---
name: twin-sliders
description: Create an editable comparison film with two numeric scales, synchronized indicators, and linked context symbols.
version: 1.0.5
category: video
delivery: download-only
---

# Twin Sliders

Turn a two-axis comparison into a 1920 × 1080 film. This is a parameterized HTML/SVG renderer with a GSAP timeline and HyperFrames export. It accepts structured content; turning a prose request into suitable scores and captions requires authoring.

Read `references/authoring.md` for the input contract. Build a brief with a heading, two named gauges, explicit endpoints and 2–4 context options. Use justified measurements or disclose illustrative scoring. Each option names the gauge it explains.

Run with Node.js 20+:

```
node scripts/create.mjs --brief /absolute/brief.json --dest /absolute/new-project
node scripts/render.mjs /absolute/new-project
```

FFmpeg and HyperFrames 0.8.30 are required for export. The render command obtains the pinned CLI with npx; internet is required on first installation. Set HYPERFRAMES_CLI to an installed 0.8.30 CLI file for offline rendering. GSAP and the CJK-capable Noto Sans SC font are bundled with their notices in assets/vendor/. No model calls, keys or paid generation are needed.

The output project includes editable index.html, brief.json, audio-timeline.json and local dependencies. Edit the brief and generate a fresh directory to rebuild. Project creation refuses to overwrite existing work. Open the HTML through a local HTTP server to inspect it; the timeline starts paused for deterministic export. In the browser console use `twinSeek(4)` or `window.__timelines['twin-sliders'].play(0)`.

The two tracks appear before the handles move. Each fill endpoint and handle share a computed destination. The reading and caption appear after that handle stops. Connectors draw from the actual selected positions to the option symbols, followed by a final reading hold. Boundary values 0 and 1 are supported. Choose canal, plum, fern or mineral; all use the same geometry and timeline.

Inspect both movements and their joins, verify normalized positions, check long labels at native resolution, and seek backward as well as forward. Use ffprobe and full video decoding after export. Sound is optional: generated projects are silent and contain an empty editable audio timeline. To add sound, author licensed tracks and mix them into the final export; the supplied renderer does not synthesize or mix audio. No user acceptance or aesthetic quality is implied by successful rendering.