First, both versions of the game have the same challenge related to the way Vuforia handles locations of different targets. All targets tracked by Vuforia have their own coordinate system, with the origin being in the center of the target. In regular 3D games the coordinate system is typically uniform for all objects which make for example collision detection easy. In the first prototype we had to take the model view matrix of target A, invert it, and then multiply it with the transposed model view matrix of target B. This created an offset matrix with which one can multiply by points in 3D space to produce the coordinates in the other target's coordinate space. This entails more calculations that are required for something as common as collision detection, so the matrix calculation algorithms should be highly optimized.