We present Flex-Beam, a novel projection system designed to enhance and simplify the process of creating projections for digital performances. This system features a motorized reector to move the projection image as being mounted on a projector and a mobile application to control the system easily without complex interfaces. We evaluated the usefulness and competence of Flex-Beam through three examined interactions for actual live performances: control of the projection position, utilization as a dynamic stage lighting, and creation of a real-time interactive image in motion. The results present that Flex-Beam as an easy-to-use and affordable alternative in digital performances can cover the wide display area with only a projector and create a moving stage lighting/scene regardless of the configuration of a theatre space.