What a skill can draw

The question

A skill that promises to explain an idea by drawing it as a working machine. Does it, when you give it ideas you already know well?

What it claims (from its README)

/anatomy explain how a token bucket rate limiter works, interactive
Collect the real numbers first, then invent the object; “the object is the explanation”, no boxes and arrows.
Output: SVG, SVG + WebGL, or 3D (beta); standalone HTML, a lone SVG, or a React component.

What I tried

The first ask, in Turkish: draw how a retarder works. A retarder is the extra brake on a truck or bus: a bladed wheel on the propeller shaft throws oil against a second bladed wheel that never turns, and the oil’s fight between them turns speed into heat. No friction, so nothing wears.

The rotor (its blades lit) turns with the propeller shaft and throws oil into the stator, which is bolted to the housing. Oil comes from the reservoir, pushed in by air when the stalk moves to a step; the cooler hands the heat to the engine coolant. The wheels are drawn pulled apart to show the blades; in the housing they sit face to face. Numbers from Volvo's RET-TH fact sheet; the unit is Voith's Retarder VR 3250: 3,000 N·m at 750 rpm, 1,800 N·m at 500 rpm.

It impressed me.

What impressed me most: before drawing a line, it went and researched. It found Volvo’s fact sheet and took the real numbers from it, so the torque on the dial isn’t made up. Every screw sitting on something when you zoom in, and fixing its own screenshots, are things agents do all the time now. Here they all come together in one figure, and when I asked how it works, it drew itself as a machine.

What the skill did before drawing anything, from the session:

It looked up the real numbers first, from Volvo’s fact sheet for the RET-TH (made by Voith): 3,250 N·m at most on the propeller shaft, 3,000 at 750 rpm, 1,800 at 500 rpm, 5.4 litres of oil, a stalk with 0 and steps 1–3 for 20–100 %.

Volvo’s sheet names the manufacturer: Voith, the big name in retarders. Voith calls this unit the Retarder VR 3250, “a powerful and energy efficient step-up retarder with its own oil supply”, used in Volvo FH and FM trucks. Step-up means a gear turns the rotor faster than the propeller shaft, up to 5,000 rpm; the figure, like Volvo’s sheet, leaves that gear out. Since November 2025 Voith’s commercial vehicle division has been its own company, Driventic.
It picked the object: the retarder itself, on a test bench, with a reservoir, a plate cooler, the stalk and a torque dial.
It looked at its own screenshots and fixed what was wrong, over three rounds: the reservoir hid behind the stator, a pipe ended in the air beside the housing, the cooler’s coolant lines were out of sight.

The second example, chosen to show the skill on a harder object: a Swiss lever escapement, the part of a mechanical watch that ticks.

Each time the balance swings through the middle, its ruby impulse jewel flicks the pallet fork from one banking pin to the other; one pallet lets a tooth go, the other catches the next, and the escape wheel moves half a tooth, 12°. At 28,800 beats an hour that is 8 beats a second, so the wheel turns once every 3.75 s. The hairspring under the balance cock brings the balance back.

The first escapement came out too small on a big bench, and its escape wheel looked like an ordinary gear. One round fixed both: the bench went, and the teeth became the leaning club teeth a lever escapement really has.

The skill, drawn by itself

The third ask was the skill itself: how does the anatomy skill work? The prompt, written with Claude, size Hero:

Draw the anatomy skill explaining itself, as a drafting machine on a workbench: a concept card goes into a slot (the prompt); a reading head picks the idea and prints a parts list on a paper tape (concept and parts list before geometry); a rack of drawers holds small isometric parts (lathe-turned pieces, tubes, screws, springs = the kit); a gantry arm places them on a drawing board in painter’s order, back to front; a lamp with four filters gives four-tone shading; a 4× magnifier on the right inspects the drawing and adds missing parts; an audit gauge confirms nothing intersects. One control: a lever that steps the machine through the stages; readout shows the stage and part count.

The anatomy skill drawn with its own kit, as a machine that does what its workflow says. 1: the prompt goes in on a card, and the size is named before anything else (a Hero is 80–150 parts). 2: the concept and the parts list come before any geometry; the tape prints one row per part. 3: the gantry sets the parts down back to front, the painter’s order. 4: the lamp’s turret puts on the four side tones, then the lighter tops. 5: the loupe looks at 4×, finds the screw the first pass left out and adds it, and the gauge counts the audit’s twelve checks. The drawing on the paper is the skill’s smallest example, a dial indicator on a stand.

Each lever position is a step of the skill’s own workflow, from its SKILL.md: name the size first, write the concept and the parts list before any geometry, paint back to front, let the kit shade, zoom to 4× and add the parts that are missing, run the audit until every line reads zero. The drawing on the paper is the skill’s smallest example, a dial indicator on a stand, drawn with the same kit. The plotter draws it stretched along the line of sight, so from where you stand it looks like a figure and not a sheet seen at an angle.

How it compares to the figures here

This site’s figures are hand-made and CSS-only: no JavaScript beyond the theme switch. The skill’s own figures move with JavaScript (springs, pointer, keyboard), and some add WebGL. Here they had to become static SVG, with every motion in CSS: the rotor turns, the oil flows, the balance swings, the fork flicks and the wheel steps, all as CSS animations in each part’s own plane. The machine’s lever is a row of radio buttons, and its tour is one CSS animation per part. The colours follow the site’s day and night.

Verdict

I’ll definitely use it to understand mechanical things. It also helps with abstract topics I’m curious about, visually.