Here's a PSPACE-complete puzzle game I created, if anyone is interested: https://docs.google.com/leafid=0B7zc3Wqisi4jNTE5NTU0NGQtZjdiOS00OWIxLWFlMjct... You can design your own levels (and upload!), which can be as complex as any linear-bounded automaton (Turing machine with bounded memory). One of my default levels contains a 15-puzzle built into it. There are 40 default levels, and you can upload an arbitrary number to the Internet from within the program. Also, if anyone here has Golly, the levels are in Golly's Extended RLE format, so you can additionally create and edit levels from within Golly. Please enter a *unique* username when prompted, so that you don't overwrite someone else's highscores, etc. That's happened before with two people called 'Dave'... Have fun! Sincerely, Adam P. Goucher