WASHINGTON – When robots play soccer, it looks like a game played by 5-year-olds: they swarm around the ball, kick haphazardly and fall down a lot. However, robot teams have made strides in recent years, and some researchers believe the humanoids could challenge the world's best players in a decade or two. "Maybe in 20 years we could develop a team of robots to play against the best World Cup teams," said Daniel Lee, who heads the University of Pennsylvania robotics lab, which is seeking a fourth consecutive RoboCup in Brazil this month, the premiere event for robotic soccer. Robotic soccer, says Lee, is more than fun and games. It involves artificial intelligence and complex algorithms that help provide a better understanding of human vision, cognition and mobility.