3. PLAY TRACER
A natural way to think of player movement in arbitrary games is the path they take between different game states. A play trace is then a path that a player takes in this high-dimensional game state space. In order to visualize these paths, we use Classical Multidimensional Scaling (CMDS) [3, 17] to represent observed game states in two dimensions. CMDS takes an input matrix that specifies the distance between every pair of states and outputs a set of points, which are positioned to minimize a loss function on all inter point distances. Therefore, the transformation will place states that are similar close together and states that are dissimilar far apart, making it easy to see the similarity of states that are visited by many players. We used the MDSJ library for Java [18].