The desktop version of Codex has pets — little pixel characters rendered on top of the UI that show what the agent is currently doing. When it's working, the pet walks around; when it's waiting for input, it calls for you; when something goes wrong, it squints, and so on. The general idea is that you kick off some workflow, go do something else, and can still tell at a glance how things are going.

Not exactly a killer feature, but it's fun. I wasn’t particularly into the built-in pets, though, so I started browsing community-made ones and somehow ended up making my own — based on Hatsune Miku's design from Miku'n POP, an ancient little platformer.

Turns out it's not especially complicated. I took the sprites from MikuPet, whose author uses the same Miku'n POP design. The pet format itself is pretty straightforward, and with Codex helping me poke around, there wasn't much reverse-engineering involved. I actually spent more time figuring out who owns which bits of artwork, what the reuse terms are, and all that fun licensing stuff.

You can grab the pet from GitHub. There’s also a screenshot and a detailed rundown of what's under the hood.

Free bonus: the release workflow for a project like this can, with complete justification, be called "Release pet" :)