cc-mod-ferro

<img src="preview/ball-sit.svg" width="100%" alt="Ferro, a pixel-art Norwich Terrier, chasing an orange ball across a scrolling meadow, then sitting down to look at you">

A Claude Code mod for the Code tab of Claude Desktop. When Claude works on a turn for longer than 20 seconds, a band opens above the prompt and Ferro, a Norwich Terrier, runs across a pixel-art meadow. When the turn ends, the band disappears. Nothing is interactive, so there is nothing to miss when you are not looking.

What Ferro does

Every turn picks a meadow, what Ferro does 16 seconds into the run, and whether she chases a ball, all at random. The scenes below loop the same way the band does, so each one shows its moment 16 seconds in.

Sits down and looks at you (60% of the turns). She brakes, sits, turns her head to you, blinks, tilts her head, turns back and runs on.

<img src="preview/sit.svg" width="100%" alt="Ferro sits down on the meadow and looks at you">

Poops while walking (30% of the turns), the way the real Ferro does: hunched, walking slowly forward, leaving a row of droppings that scrolls away with the grass.

<img src="preview/run.svg" width="100%" alt="Ferro poops while walking across the meadow">

Poops in one spot (10% of the turns), the rare way.

<img src="preview/autumn-run-still.svg" width="100%" alt="Ferro stops and poops in one spot on the autumn meadow">

Chases an orange ball (a third of the turns, on top of the above). The ball bounces ahead of her; when she stops, it rolls on and waits on the grass until she reaches it, then pops up again.

<img src="preview/autumn-ball-run.svg" width="100%" alt="Ferro chases an orange ball across the autumn meadow">

Falls asleep after 3 minutes. She lies down and breathes, and z's rise above her head.

<img src="preview/autumn-sleep.svg" width="100%" alt="Ferro asleep on the autumn meadow">

The meadow is summer or autumn, in three layers (clouds, hills with trees, grass) that scroll at different speeds. A winter meadow is built but switched off for now.

<img src="preview/winter-sit.svg" width="100%" alt="Ferro sits down on the winter meadow">

How it is built

Art. ChatGPT drew the frames (run, poop, sleep and sit as 6-frame strips, the hunched walk as a 4-frame strip with three droppings, all on a magenta background) and the three meadows. tools/build.py turns them into real pixel art: it cuts the frames, removes the magenta, snaps them to a true pixel grid, maps every pixel to a frozen 22-colour palette (assets/palette.json, plus reserved colours for the tongue and the eye highlight), cleans the outline, keeps one highlight in each eye and aligns the frames on the ground line and on the ear, or on the front paws where the head turns. ChatGPT drew some strips at a different scale than asked, so each strip has its own factor that gives Ferro the same head size everywhere. The sleeping breath and the blink while she sits are derived in code from one frame, so the pose never jumps. The orange ball is drawn in code. Each meadow is split into its three layers, and the clouds get their own small palette so their light-blue shading survives. Colours the meadow palette misses by far get extra slots, which keeps the brown trunks of the winter trees brown.

<img src="assets/ref/ferro-ref.png" width="100%" alt="Reference sheet for ChatGPT: Ferro standing, running and facing the viewer, the palette and every frame of every animation">

The reference sheet above goes into every ChatGPT request for new frames, so new drawings keep the same Ferro. The instructions and the prompts that produced each strip are in assets/ref/chatgpt-project.md.

Rendering. The Desktop band can draw an Svg element, but it does not render <image> with PNG data, so every frame is converted to vector strokes: one <path> per colour, one stroke per horizontal run of pixels, defined once in <defs> and placed with <use>. All animation is SMIL inside the SVG, so the mod draws the scene once and the browser engine animates it. tools/scene.py builds the three running scenes and the sleeping scene for each meadow into plugin/hooks/scene.ts and preview/.

Constraints that shaped it.

• The Svg element accepts at most 131,072 characters. On the summer and autumn meadows the running scenes are about 118k (pooping while walking), 114k (sitting) and 110k (pooping in one spot), and the sleeping scene about 85k; the ball adds about 6k, and the more detailed winter meadow about 7k. That is why sitting is a scene of its own instead of an extra moment in a running scene.
• The ball is a separate piece of SVG the mod inserts into the plain scene, so no scene is stored twice.
• The loop is seamless: in one loop the ground travels exactly 20 meadow widths and the hills, at 0.35 of the ground speed, exactly 7.
• ChatGPT returned the gallop frames out of phase order, which made Ferro look like she was running backwards. The real order is [4, 3, 2, 5, 0].

The mod. plugin/hooks/register.tsx starts two timers on turn.start (20 s to run, 3 min to sleep) and picks the turn's meadow, running scene (60-30-10) and ball (one in three), keeping all of it in $.state. The timers are cleared on the main turn's turn.complete. The band is drawn with a ui.render hook on AbovePrompt, only on the desktop surface.

Install

claude plugin marketplace add <path-to-this-repo>
claude plugin install cc-mod-ferro@cc-mod-ferro --scope user

Function hooks of installed plugins may need "CLAUDE_CODE_ENABLE_FUNCTION_HOOKS": "1" in the env block of ~/.claude/settings.json. It works only in the Code tab of Claude Desktop, because the terminal has no Svg element.

Check and test: claude plugin validate ./plugin and claude plugin test ./plugin.