 and CIB is €11.69 — CIB commands a premium because original boxes and manuals are fragile and often don't survive.

The PAL version of Quantum Theory is currently worth €15.82 loose, versus €13.06 for NTSC-U. Regional price differences usually come down to print run size and regional collector demand.