Vigil Games are a class of strategy games in which players must maintain an uninterrupted line of sight between their pieces and a designated reference point or region of the board. The first vigil game on record is 1892's Kastellet. Sentinel is a vigil game where players always need to have at least one line-of-sight to the board's center. Sentinel is the second abstract game of this genre (after more than 130 years!), mixing typical movement and capture ludemes with permanent line-of-sight control of the central square. The game mixes forward movement with sowing stacks which are the only way for armies to increase their size. Complete rules at the game's forums. —description from the designer

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