Single player, by 
Administrative notes: I don’t know why this level is listed as TSF+; I played it in 1.23+ just fine. Also you need to include the tileset (Desolation7th.j2t) or a lot of people won’t be able to play it.
That aside, this is pretty cool. With all the power that JJ2+‘s angelscript implementation offers, Survival Mission 1 is a good reminder that you don’t need to use every single function and rewrite every last bit of JJ2 and pretend you’re writing an entirely new game just to make a playable level. SM1 uses angelscript to take certain actions just a little farther than they could be done in JCS alone—cutscene-like dialogues, flashing lights, announcements—without creating the impression it’s anything other than a JJ2 single player level. It’s very subtle, and we could definitely use more levels like it in that respect.
(Also there’s mouse aiming and several of the enemies have higher hit counts, but besides that it would be very easy not to realize the level is scripted at all, if you’re a casual player who isn’t incredibly familiar with every single thing JCS can or cannot accomplish.)
Of course, once scripting is involved at all it’s easy to think of places that could have been a bit more elaborate. At least one point in the level would feel more complete with an accompanying music change. And I found myself getting lost a whole lot while playing; text alerts would announce that some door had been opened but woudn’t tell me where that door was, and those would have been excellent use cases for moving the player’s camera to focus on the newly opened door for a few seconds. And some more lighting effects would have been nice.
Anyway, how’s the level? It’s all right. It’s a classic sort of level where there are various places with labels like “generator” or “engine room”, and you have to find various trigger crates/zones to progress. Some enemies are supposed to be guarding various rooms, as indicated by their sitting in giant chairs or stuff like that. You shut down a “core” and then find your way out again. We’ve seen this exact theme in Another Story, and maybe other levels even older than that, but that’s not necessarily a bad thing.
I have to say, though, the layout was too cramped for my tastes. It definitely made the mouse aiming feel incredibly useful at times, particularly when I was climbing up a tower and shooting the enemies walking around on the ledges above me, but it also meant that the seekers and RFs didn’t have very much to do. (And there wasn’t a lot of ammo at all, especially in a level where half the enemies had higher-than-usual hit counts.) And the level was also quite compact, forcing a lot of paths to be right above or below one another even if they weren’t necessarily close to each other in terms of semi-linear layout. This made things more confusing than they needed to be, and also reduced the possibility of making different areas of the map visually distinct from one another.
So there are definitely various improvements that the author can make here, but it’s a pretty playable experience provided you don’t get too lost. I think the level of scripting is just fine, and the visuals are plain but serviceable, so I’d suggest concentrating primarily on design in the immediate future. Don’t be afraid to make things bigger. Work on getting the layout to match the theme. Find ways of indicating what path needs to be followed. Compare the ammo you offer to the places they can be used.
Download recommended? Sure. It’s not spectacular, but it’s a solid foundation. For players, there are some decently attractive areas and reasonable challenges—float suckers put in several appearances in their classic role as buttstomp targets—and you’ll get a chance to kill some enemies and stomp some crates, so long as you don’t get too confused about where to go next. For level makers, it’s a reminder that the barrier of entry to angelscript is only as high as you want it to be, and you can make a level that only needs it for one specific purpose instead of worrying about the whole level being a backseat to showing off your scripting skills. It’s a traditional JJ2 SP experience with some mouse aim thrown into the mix, so if you’re into that sort of thing—and, well, you are on J2O—have at it?