Police Quest and SWAT are a series of computer games produced and published by Sierra On-Line between 1987 and 2008. The original Police Quest series was composed of three adventure games designed by former policeman Jim Walls, and a fourth title designed by Daryl F. Gates. The later games in the series resulted in the renamed SWAT series. The adventure game decreased in popularity by the mid- nineties and Jim Walls, the former series designer, left Sierra and was replaced by real-life SWAT founder Daryl F. Gates. After Gates released Open Season, Sierra searched out new genres for the popular police simulation series.