Despite its widespread popularity in East Asia, Go has been slow to spread to the rest of the world, unlike other games of ancient Asian origin, such as chess. Schadler speculates that chess has more widespread appeal because culturally congruent game pieces can be created in chess (e.g. Queen and Bishop in Western Chess, Advisor and Elephant in Chinese Chess), while Go is totally abstract. Also, there is no climactic ending in Go (such as checkmate in chess). New players often have trouble figuring out when a game of Go is over. Other theories center around the existence of fundamental differences in the level and type of thinking required by Go players as opposed to chess players. While pure analytical thought and the ability to plan many moves in advance are advantageous in chess, in Go a more intuitive approach based on pattern recognition and experience is stressed. A purely analytical approach, due to the sheer number of moves available for consideration, can be paralyzing.