Interferometry enables some of today’s most advanced astronomical imaging, yet its principles are hard to explain to audiences used to conventional cameras and telescopes. Lego ALMA is a tangible exhibit where visitors move antennas and discover how array configuration shapes image formation, usually guided by an expert. Building on earlier work in Bonn, Vienna and ESO, we redesigned an installation at Onsala Space Observatory. Using successive prototypes and iterative testing with 150 users (mainly school classes, ages 8 to 17) we simplified the interface and added animation based guidance, successfully enabling independent exploration, and increasing engagement with interferometry concepts. Most visitors needed no assistance, though some prioritised physical play over on screen cues.