It is sometimes necessary to fine-tune a city's production. To do so, you'll want specialists. Specialists do not work in the city radius so they don't contribute to city production of food or commerce. Instead, they produce extra happy faces, enhance scientific research, tax revenue, or shield production, or help control corruption. Entertainers An entertainer produces one happy face. Scientists A scientist produces extra scientific research. Tax Collector A tax collector produces extra tax revenue. Police Officers Once Nationalism has been researched, a police officer can be used to help keep a lid on corruption in a city. Civil Engineer Once Replaceable Parts has been researched, a Civil Engineer can be used to produce additional shields which can be applied toward the production of city Improvements and wonders. To create one of these specialists, on the City Display, click any square currently being worked; the production icons disappear and an Entertainer appears among the population. If you wanted an entertainer, you're done. If you wanted a different specialist, click on the entertainer to cycle through all the specialists. Note that Police Officers and Civil Engineers are not available until Nationalism or Replaceable Parts (respectively) have been researched.