Methos are being developed to at least approximate perfect poker strategy from the combinatorial game theory perspective in the heads-up (two player) game, and increasingly good systems are being created for the multi-player game. Perfect strategy has multiple meanings in this context. From a game-theoretic optimal point of view, a perfect strategy is one that cannot expect to lose to any other player's strategy; however, optimal strategy can vary in the presence of sub-optimal players who have weaknesses that can be exploited. In this case, a perfect strategy would be one that correctly or closely models those weaknesses and takes advantage of them to make a profit. Some of these systems are based on Bayes theorem, Nash equilibrium, Monte Carlo simulation and Neural networks. A large amount of the research is being done at the University of Alberta by the GAMES group led by Jonathan Schaeffer who developed Poki and PsOpti. The Poki engine has been licensed for the entertainment game STACKED featuring Canadian poker player Daniel Negreanu. "PsOpti" is available under the name "SparBot" in the poker training program "Poker Academy".