In this paper, we address a natural question at the intersection of combinatorial game theory and computational complexity: “Can a sum of simple tepid games in canonical form be intractable?” To resolve this fundamental question, we consider superstars , positions first introduced in Winning Ways where all options are nimbers . Extending Morris’ classic result with hot games to tepid games, we prove that disjunctive sums of superstars are intractable to solve. This is striking as sums of nimbers can be computed in linear time. Our analysis shows that the game Paint Can is intractable and also yields a new intractable game, Blackout . We present web-playable versions of both games.

Snort is a two-player game played on a simple graph in which players alternately colour a vertex such that they do not colour adjacent to their opponent’s vertex. In combinatorial game theory, the temperature of a position is a measure of the urgency of moving first. It is known that the temperature of Snort in general is infinite ( K 1 , n has temperature n ). We show that for all constants c there is a game of Snort for which the difference between the temperature and the maximum degree of the board is at least c . We do so by constructing a family of positions in which the temperature grows twice as fast as the maximum degree of the board.