Editorial: Many games, many authors

The last issue of this roller-coaster year contains three scientific articles. The first one, Polygames: Im-proved zero learning , counts 24 authors, which is probably the highest number since the establishment of the journal. The article presents P OLYGAMES , an open-source framework that combines Monte Carlo Tree Search and Deep Learning. The framework is generic enough for implementing many games, being size-invariant, and comes with a games library included. P OLYGAMES won against strong players in the game of 19 × 19 Hex and 8 × 8 Havannah. Fewer authors has the second contri-bution, Analyzing a variant of Clobber: The game of San Jego , by Raphael Thiele and Ingo Althöfer. It introduces a new two-player perfect-information game, called San Jego. The authors establish an upper bound for the state-space complexity and approximate the game-tree complexity. For small board sizes, they calculate the optimal game-theoretic values and investigate the advantage of moving first. Games are fun but can also be used more seriously as the third contribution, A polyomino puzzle for arithmetic practice , by Jeremy Foxcroft and Daniel Ashlock, shows. The article proposes a family of puzzles that gamifies arithmetic skills. The puzzles are designed with an evolutionary algorithm forming an instance of automatic content generation. It a review , con-ference TCEC and