However, Sonic Unleashed made significant improvements and additions to the Hedgehog Engine 2, including:
* New physics system: The game featured a new physics system that allowed for more realistic movement and interactions with the environment.
* Enhanced graphics: Sonic Unleashed boasted improved graphics and visual effects compared to its predecessor.
* New gameplay mechanics: The game introduced new gameplay mechanics such as the "Werehog" form and the "Day" and "Night" levels.
* Improved AI: The AI in Sonic Unleashed was significantly improved, making enemies more challenging to defeat.
So, while Sonic Unleashed did not introduce a completely new engine, it did make significant changes and improvements to the existing Hedgehog Engine 2, resulting in a vastly different gameplay experience.