3D in QBasic - Because you can! Running on my old Chicony NB 5620 brick laptop with a pathetic 4 FPS. The routines would use floating point for calculations while this laptop has no floating point coprocessor installed. On a 25MHz 4.86 with a VLB video card it could achieve full frame rate. The 3D area was meant to be "widescreen" on 640x350 which was made even narrower by the laptop's LCD.
The program was created some time back in 2004 or even earlier, probably on that above-mentioned 4.86 I had back then.