This first issue of the International Journal of Game Theory is dedicated to papers in the field of Combinatorial Game Theory (CGT). Combinatorial games are traditionally two-player perfect-information games with compact rules (typically only win or loss as outcomes, and no chance moves), and a rich mathematical structure. As reflected in this special issue, activity in CGT accommodates a sprinkling of deviation from this tradition, such as infinite and cyclic games, games with a winning score, or one-player and multi-player games, which freshens up the theory.
In Lisbon, under the auspices of Associação Ludus, Carlos Santos has been organizing the “Combinatorial Game Theory Colloquium” taking place every two years starting in January 2015, 2017, and next in 2019. Some of the papers in this special issue have been presented at the first colloquium in 2015. It is the editorial policy of IJGT that all submissions are thoroughly reviewed and screened for quality, so this is not a proceedings volume, and the special issue has the same high publication standard of IJGT as any other. The majority of the papers in this issue have in fact been submitted independently of the colloquium.