Catchup is a territory game invented by Nick Bentley in 2011.

Terminology
  • Group: a set of connected, like-colored stones on the board.
  • Group size: the number of stones that a group contains. The smallest possible group has a size of 2. The diagram on the right shows a singleton and two groups with sizes 3 and 12.
  • To drop: to place a stone on any empty space.

Rules
The game starts on an empty board. There are two players, white and black.

Initial positionInitial position
  • One player owns the white stones and the other owns the black stones. The players take turns. White begins by dropping 1 stone. From then on each player must drop 1 or 2 stones on his turn.
  • If a player on his turn makes a move that results in a group that is larger than the largest group, regardless of color, that existed at the beginning of the turn, his opponent may drop up to 3 stones on his next turn (and only on his next turn).
  • The game ends when the board is full. The player with the largest group wins. If the players’ largest groups are the same size, compare their second-largest groups, and so on, until you come to a pair which aren't the same size. Whoever owns the larger of the two wins. Catchup cannot end in a draw.

Alternative rules
The alternative rules are as above, with the following difference: On a turn, a player must perform exactly one of the following actions:
  • Place one stone on an empty cell of the board.
  • Place two stones on empty cells of the board, in such a way that the size of the largest group on the board at the end of the turn is the same as it was at the outset of the turn.

If you start up a Catchup game, you will have the option to choose these alternative rules, that were suggested by Luis Bolaños Mures.

Note
Catchup is a territory game using a somewhat unusual definition of territory. As long as they differ in size, players' territories consists of their largest groups. If these are the same size, then players' territories consists of their largest groups plus their 'next in size' (which may be the same size as the previous one), unless these territories are equal in size too, in which case the groups next in size are considered and so on, till an unequal territorycount results. A very strong incentive to always keep an eye on the overall situation, and not focus on the largest group alone.

Sorry, you need a Java enabled browser to view this Catchup Game.
Example game
(original rules)























Using the Catchup applet
External links

Catchup © Nick Bentley
Java applet © Ed van Zon