This is cool. I like this. I'm not familiar with the 24XX system but I gave it a download and I'll skim it later. It's a shame this demo only has the intro page and the one encounter, but it does the job. I like how the information is laid out and the color-coding makes it very easy to parse, especially for solo-play. I think keeping it to single page encounters will make it easier to run as long as the information's all there. This seems easy to translate into another more familiar system and the emphasis on solo play fits well if you're planning on making these a series of 'zines. The art is a bit mix and match but that also works for the 'zine aesthetic and it's good that these different artists get to have their work included. I will say, mostly jokingly, that those detectives have the wrinkliest outfits I think I've ever seen. They might want to invest in some dryer sheets.
I think you could add a little bit more to the encounter, like relative DCs for each of the options. Maybe something like: intimidate - easy, with advantage if the players brandish at least 2 pistols or 1 bigger gun. Deceive - easy. Persuade to leave peacefully - hard. Crack safe - easy with skill. Break open safe - medium. Speaking of, is 2 credits a lot of money in this world or is that as pathetic as it sounds? You could also add some more items to the scene to give it a bit more character, and then maybe have a glossary at the back to reveal what's actually useful. Something like: key from vic's apartment - used to bypass a locked door in scene 6. Hula girl lamp - useless.
I did notice a possible problem with designing the game around solo play first and then translating it to multiplayer. Zephyr's character bio states she and the investigator used to be a thing. What, like all of them at the same time?
"Of all the detectives to walk into my shop, it just had to be the 4 I was in an unstable polycule with."
"We weren't aware it was a polycule, Zeph. From our perspective it was just cheating."
"Yeah, well... ain't perspective a beautiful thing?"
It might be better to make that sort of backstory optional, so the players won't have character traits decided for them. And then choosing a backstory element could give advantage or disadvantage to various checks to deepen the gameplay and make the storytelling more interesting.
This shows promise. I might actually use this as an outline for designing my own solo modules if I ever do that, so thanks for that. Good stuff.