Maven (Scrabble) on Scrabble. The problem with Alpha Beta is that some Scrabble endgames require 14 moves to play out, and it is not possible to search that deeply. This is not merely a theoretical possibility. When one player is "stuck" with a tile, then playing out all remaining tiles is impossible. In that situation the optimal strategy for both sides is usually to play one tile on each turn. Maven uses a different approach. The B* search algorithm is a selective-depth, progressive-widening algorithm that guarantees to find optimal solutions to two-player games when one can compute upper and lower bounds on
Challenge (Scrabble) has not seen a single drawn tile yet, in order to consider whether to challenge. To do this, the player simply announces, "Hold," which prevents the opponent from drawing replenishment tiles for 15 seconds (but may draw thereafter, keeping those tiles separate). The player may decide to rescind the hold, or challenge the play. Scrabble and Scrabble-like game sites on the Internet such as Yahoo! Games' Literati, Internet Scrabble Club and Lexulous offer automatic verification as an option, which makes it impossible to play an invalid word. The Facebook version of Scrabble and Zynga's mobile game Words With Friends make