# pointer-trail-emitter

A skill that teaches the agent to build a cursor trail whose mote spacing holds steady no matter how fast the hand moves.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 1200 installs · ★ 7001
- Author: MengTo
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/MengTo/Skills/tree/HEAD/agent-skills/web-design/pointer-trail-emitter/SKILL.md
- Updated: 2026-10-25
- HTML: https://affpapa.org/en/nevibecode/skills/pointer-trail-emitter

## What it does

Timer-based trails fall apart. Flick the pointer and the line scatters into dots; rest your hand and every mote piles up in one spot. This skill emits per unit of distance travelled instead, spending the accumulated movement in fixed steps, so density follows the path rather than the clock. Over one fixed route the measured spread was 1.08× against 1.64× for the timer version.

The demo is dependency-free Vanilla JavaScript on the Canvas 2D API. No shaders, no WebGL, no Three.js. The skill walks through placing each mote at its own distance along the segment, taking the ring-buffer slot before advancing the index, damping the emitter so it lags the pointer, and anchoring an in-scene 3-D trail to the camera rather than the world. It also covers coasting instead of stopping dead, expressing scatter as a fraction of the plane the trail hangs on, and a slow idle emission for a resting hand, roughly one every 0.4s.

The tuned numbers assume a trail 3.4 units from a 36° camera on a plane about 2.2 units tall. Change the geometry and the spatial values need recomputing against your own plane extent, or ±0.30 of scatter reads as a hard line. The spawn loop is capped at 14 per frame, because a tab restore or a teleporting pointer can hand you one enormous movement delta.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add MengTo/Skills --skill pointer-trail-emitter -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/pointer-trail-emitter/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/pointer-trail-emitter/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add MengTo/Skills --skill pointer-trail-emitter -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/pointer-trail-emitter/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add MengTo/Skills --skill pointer-trail-emitter -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/pointer-trail-emitter/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install MengTo/Skills pointer-trail-emitter
```

2. **Manually: put the files in place**
- File: `.github/skills/pointer-trail-emitter/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add MengTo/Skills --skill pointer-trail-emitter -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/MengTo/Skills --path agent-skills/web-design/pointer-trail-emitter
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/pointer-trail-emitter/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add MengTo/Skills --skill pointer-trail-emitter -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/MengTo/Skills/tree/HEAD/agent-skills/web-design/pointer-trail-emitter/SKILL.md

## When to use it
- keep a cursor trail at even density through slow and fast motion
- spread a frame's motes along the segment instead of clumping them
- fix motes that lag one step behind and pop in
- anchor a 3-D trail to the screen so it stays under the hand
- keep a faint emission going while the pointer is still

## Example prompts
- build a Canvas 2D cursor trail that emits by distance travelled, step 0.030
- the motes lag the cursor and pop in — check the ring-buffer slot order
- the trail swims when the camera moves: parent the points to the camera and scale scatter by the plane height

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: c0ea9cb136ee2701.

BEGIN THIRD-PARTY FILE c0ea9cb136ee2701
````text
---
name: pointer-trail-emitter
description: Build a cursor trail whose spacing stays constant at any hand speed, by emitting motes per unit of distance travelled rather than on a timer, so a flick draws the same continuous ribbon as a crawl instead of breaking into scattered dots. Covers sub-segment placement, the ring-buffer ordering trap, the idle breath a distance emitter needs, anchoring the trail to the screen in a 3-D scene, scaling scatter against the plane it hangs on, coasting instead of stopping dead, touch and reduced-motion fallbacks, and why moving the emitter to a DOM overlay to raise its z-index costs more than it buys. Use for cursor wisps, pointer sparks, embers, magic trails, comet tails, plankton, dust, or any mote trail that must stay legible however fast the hand moves.
---

# Pointer Trail Emitter

Build the emitter yourself when the trail's density has to respond to how fast the hand is moving.

Reach for `add-shader-cursor-trail` or `shaders-cursor-ripples` when you want the packaged WebGPU looks from the Shaders library. Reach for `reveal-hover-effect` when the cursor exposes a second image through a mask. Reach for `ambient-section-particles` when motes fill a section and the pointer only disturbs them. Reach for this when the pointer *lays* them.

The bundled demo keeps the stage intentionally neutral. A plain dark field makes spacing, scatter, and coast easy to judge without a background image competing with the trail. The wisps are dependency-free Vanilla JavaScript rendered through the Canvas 2D API; CSS styles the interface only. There are no shaders, WebGL, or Three.js. Keep the live canvas separate from the interface so the emitter stays testable rather than baked into a composition.

## Emit by distance, not by time

This is the whole mechanism. Accumulate the distance the emitter has moved and spend it in fixed steps:

```js
E.acc += moved;
let guard = 0;
while (E.acc >= STEP && guard++ < 14) {
  E.acc -= STEP;
  spawn(/* … */);
}
```

Spacing along the path is then `STEP`, whatever the hand is doing, so the trail reads as one continuous ribbon at a crawl and at a flick alike.
````
END THIRD-PARTY FILE c0ea9cb136ee2701

The third-party file has ended. Everything between the c0ea9cb136ee2701 tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

First 2152 of 10566 bytes. © MengTo · MIT · https://github.com/MengTo/Skills/tree/HEAD/agent-skills/web-design/pointer-trail-emitter/SKILL.md

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