In Spiderball4k, the goal is to guide a ball to the end of the level by firing ropes with your mouse. This may seem easy, but it is in fact a lot trickier than it appears.
Play Spiderball4k (Java Webstart)
Website (with instructions)
Spiderball4k was the overall winner of the 2008 Java4k competition.
Tomas Alaeus (Don) helped create the website and replay version.