Anatomy skill

---
name: anatomy
description: Build crafted, highly detailed, interactive isometric SVG figures that explain a technical idea as a real physical object (a test rig, a dial gauge, a cabinet of drawers, a plotter, a lock), with many small precise solid parts, four-tone shading, correct painter's order, a framed card with title, hint and live readout, and calm eased motion. Use this whenever someone wants an isometric illustration, an explanatory diagram or figure for docs, a blog post, a landing page or an article, a "Linear-style" or "premium" technical drawing, an interactive explainer, or an SVG that shows how a system, algorithm or component works, even if they never say "isometric". Works framework-free (TypeScript/JS that writes SVG and HTML) and in React/Next.js, and can add realistic WebGL shaders (fire, exhaust, water, caustics, lamp light) that live inside the drawing in the same isometric perspective. Also publishes a finished figure to the Anatomy community gallery when asked.
license: MIT
compatibility: Written for Claude Code; also runs in Antigravity, OpenCode, Codex and MiniMax Code. Needs Node.js 20.10+, and Chrome or Chromium for the checks.
metadata:
  opencode/slash: "true"
---

# Anatomy

This skill makes figures like a small instrument on a bench: a heavy base on feet, rails with tick rulers, a carriage on bushings, knurled knobs, coil springs, a dial gauge whose needle moves, screws as tiny dots. The reader understands the idea because they recognise the machine. Every number the figure shows comes from the same model that moves its parts.

Eight complete examples ship with the skill. Open the closest one before you start. Each framework-free example is built with `node examples/<name>/build.mjs`, which writes a standalone HTML page next to the script; add `--light` for the light theme.

- `examples/dial-indicator/` is the smallest: a dial gauge on a stand, about 300 lines in all.
- `examples/desk-computer/` is framework-free SVG: a desk computer with a keyboard you can type on. The typed line appears on a CRT screen drawn in the plane of the case front, and the picture collapses to a line and a dot when you switch it off. It has about 85 solids and 850 paths.
- `examples/arcade-cabinet/` is an upright arcade cabinet with its side panel off, a Hero of about 240 solids and 15 cables. A quarter flies into the slot, rolls down the coin chute at the speed a rolling disc reaches on a 30° slope, trips the coin-switch wire and drops into the cash box; the switch's pulse runs chunk by chunk along its cable to the board, and the CRT warms up, self-tests and runs an attract mode drawn in the plane of the tilted monitor. The stick tilts and closes a microswitch under the panel. It shows how to place a camera so a cutaway's mechanism stays in view, a concave board drawn as a prism along any axis, moving parts rebuilt in the page from the same module the build uses, and live coins and a wire drawn in reserved slots of the settled order. `node build.mjs --audit` proves the geometry.
- `examples/raptor-engine/` is a rocket engine hanging in a test stand. Its round parts come from `kit/lathe.mjs` and its pipes and harness from `kit/tube.mjs`. It comes apart into 11 assemblies with staggered springs and per-frame depth re-sorting. Every part records its true shape, and `node build.mjs --audit` (`kit/audit.mjs`) proves, at rest, apart and in every replayed frame of the explode, that nothing passes through anything, that every end sits on a real mount, that no bend pinches, folds or lands on another line, that no curved profile's slope wobbles, and that every overlap is drawn in depth order. A WebGL plume, shock, splash and steam render between the back and front SVG. It is the reference for dense pipework, smooth shading and fades.
- `examples/ripple-tank/` is a school ripple tank on tall legs over a paper screen, seen from 44° up. Two WebGL layers (lamp light, shadows and caustics on the paper, and the water's reflections and glass) are registered to the isometric planes and driven by a pure dispersion and optics model (`model.mjs`); a frequency change travels out from the dippers through a history texture.
- `examples/test-rig/` is a production figure from a real site (React/Next): a glass button on a spring-mounted carriage, a finger probe on a rail that presses and pulls, and a dial gauge reading the lean. It has 53 solids and about 470 paths.
- `examples/spot-plate/` is a second production figure from the same site: six pairs of glass drops on a spot plate, each pair drawn from one distance field, so a pair closer than `merge` runs together into one piece of glass. A fan of feeler blades sets `merge`, one blade per gap. It is the reference for shapes that morph into each other and for one control driving many parts.
- `examples/turning-dial/` is the optional 3D mode: a combination dial that turns in true 3D with a small robot hand on it. It has about 90 live parts in metal materials, a second turn group, a hinge, a three-hinge finger that lifts and a pod that breaks off as a free body. A WebGL LED, its light pool and sparks follow the moving parts. `stress.mjs` beside it is a dense hand of about 380 parts in a cluttered workshop, used to measure performance.

The test rig is the quality bar for the drawing itself. The Raptor is the bar for shader work: a WebGL effect has to reach its standard of world-space, no-pop, seamless rendering.

## The one idea that matters

**The object is the explanation.** Don't draw boxes, arrows and labels. Invent a real, well-made physical thing whose working *is* the concept. Here is how earlier figures mapped: