That's a cool tech demo. Also amazing is the soundtrack, especially considering the sound capabilities of the ZX Spectrum 😳

Guys, the Doom game is made on/for a ZX Spectrum clone (a Russian one if I am not mistaken), so in some ways they are some times more powerful, and not always 100 % compatible with the original hardware.
Not that I do not it is an awesome feat, since I think it is. But some years ago I took a dive/look into the "clones" of the ZX Spectrum, and I was amazed about how awesome they were. Also the sound department was what tipped me off, since I seem to remember one of the clones had better sound, if not an actual sound card. So take a look into it, and you will be amazed just like me 😀 also you can take a look at the Prince Of Persia game. Okay, enough bollocking around, I love clones(of many machines). So that is why I had a suspicion about it.

Actually, there are THREE demos called "Doom" (none of them is a complete game).

- Doom (by Cobra Soft): Playable? on 48k and 128k machines, distributed as a tap file or a trd disk image (the later only suitable for Scorpion, Pentagon and other clones that support TR-DOS).
- Doom (by Digital Reality): Playable only on 128k machines, distributed as a tap file or trd disk image.
-Doom 2: Seems to be an April's fool day joke.

Keep in mind that speccys are not very suitable for those things, and these demos are not intended for use as a game.