GitHub Repo Tour — Scrolling Video with Synced Narration & Subtitles

Depends on: website-to-hyperframes — load it before starting. Its 6-step workflow and reference files apply here. This skill specializes that workflow for single-page scrolling tours with narration and visible subtitles.

What This Skill Produces

A 1080x1920 portrait video (Instagram Reels format) that:

1. Shows a GitHub repository page — full-page mobile screenshot, scrolling smoothly from top to bottom over 15–30 seconds.
2. Narrates the tour — ElevenLabs AI voice describing what's on screen, synced to the scroll position.
3. Burns subtitles on screen — word-by-word caption overlay that highlights each word as the narrator speaks it. The viewer reads along while listening.
4. Ends with a CTA — "Star on GitHub" or "Follow for more" call to action.

Core Decisions

Directory Structure

github-promos/
  <repo>-tour/
    index.html              ← main HyperFrames composition
    package.json            ← from hyperframes init
    hyperframes.config.json ← HyperFrames config
    SCRIPT.md               ← narration script with timestamps
    assets/
      repo-page.png         ← Full-page GitHub screenshot (dark mode, mobile viewport)
      narration.mp3         ← ElevenLabs voiceover
    renders/                ← generated MP4s

Workflow

Step 0: Capture Repo Info & Screenshot

Use web-search or fetch_url to get repo metadata:

• Stars, forks, watchers, open issues
• Primary language, description, topics
• README summary (what the project does, key features)

Then use the screenshot skill to capture a full-page, dark-mode, mobile-viewport screenshot:

use_skill("screenshot")
// URL: https://github.com/{owner}/{repo}
// Full page, dark mode
// Viewport: 390px wide (iPhone 14 mobile) — the screenshot should
//   capture the full height of the page at mobile width
// Save as: github-promos/<repo>-tour/assets/repo-page.png

Get the screenshot dimensions (you need the pixel height for scroll math):

sips -g pixelHeight github-promos/<repo>-tour/assets/repo-page.png
sips -g pixelWidth github-promos/<repo>-tour/assets/repo-page.png

Step 1: Write the Narration Script

Write a 15–30 second script that describes what the viewer sees as the scroll progresses. The narrator walks the viewer through the page:

[0s–4s]  "This is {repo}. {one-liner description}."
[4s–8s]  "Here's the README — installation is one command."
[8s–13s] "Scrolling through the feature list — {mention 2-3 visible features}."
[13s–18s] "{stars} stars, {forks} forks, and a growing community."
[18s–23s] "Star it on GitHub. Link in bio."
[23s–25s] "Follow for more."

Rules for the script:

• The narrator references what's currently on screen at each scroll position.
• Total word count: 50–75 words (comfortable pace for 15–30 seconds).
• No filler ("um", "uh", "let me show you"). Every word earns its place.
• End with a clear CTA.

Step 2: Generate Voiceover via ElevenLabs

curl -s -X POST "https://api.elevenlabs.io/v1/text-to-speech/AZnzlk1XvdvUeBnXmlld" \
  -H "xi-api-key: $ELEVENLABS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "text": "FULL_SCRIPT_HERE",
    "model_id": "eleven_multilingual_v2",
    "voice_settings": {
      "stability": 0.35,
      "similarity_boost": 0.8,
      "style": 0.25,
      "use_speaker_boost": true
    }
  }' \
  --output github-promos/<repo>-tour/assets/narration.mp3

Verify the file exists and has size > 0.

Step 3: Transcribe & Time-Map

After generating audio, extract word-level timestamps:

Option A: ElevenLabs timestamps (returned with the API response if output_format: "mp3" is not the only output — check the API docs for aligned output).

Option B: Use ffmpeg + Whisper (local transcription with word timestamps):

# Install whisper if needed
pip install openai-whisper

# Transcribe with word timestamps
whisper github-promos/<repo>-tour/assets/narration.mp3 \
  --model base \
  --output_format json \
  --output_dir github-promos/<repo>-tour/assets/ \
  --word_timestamps True

The output gives you words[] with start and end timestamps for each word. Map these timestamps to the scroll positions.

Step 4: Build the HyperFrames Composition

Create index.html following the HyperFrames composition architecture:

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8"/>
<meta name="viewport" content="width=1080,height=1920"/>
<script src="https://cdn.jsdelivr.net/npm/gsap@3.12.5/dist/gsap.min.js"></script>
<link href="https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700;800;900&display=swap" rel="stylesheet">
<style>
  /* ── Root & Canvas ── */
  * { margin: 0; padding: 0; box-sizing: border-box; }
  #root {
    position: relative;
    width: 1080px;
    height: 1920px;
    background: #0d1117;
    font-family: 'Inter', sans-serif;
    overflow: hidden;
  }

  /* ── Scrolling Screenshot ── */
  .scroll-container {
    position: absolute;
    inset: 0;
    width: 1080px;
    height: 1920px;
    overflow: hidden;
  }
  .scroll-content {
    position: absolute;
    top: 0;
    left: 0;
    width: 1080px;
    height: VAR_IMG_H px;   /* actual screenshot height */
  }

  /* ── Subtitle Overlay ── */
  .subtitle-bar {
    position: absolute;
    bottom: 180px;
    left: 50%;
    transform: translateX(-50%);
    width: 1000px;
    text-align: center;
    z-index: 100;
  }
  .subtitle-word {
    display: inline-block;
    font-size: 42px;
    font-weight: 700;
    color: rgba(255,255,255,0.35);
    padding: 0 4px;
    transition: color 0.08s, transform 0.08s;
  }
  .subtitle-word.active {
    color: #FFFFFF;
    transform: scale(1.08);
  }
  .subtitle-word.past {
    color: rgba(255,255,255,0.65);
  }

  /* ── Scroll Progress Bar ── */
  .scroll-progress-track {
    position: absolute;
    right: 16px;
    top: 100px;
    width: 5px;
    height: 1720px;
    border-radius: 3px;
    background: rgba(255,255,255,0.1);
    z-index: 50;
  }
  .scroll-progress-thumb {
    position: absolute;
    top: 0;
    left: 0;
    width: 5px;
    height: VAR_THUMB_H px;
    border-radius: 3px;
    background: linear-gradient(180deg, #58a6ff, #3fb950);
    z-index: 51;
  }

  /* ── CTA Overlay (Beat 6-7) ── */
  .cta-overlay {
    position: absolute;
    inset: 0;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    background: rgba(13,17,23,0.92);
    backdrop-filter: blur(8px);
    z-index: 200;
    opacity: 0;
  }
  .cta-title {
    font-size: 56px;
    font-weight: 800;
    color: #e6edf3;
    text-align: center;
  }
  .cta-subtitle {
    font-size: 32px;
    color: #8b949e;
    margin-top: 16px;
  }
  .cta-button {
    margin-top: 40px;
    padding: 18px 48px;
    background: #238636;
    color: #e6edf3;
    font-size: 28px;
    font-weight: 700;
    border-radius: 999px;
    box-shadow: 0 0 30px rgba(35,134,54,0.5);
  }
  .follow-pill {
    margin-top: 24px;
    padding: 12px 28px;
    background: rgba(22,27,34,0.8);
    border: 1px solid #30363d;
    border-radius: 999px;
    font-size: 22px;
    color: #e6edf3;
    font-weight: 600;
  }
</style>
</head>
<body>
<div id="root"
  data-composition-id="{repo}-tour"
  data-width="1080"
  data-height="1920"
  data-start="0"
  data-duration="{total_seconds}">

  <audio id="narration-audio"
    src="assets/narration.mp3"
    data-start="0"
    data-duration="{total_seconds}"
    preload="auto"></audio>

  <!-- Scrolling screenshot (full-canvas) -->
  <div class="scroll-container">
    <img class="scroll-content" src="assets/repo-page.png" />
  </div>

  <!-- Scroll progress bar -->
  <div class="scroll-progress-track">
    <div class="scroll-progress-thumb" id="scroll-thumb"></div>
  </div>

  <!-- Subtitle overlay -->
  <div class="subtitle-bar" id="subtitle-bar">
    <!-- Words injected by JS, one <span class="subtitle-word"> per word -->
  </div>

  <!-- CTA overlay (final 5s) -->
  <div class="cta-overlay" id="cta-overlay">
    <div class="cta-title">Star on GitHub</div>
    <div class="cta-subtitle">{repo description}</div>
    <div class="cta-button">github.com/{owner}/{repo}</div>
    <div class="follow-pill">@githubprojects</div>
  </div>
</div>

<script>
// ── Scroll Math ──────────────────────────────────────────
var IMG_H = /* actual screenshot height */;
var CANVAS_H = 1920;
var MAX_SCROLL = IMG_H - CANVAS_H;
var THUMB_TRACK = 1720;
var THUMB_H = Math.round(THUMB_TRACK * (CANVAS_H / IMG_H));
var THUMB_TRAVEL = THUMB_TRACK - THUMB_H;

function thumbTop(scrollY) {
  return (Math.abs(scrollY) / MAX_SCROLL) * THUMB_TRAVEL;
}

// ── Word Timestamps ─────────────────────────────────────
// Paste the word-level timestamps from Step 3 here.
// Format: [word, startSeconds, endSeconds]
var WORDS = [
  // ["This", 0.0, 0.3],
  // ["is", 0.3, 0.5],
  // ["mercury-skills", 0.5, 1.0],
  // ...
];

var TOTAL_DURATION = /* total seconds from audio */;

// ── Build Subtitle Spans ────────────────────────────────
var subtitleBar = document.getElementById("subtitle-bar");
var wordSpans = [];
WORDS.forEach(function(w, i) {
  var span = document.createElement("span");
  span.className = "subtitle-word";
  span.textContent = w[0];
  subtitleBar.appendChild(span);
  wordSpans.push(span);
});

// ── GSAP Timeline ───────────────────────────────────────
window.__timelines = window.__timelines || {};
var tl = gsap.timeline({paused: true});

// Phase 1: Scroll (0s to ~80% of total duration)
var scrollEnd = TOTAL_DURATION * 0.80;
var ctaStart = TOTAL_DURATION * 0.80;

// Scroll from top to bottom with easing
tl.to(".scroll-content", {
  y: -MAX_SCROLL,
  duration: scrollEnd,
  ease: "none",
  onUpdate: function() {
    var progress = this.progress();
    var thumbTop = progress * THUMB_TRAVEL;
    gsap.set("#scroll-thumb", { top: thumbTop });
  }
}, 0);

// Phase 2: Word-by-word subtitle highlighting
var currentWordIndex = -1;
WORDS.forEach(function(w, i) {
  tl.call(function() {
    // Deactivate previous word
    if (currentWordIndex >= 0 && wordSpans[currentWordIndex]) {
      wordSpans[currentWordIndex].classList.remove("active");
      wordSpans[currentWordIndex].classList.add("past");
    }
    // Activate current word
    wordSpans[i].classList.add("active");
    currentWordIndex = i;
  }, null, w[1]);
});

// Phase 3: CTA overlay fades in at 80%
tl.to("#cta-overlay", { opacity: 1, duration: 0.5, ease: "power2.out" }, ctaStart);

// Phase 4: Dim subtitle bar during CTA
tl.to("#subtitle-bar", { opacity: 0.3, duration: 0.5 }, ctaStart);

// Phase 5: Scroll progress bar fades out
tl.to(".scroll-progress-track", { opacity: 0, duration: 0.3 }, ctaStart);

window.__timelines["{repo}-tour"] = tl;
</script>
</body>
</html>

Step 5: Render

cd github-promos/<repo>-tour

# If no HyperFrames project config exists:
npx hyperframes init --example blank --non-interactive

# Lint
npx hyperframes lint

# Snapshot to verify visually
npx hyperframes snapshot

# Draft render
npx hyperframes render --quality draft

# Verify the output MP4 in renders/
ls -la renders/

# If everything looks good, render final
npx hyperframes render --quality standard

Step 6: Deliver

Send the final MP4 to the user. Ask if they want:

• High-quality render (--quality high)
• Different aspect ratio (landscape 1920x1080)
• Script revisions

Subtitle System — How It Works

The subtitle system is the core differentiator of this skill. Here's how word-by-word sync works:

Word-Level Timestamps

The narration audio is transcribed with word-level timestamps (from ElevenLabs or Whisper). Each word gets a [word, startSeconds, endSeconds] entry in the WORDS array.

Three Visual States

Every word in the subtitle bar has three CSS states:

The GSAP timeline calls a function at each word's startSeconds to transition currentWord → active and previousWord → past. This creates a Karaoke-style word-by-word highlight that's perfectly synced to the audio.

Typography

• Font: Inter 700, 42px
• Position: Bottom 180px, centered, 1000px wide max
• Background: No background box — words float over the scroll content with the dim/bright/dim gradient making them readable against any content
• Z-index: 100 (above scroll content at z-index 1, below CTA overlay at z-index 200)

Layout Considerations

Words are laid out with display: inline-block and natural text wrapping. For longer scripts (20+ seconds), consider splitting into 2–3 line groups that appear/disappear between scroll segments:

// Group words by scroll segment
var SEGMENTS = [
  { start: 0, end: 5, words: [0, 12] },     // Beat 1: Hero
  { start: 5, end: 15, words: [13, 35] },   // Beat 2: Scroll
  { start: 15, end: 20, words: [36, 50] },   // Beat 3: Stats
  { start: 20, end: 25, words: [51, 65] },   // Beat 4: CTA
  { start: 25, end: 28, words: [66, 72] },   // Beat 5: Follow
];

Each segment fades in its words and fades out the previous segment's words, preventing subtitle overload during long scrolls.

Scroll Mechanics

Full-Screen Mobile Viewport

The GitHub screenshot fills the entire 1080x1920 canvas — no phone bezel, no sidebar, no letterboxing. The viewer sees the repo page exactly as it appears on a mobile phone in dark mode.

Smooth Continuous Scroll

The scroll is a single gsap.to() animation from y: 0 to y: -MAX_SCROLL over the first 80% of the video duration. This means:

• A 25-second video scrolls for 20 seconds, then shows the CTA for 5 seconds.
• A 15-second video scrolls for 12 seconds, then shows the CTA for 3 seconds.

The easing is "none" (linear) by default because the subtitles handle the pace perception — the narrator's word highlights create the feeling of "stopping" at interesting sections even though the scroll is continuous.

If you want variable-speed scroll (slower at interesting sections, faster at filler):

// Replace the single gsap.to with a timeline of segments:
tl.to(".scroll-content", { y: SCROLL_30PCT, duration: scrollEnd * 0.35, ease: "power2.out" }, 0);
tl.to(".scroll-content", { y: SCROLL_70PCT, duration: scrollEnd * 0.40, ease: "power1.out" }, scrollEnd * 0.35);
tl.to(".scroll-content", { y: -MAX_SCROLL, duration: scrollEnd * 0.25, ease: "power3.in" }, scrollEnd * 0.75);

Map the slow segments to the sections the narrator calls out by name.

Narration-Aware Timing (MANDATORY)

The scroll speed and CTA timing are derived FROM the narration audio, not the other way around.

1. Write the script first. Know what you're going to say.
2. Generate the audio. Get the actual MP3 file.
3. Measure total duration. ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 assets/narration.mp3
4. Transcribe with word timestamps. Get WORDS[] with start/end per word.
5. Set data-duration on #root to the measured total duration.
6. Set data-duration on <audio> to the measured total duration.
7. Set TOTAL_DURATION in JS to the measured total duration.
8. Calculate scroll/CTA splits from TOTAL_DURATION:
   • Scroll phase: 0% to 80%
   • CTA phase: 80% to 100%

Never hard-code a duration and then try to fit the narration into it. The narration decides the duration.

Color Scheme (GitHub Dark)

Variations

Landscape (1920x1080)

Change data-width="1920" data-height="1080" and adjust:

• .scroll-container to 1920x1080
• Subtitle bar to bottom: 80px, width: 1800px
• CTA overlay sizing
• Screenshot capture at desktop width (1280px viewport)

With Background Music

Add a second <audio> element with a low-volume ambient track (royalty-free). Set its data-start and data-duration to match the narration.

Multiple Repos in One Video

Create separate compositions per repo, then use npx hyperframes compose to concatenate them with transitions between.

Prerequisites

• ELEVENLABS_API_KEY environment variable
• Node.js >= 22 with HyperFrames CLI installed (npm install -g hyperframes)
• ffmpeg in PATH (for duration measurement)
• whisper installed if using local transcription (Option B in Step 3)
• screenshot skill available (for capturing the GitHub page)

Troubleshooting

Skill Dependency

Required: website-to-hyperframes — load it before starting. Its 6-step framework (capture → brand → brief → storyboard → build → validate) governs this skill's workflow. This skill specializes it for scrolling repo tours with synced subtitles on a full-screen mobile viewport.

Suggested: screenshot skill — for capturing the full-page GitHub repository screenshot in dark mode at mobile viewport width.