A cover system is disclosed that comprises at least one cover sheet having four edges; a plurality of flexible rafters, each of the rafters is slidably connected to at least one of two opposite edges of the four edges; and at least one roller provided on at least one of two other opposite edges of the four edges, wherein the roller is configured to rotate, and the cover sheet is configured to wrap around the roller and be released from the roller, depending on a direction of rotation of the roller.