Underscan is a interactive video art installation designed by Rafael Lozano-Hemmer to be shown in a public space. Passers by are detected by a computerised tracking system which activates video portraits projected on the pavement within their shadow. The people depicted in the videos lie dormant until the shadow of a passer by moves over them, then they start moving. The inspiration for the work was a study of shadows. We saw the installation in Trafalgar Square outside the National Gallery. I thought the images would be more interactive, but on the evening we saw them the videos just seemed to run at random intervals it was difficult to activate them and others ran for several minutes whether people were interacting with them or not.