sapphire-chess (rubygems):     Sapphire Chess is a command line-based chess game with an algebraic notation input system,     complete chess rules, a beautiful interface, and a functional AI. It provides three game modes:      Human vs. Human, Human vs. AI, and AI vs. AI. 
Keywords: ai|chess|chess-board|chess-engine|minimax-algorithm|minimax-alpha-beta-pruning|ruby