This is actual gameplay footage of a work-in-progress remake. It's fan-made by a group called PixelForce and they're planning on releasing it. Don't know when though. It's been Valve-approved.
I think I would've given my legs to have this game about 13-15 years ago.... Holy crap that looks like fun! I demand it be made into a real game! And it should run on the SNES emulators