All right... regardless of how unfinished it is, I have just made blue-dark the default theme for all new visitors. The option is still there, down at the bottom in the dropdown, but this one is more immediately screen-friendly regardless of size.

Uh, except the full compose window. That's definitely a step down. But I'm going to have some time coming up here, once convention stuff is done, and I hope to make some improvements including that.
A quick test also reminds me that unregistered users see a big open space instead of the funhouse chat, so I still need to throw a placeholder in there reminding them of that benefit of joining.

I think I will clone blue-dark for further development, so everyone can enjoy the mostly improved features without significant breakage as I develop. There's this amazing little idea called "literally just develop on a test version of the forum" but who knows if I'll do the sensible thing.

This is the one I'm rocking now.

Had a bit of time in cooling down after the conventions, figured there was no harm in playing around with a wee bit of styling.
Overtype is actually so freaking easy to work with. At least on the surface level - it might take some new knowledge before I'll be able to add stuff like spoilers and maybe !!nsfw tags!! but to make it look like a TB game aesthetic is surprisingly easy:

Obviously there's more tweaking to be done here to the styling, details and polishing to add, but I feel like this is a pretty good start on what could be an awesome design going forward. Eventually I'll start working this into the actual site theme.

We're making some progress here, looking more like the aesthetic I was excited for!

And look, a vaguely functional demo page!
https://inyouchuuverse.net/vn-theme-testing/css-post-test.html

Obviously the posting buttons don't work - and that's not a real thread anyway - but this might give you an idea of not only the look but the concept of the interactive editor too. There's still a lot I want to do to improve the design and add all the features (smileys, attachments, video embeds, etc) but I think it's a good start.

It's looking very good haha. Love this idea.

Oh we are absolutely making things happen now...

Starting to get kinda excited about this theme. It's not a perfect 1:1 match to the game, but it's close enough in spirit that it should be pretty clear where the inspiration came from.

And as before, a working-ish demo:
https://inyouchuuverse.net/vn-theme-testing/css-post-test3.html

Surprisingly, it seems that it is indeed shaping up to fit the name blue-dark!

Looks amazing.

Thank you! I'm starting to feel a bit more confident with CSS and theming in general at this point, so I think we've got something promising in the works here. Also, this is subtle and hard to notice, but you can sort of pick out "inyouchuuverse.net" in the middle of all the straight lines that cross through.

"I hate inefficient web sites," says hypocrite whose site theme absolutely murders performance.

Biggest issue appears to be my subtle textbox backgrounds, which are a giant SVG behind each post. I thought it was working decently well, until I noticed how bad the scrolling is when I view it on my phone. So I zoomed in on desktop and saw the same results. Hiding the image fixed it and made everything smooth.

The runes are a very subtle element of the theme anyway. It's a shame to remove that after the time I spent putting the image together, but it's not worth turning the site experience into a choppy mess for it. I could try converting to a static PNG to avoid the redraw calls, but then I'll have a much bigger chunk of data making up the site, and that too is something I find annoying.

To be honest, there are several compromises I had to make in order for that background to work in the first place, and admittedly I'm happy to not have to do that anymore. The post body div had to end exactly within the outer border, necessitating the use of some inconsistent border-image-outset parameters that I think was also causing a horizontal scroll bug I was seeing on mobile. And the slight difference in border and fill meant a hard edge that had to be mitigated with a workaround based on two instances of a box-shadow.

Ultimately I don't think that relatively small detail is a very big loss if the site works much better without it. I'll be happily sharing a new version of the example page once I put together a new header style... thinking of maybe Mikoto with sword would be a good addition to the logo.

This one?