Airsoft is a team game in which participants eliminate opposing players by pelting them with plastic pellets fired from air weapons called airsoft replicas. Although very similar to paintball in concept and gameplay, airsoft balls leave no visible marks on their target and hits are not always obvious. The airsoft guns in use are mostly magazine-fed, with some having manual/battery-powered spring-piston pumps or pneumatically actuated replaceable compressed gas (eg propane ("green gas"), -tetrafluoroethane or CO2) magazines. Many airsoft guns also have mounting platforms compatible with original firearm accessories and cosmetically more like real firearms. This makes them popular for military simulations and historical reenactments.