GTA IV är det första spelet i serien som använder sig av en avancerad motor. Tekniken heter Euphoria och möjliggör naturtrogna och auomatiska animationer, självtänkande A.I och verklighetstrogen fysik på objekt. Möjligheterna kommer således bli oändliga och det kommer bli oerhört mycket roligare att leka runt och experimentera i Rockstars sandlådevärld.


En demonstration som visar kraften i Euphoria-motorn

Några stycken ur en förhandstitt på GTA IV som inte direkt fick tiden att gå snabbare:

In a more practical, action-oriented setting, enemies are also imbued with Euphoria's influence. When Niko is unloading a clip into his adversary, none of the reactionary movements to the hot lead are canned or scripted. The hapless bad guy recoils naturally in response to being struck by the bullet. Wound him enough and he'll fall backwards, slouch on the ground or start to try and crawl away to cover with his last ounces of strength. Shoot him on a ledge, and he'll topple backwards or lose his balance and plummet, arms waving, to his death.

Niko, as well as enemies in the game, are affected by inertia ? to the point where rear-ending a car causes people in the front to fly through the windshield and into the air, arms in a controlled flail. The impact is sickening and realistic; bodies don't just ragdoll in GTA IV, they roll end over end or side-on, before coming to a natural pause. If you're still alive, Niko will gingerly pick himself up and you can be on your way.

The AI also reacts to weather conditions. During one jaunt through a seaside park area (reminiscent of Salvatore's mansion, in the old northeast end of the Saint Mark's district in GTA III), we witnessed a woman break into a jog and pull her shawl close around her. Moments later, a storm front rolled in and the rain came down. That's pretty impressive stuff right there.