Gravity. Physics. Lines of sight. Reflections. This is the sort of 'invisible' imagery that forms the focus of this year's Leuven-based STUK festival, and even if you can't attend, the fest's site is worth perusing for its curation of works that hinge on tensions between visibility and invisibility, or presence and absence. Classic internet art works like John F. Simon Jr's 'Every Icon' and Vuk Cosic's 'ASCII History of Moving Images' join important media art works by Zoe Beloff, Jim Campbell, Michael Snow, Sam Taylor-Wood, and others. In total, seventeen artists will present installations from February 13-18, including newer works by Rafael Lozano-Hemmer, Wim Janssen, Victor Kossakovsky, and Workspace Unlimited. Their projects take up special effects, optical novelties, and often paranormal subjects and ephemera. STUK will also feature a symposium on locative media and live art by thirteen international new media performance artists. The organizers say that 'STUK is filled with empty, but promising spaces, images and constructions.' Certainly this emptiness offers much to behold, and it's promised that many of the interactive art works will return your gaze. - Elizabeth Johnston