A one-level (okay, two if you count the intro room) demo of an upcoming scenario. Portal of Sigma is a Big House inmate, and a promising one. The mapmaking in this demo is gorgeous. Terms need a little work, and the gamplay is rather linear... but both of those will change in the final product - he leads you where he wants you to go... it's a demo, after all. After playing through the level, the first word that came to mind was 'clean'. I think you'll like it.