We wrote this game on DirectX 1.0. It was a pig because the game was designed to be all 2D sprites, but early in the project it became clear there wasn't enough RAM, so I wrote a 3D engine that integrated with the 2D backgrounds. The video cards of the day didn't like that shit, and there was no acceleration at the time.

https://www.youtube.com/watch?v=9UOYps_3eM0

All the DirectX code itself felt sluggish as games were coming from highly optimized bare-metal C/x86 to running on a multi-tasking OS through an API that was written in (probably) pretty unoptimized C++.