Halo is composed of four interactive video projections using very powerful high resolution video projectors and four computers with an infra-red remote visual sensing system for viewer interaction. On each screen is visible a number of figures. Each figure is individually interactive, with the audience and with each other. The piece uses object oriented and behavioural programming techniques.
Each figure is individually interactive and the viewer is fully modelled within the interactive system. A gravity well forms around each viewer, attracting flying figures into their orbit. When the viewer approaches the screen the figures are 'pulled' down to earth, where instead of flying they walk in direct interaction with the viewer. A number of interactive texts using generative grammars, based on the textual works of William Blake, are visible on each screen.
(Source: Project description from Biggs's site)