A 2D and 3D physics engine implemented in C# with XNA. The engine is a heavily modified version of Millington’s engine and is able to provide efficient handling for physics simulations, implementing an impulse force collision modelling to deal with rigid objects. Other physics-based motions such as springs, ropes, and hard constraints, water, ragdolls can also be simulated in CRUST. The engine is also facilitated with a friendly user interface that allows editing objects and their physical properties at runtime. A version of Crust was used in implementing a 3D augmented reality environment to interact with physics objects in realtime.