As a matter of fact, the gameplay engine, the physics, the controls (with some minor changes for the 360 controller and the aspect ratio) are identical. It is, in short, the Halo CE engine, but with a second graphics layer, a separate engine in fact, running on top. You can see this phenomenon yourself by pressing the back button at any time. The game will switch from old graphics to new, and back again, in real time. That in itself, is a bizarrely fun feature – one we constantly used to check to see if things truly were identical, or more frequently, simply to compare the two generations of hardware and see how far things had come. Although perversely, sometimes we switched back only to remember how good the original looked.
Read the whole article over at Xbox.com.