Movement is done through "zones"-- for the sake of simplicity, generally speaking one room (or in the case of something large like a hangar bay, one corner of the room) equals one zone.  Characters can either move once from one zone to another and take an action, or sprint to move twice.  Melee range is within the same zone as an enemy, Close range is the next zone over, Medium range is two zones, and so on.  You still need line-of-sight to be able to shoot things at range, obviously, but stuff like Motion Trackers can work at Long or Extreme range without needing eyes on the target.