I often have this feeling when I read Mike's code, particularly D3. Then I read the code again and work to understand it and I learn something new myself. Mike's coding style leans to very terse; one letter variable names, fearless use of operator precedence and side effects. It requires you understand the language to read it clearly, but the advantage is a lot more code fits in a small space. His code is quite poetic, it's a nice change of pace from Java verbosity. (My favorite cosmetic idiom he uses: non-ASCII variable names for spherical trigonometry: https://raw.github.com/mbostock/d3/master/src/geo/conic-equi...)