Reach Chess is a chess variant discovered by accident while testing the Ludii general game system, in which a simple rule change fundamentally subverts the nature of the standard game. This paper describes Reach Chess, how it came to exist, and reveals its character through a brief analysis and puzzle with annotated solution.

This paper introduces bitwise-parallel reduction (BPR), an efficient method for performing connection tests in hexagonal connection games such as Hex and Y. BPR is based on a known property of Y that games can be reduced to a single value indicating the fully connected player (if any) through a sequence of reduction operations. We adapt this process for bitwise-parallel implementation and demonstrate its benefit over a range of board sizes. BPR is by far the fastest known method if connection tests only need to be performed once per game, for example, to evaluate board fills following Monte Carlo playouts.

Monte Carlo tree search (MCTS) is a recently proposed search method that combines the precision of tree search with the generality of random sampling. It has received considerable interest due to its spectacular success in the difficult problem of computer Go, but has also proved beneficial in a range of other domains. This paper is a survey of the literature to date, intended to provide a snapshot of the state of the art after the first five years of MCTS research. We outline the core algorithm's derivation, impart some structure on the many variations and enhancements that have been proposed, and summarize the results from the key game and nongame domains to which MCTS methods have been applied. A number of open research questions indicate that the field is ripe for future work.