CLOBBER is a new combinatorial game invented last summer in Halifax by Michael Albert, J. P. Grossman, and Richard Nowakowski. The first competitive CLOBBER tournament was held at Dagstuhl, Germany, in February 2002.

Clobber is played by two players, white and black, on a rectangular n x m checkerboard. In the initial position, all squares are occupied by a stone, with white stones on the white squares and black stones on the black squares. A player moves by picking up one of their stones and "clobbering" an opponent's stone on an adjacent square (horizontally or vertically). The clobbered stone is removed from the board and replaced by the stone that was moved. The game ends when one player, on their turn, is unable to move, and then that player loses.

The game typically decomposes into many smaller positions. Values of some of these positions have been cataloged at

Tools for further study of clobber and other games are available at

This note annoounces a $1,000 (Canadian) PRIZE FOR THE BEST CLOBBER PROBLEM COMPOSITION(S).

At least one winner will be announced at the following meeting:

   Third International Conference on Computers and Games
   Edmonton, Canada, July 25-27 2002

If many outstanding problems are submitted, there will be more than one prize. The winning problems and their solutions are intended to be published, with commentary by the judge(s).

A composed problem must specify a position and which player is to move next. Each submission must also be accompanied by a solution proposed by the composer. Although the solution might include a modest number of computer-generated values, figures, or tables, it must be intelligible to humans who have no access to any machines. The solution should indicate how to play against all plausible opposing strategies. Ideally, the proof that the solution is correct should also require no machine assistance.

Difficult-yet-elegant problems which utilize combinatorial game concepts such as atomic weights and/or thermography are especially welcome. (e.g., See the Childish Hackenbush "Lollipops" problem in Chapter 8 of Winning Ways.) It is very desirable (but not required) that a problem have a history going back to the conventional starting position. The board size must not exceed 10 x 10. Smaller board sizes are more desirable unless they entail excessive compromises with the primary goals of difficulty and elegance.

Any entry, including solution, should not exceed three 8.5 x 11 inch pages. To be eligible for a prize, an entry should be submitted by email to

and must be received before 11:59 pm, PDT, on July 20, 2002.