I see it's still up after 20+ years: NeHe at https://nehe.gamedev.net/

In 2005-ish I followed what is now called "legacy tutorials" and I just learned a lot about how rendering pipeline works in OpenGL + some basic 3d math and physics. The rope tutorial (https://nehe.gamedev.net/tutorial/rope_physics/17006/) was my favorite.

Also, my highschool math teacher was in awe when I was so familiar with vector math and matrices and it was so easy to grasp the concepts in class because I could visualize everything. This is a nod to a previous post here on HN: https://news.ycombinator.com/item?id=40983734