Very solid submission. It might not quite make my top five of the jam but it's definitely in the top ten.
I think this would only get four stars for Theme if not for the visual treatment, but I gave you a bump to the full five because I love that you went full on cute water park with the design and stuck with it even as you're describing little kids exploding in showers of blood. That, to me, emphasizes without directly saying to the Warden that they've got to play up the wholesomeness of everything in the early stages, before the gore starts, which is where it really becomes "beneath the surface."
There's potential for some great surreal dark humor here as the grizzled space marines, empty-eyed androids and neurotic scientists feel completely out of place at first in this happy, cutesy environment, before going "oh okay that's more our vibe" as the chest-bursting aliens show up.
I also think this is really easy to run as a one-shot. I feel like with my groups and my style of Wardening, most one-shots actually require two sessions to get through. But this feels easily doable in a single session, and you've made it simple to just pick up and go.
I've complained about the too-casual tone of writing in some other modules, but this is an illustration of how to make it work. It's thoughtfully casual, not off-the-cuff. Where you're using shorthand and glossing over things, I can tell you're thinking about the end reader, not just writing for your own benefit. It's easy to follow your train of thought because you're not skipping over anything that can't easily be inferred, and keeping all the information in a logical order. The informal tone also serves a specific purpose here in that it matches the visual presentation.
If I have to criticize something, the layout is a little sloppy here and there. It looks okay at a glance, but for those attuned to such things, you can tell it was a little rushed. I'd explore some other options for the body font, for instance. And the there are inconsistencies in terms of things like spacing between the headers and the text underneath them. Tuning up those kinds of things are what would take this from "very good jam entry" to "professional finished product."