Breakable Objects and Foliage: Remember Red Faction? One of the first shooters to support wanton environmental demolition, but still very much "destruction on a leash," and no one's really bothered to expand much since. (Too unpredictable, that's what devs will tell you. Or "does nothing for the gameplay."). In Crysis it's all about the gameplay, and the CryENGINE2 scales it to entirely new levels, offering randomly breakable objects, trees, and wholesale buildings. Imagine running a bulldozer into a shanty and watching the walls randomly buckle, the roof shingling fall apart in pieces, and the sides cave at different angles. Crytek's rule of thumb: if it looks destructible, it probably is. Trees, too. Launch missiles at palm trees and witness them crack apart at arbitrary points; as the tree top falls, the leaves hit the ground and bend or fan in direct proportion to their angle of impact. And watch your backtrail -- too much bending of grass near enemies and they'll notice...and hunt you down, now based as much on visual as aural evidence of your transgression.

Backlighting: Leaves are translucent in real-life, but games like to pretend they're just static objects or flat-textures, thick as steel. Backlighting in Crysis allows shadows and light through the physical structures of light-permeable objects.

Caustics: Just a fancy name for improved light refraction. You remember your physics, right? The index of refraction was that annoyingly arbitrary number assigned to light-bending substances like plastic or glass or water. Light goes in at one angle and bends in another (ergo toys like the magical wonderful prism!). In Crysis caustics model the refraction of photons as they pass through surfaces like water and scatter on the sea floor, producing the wavy-glow effects you get in swimming pools or near shoreline through exceptionally clear water.