GTA IV PHYSICS ARE NOW IN SKYRIM 🚨 Skyrim Delirium swaps the game's limp ragdolls for living ones, just like GTA IV. It's powered by Delirium, an open-source engine that recreates the Euphoria-style physics behind GTA IV, adapted to work in Skyrim. NPCs stagger, fight to keep their balance, clutch their wounds and stumble the way the hit pushed them. Fire makes them writhe, shock makes them convulse and frost makes them seize up. Unrelenting Force sends them flailing through the air. Kill moves are gone too, so every death plays out physically.