* Some abilities are mutually exclusive, like walking vs flying vs swimming vs parachute flight * Some abilities can be enabled manually (opening parachute or flying with jetpack), others can be enabled by environment (underwater areas) * Are they mutually exclusive? Can the player walk underwater if he stands on the bottom? * Can a parachute be opened while walking on land? * `player.register_control_ability(Walk, exclusive=true)` ? * State machine built into `UP_BasePlayer` or customizable outside?
