How to create applications that look right, behave properly, and fit into the GNOME user interface as a whole, covers specific advice on making effective use of interface elements, and the philosophy and general design principles behind GNOME interface.
By Evan Miller. essay about how you can get paid to write great open-source software. If you're not a software developer, you should probably spend the next few minutes of your leisure time on a web page other than this one.
Whilst the puzzles here are mainly lateral thinking puzzles, they range from the image type puzzle shown here, through to riddles and other puzzles. Overall, they provide somewhere to exercise the brain muscle and have fun.