It's built in Unity. Luc did a great job with the art style.
I presume you like the look of the characters? The shaders are pretty much all plain colours using Unity's standard shader, we've just added a lot of emissive colour (to make them glow from inside) and also put a lot of lights in the scene and kept the shadows very soft. Luc also baked in some shadows into the character and on top of that there's some soft ambient occlusion on the camera (using Unity's built in ambient occlusion)
Viewing post in Eat The Rich (Black Friday Simulator) comments
The characters are all animated with physics, but I've got some traditional animations that the joints are trying to follow. A bit like how the Unity addon "Puppet Master" works.
i.e. There are normal animations being played and the joints are adding forces to try match the rotations of the normally animated character.