When I first started learning about game design, it seemed like there were new revelations every day. By now, the low-hanging fruit is gone. I still learn things every day–but the lessons are narrower.
It’s possible to do a double-sided single 3D plane in Unity, but it requires writing a custom shader, or at least customizing an existing one with the “Cull Off” command.
Git and SVN offer much the same basic functionality, albeit under different names. Many of the best practices for using each are the same.
Adobe has a great collection of color swatches here.
So much of doing good work, in the law or in game design, is in the details. These lessons aren’t as sweeping as the early ones, but these smaller building blocks are valuable–they fill in gaps that could otherwise show through in a final product.