UKKO is a browser-based game engine where the body is the controller. The player stands in front of a webcam; a Python MediaPipe + RTMO worker watches their pose in real time; a Go gateway routes detected gestures back to a SvelteKit frontend that responds by sequencing video clips. No 3D rendering, no controllers, no app — a game is a content pack of clips, transitions, and pose-trigger rules.

The "games are content, not code" thesis

Most game engines ship a runtime and a level editor; UKKO flips that — the runtime is the engine plus a clip library plus a small DSL of pose-to-clip rules. New experiences don't ship new builds; they ship a new pack. The bet is that for the target use case (event installs, museum kiosks, brand activations) the bottleneck is rarely "we need a custom engine," it's "we need this whole thing to ship by Friday with different art." UKKO is the version of that loop that lets non-engineers iterate on the experience.

Architecture

• Frontend — SvelteKit 2 + Svelte 5 + Tailwind v4 + shadcn-svelte. Renders the clip player, captures webcam frames, ships them to the gateway, and responds to clip-change events. Built to run as a kiosk full-screen tab.
• Gateway — Go 1.24 with chi for HTTP routing, SQLite (WAL) under sqlc-generated query layer, goose for migrations. Stateful for sessions; a thin translator between the browser and the vision worker.
• Vision worker — Python 3.12 + FastAPI wrapping MediaPipe + RTMO models. Consumes frame batches, emits pose events; can be scaled separately from the gateway since it's the only GPU-hungry piece.
• Deploy — systemd services behind Apache with Let's Encrypt SSL on the public install. No Docker in production; the offline kit (see below) is rsync-able directly to a USB stick.

Offline-first by design

UKKO is being prepared for a fully air-gapped event deployment in May 2026. The repo carries a just offline-kit recipe that produces a single USB-portable artifact bundle: pre-built binaries, the SvelteKit static export, the Python worker with cached weights, all systemd unit files, and the sqlite migrations. The smoke-test recipe rehearses the full one-command bring-up on real hardware. The architecture rationale lives in docs/offline/feasibility-windows.md; the constraints those binding guardrails enforce live in the repo's CLAUDE.md.

Why "UKKO"

Ukko is the Finnish god of weather, sky, and thunder — a deity whose business is making things happen at scale by waving his hands. That's the metaphor. The engine doesn't care what the gesture is; it cares that the gesture happened, and that the world responds.