Paintball is a sport in which players compete, in teams or individually, to eliminate opponents by tagging them with capsules containing water soluble dye and gelatin shell outside (referred to as paintballs) propelled from a device called a paintball marker (commonly referred to as a paintball gun). Games can be played on very hard floors in indoor fields, or outdoor fields of varying sizes. A game field is scattered with natural or artificial terrain, which players use for tactical cover. Game types in paintball vary, but can include capture the flag, elimination, ammunition limits, defending or attacking a particular point or area, or capturing objects of interest hidden in the playing area. Depending on the variant played, games can last from seconds to hours, or even days in scenario play.