I ran into this little game earlier, and found it to be an interesting little test of reflexes. I could only last about 11-12 seconds, but most of my friends did MUCH worse. Try it and see how you do, I want to know if I'm really good at this or if I just have retarded friends.
http://members.iinet.net.au/~pontipak/redsquare.html
http://members.iinet.net.au/~pontipak/redsquare.html