Tangentially related, I've been extremely impressed following 3DSage's work. I've only dipped my toe into GBA programming ("hello world"-level stuff), and the fact that they built a real-time 3D level editor is mind-blowing to me.
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The editor and looking at another video from sage3d also the rendering method, seems extremely reminiscent of duke3d. You can see a review of the duke3d rendering and sector setup on Fabians page.
Why the Tomb Raider port impresses more is because Duke3d-like renderers can work on straight spans and only interpolate textures in on direction and also get "free" hidden-surface culling (ie they never draw more than is seen), Tomb Raider on the other hand seems to have arbitrary texturing probably more overlap as well.