Originally, the soccer field had a grayscale plastic floor allowing the robots to locate themselves along the field. In 2007, this was replaced with the GENII (Generation 2) field which had different shades of green plastic, which allowed light sensors to be used to more accurately determine location (this field is still used in Australia, New Zealand, and is now also used in the World Robot Olympiad). In 2009, the field was replaced with plain green felt. This change was aimed at making the game more realistic by creating greater reliance on the goal location and walls rather than the ground. The change, however, has been controversial with many teams having problems with quality of the felt.