A system for controlling light in a facility may include at least one rail longitudinally affixable to an inner portion of a frame of the facility between a first end and a second end of the facility and at a rail-height above a floor of the facility； and at least one opaque/reflective covering tightly and opaquely affixable to the inner portion of the facility frame at a cover-height above the facility floor in a first plane that faces the facility floor and slidably connectable to the at least one rail, the at least one opaque/reflective covering being extendable along the at least one rail between a first covering position and a second covering position to opaquely cover respective at least one longitudinal section of the facility in the first plane when in the second covering position, without substantially covering the facility walls.
