Decided to dig out an old gradient shader from another LD entry, (LD31: Entire Game on One Screen) and of course realized it was off in its rendered size.
So I rewrote it. And while doing so I ended up trying some other things that I found during the research.

And suddenly ~5 hours have passed, and I've made something beautiful with no actual gameplay...

And an animated version is available too, since it still looks much better in motion, even after imgur's had a go at it.