heygen-com--hyperframes/skills/hyperframes-animation/rules/dynamic-content-sequencing.md

name, description, metadata

name	description	metadata
dynamic-content-sequencing	Auto-calculate timeline start/end times from content length + per-item duration config — longer content gets more screen time without hardcoded numbers.	tags timeline, sequencing, dynamic, duration, content-aware, utility

Dynamic Content Sequencing

A utility pattern (not a motion rule in itself) for scenes that show a SEQUENCE of items (cards, phrases, stats). Each item's duration is calculated from its content length + a per-item config; the sequencer assigns absolute start/end times automatically. Distinct from discrete-text-sequence (which is one text element changing states) — this rule swaps between distinct content blocks.

How It Works

1. Define a content array — each entry has { text, speedFactor, hold } (or arbitrary fields)
2. Pre-compute absolute start times: start[i] = sum of durations 0..i-1
3. In onUpdate, find which entry is active (last entry whose start ≤ time) and render it

The "dynamic" part: items with longer text get more screen time (formula: baseDuration + textLength * msPerChar). No hardcoded from / durationInFrames per item.

HTML

<div
  class="scene"
  id="seq-scene"
  data-composition-id="seq-scene"
  data-start="0"
  data-duration="{DURATION}"
  data-track-index="0"
>
  <div class="display">
    <div class="eyebrow" id="eyebrow">{eyebrow}</div>
    <div class="title" id="title"></div>
    <div class="body" id="body"></div>
    <div class="progress-bar"><div class="progress-fill" id="progress-fill"></div></div>
  </div>
  <div class="brand">— {Brand}</div>
</div>

CSS

Placeholders: {font} is the project sans-serif stack; {bgColor1}/{bgColor2} make the dark backdrop gradient; {accentColor} highlights the eyebrow / brand / progress fill; {textColor} is the primary readable foreground.

.scene {
  position: relative;
  width: 100%;
  height: 100%;
  display: grid;
  place-items: center;
  background: radial-gradient(ellipse at center, {bgColor1} 0%, {bgColor2} 70%);
  font-family: {font};
}
.display {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 32px;
  text-align: center;
  max-width: 1400px;
}
.eyebrow {
  font-size: 32px;
  font-weight: 800;
  letter-spacing: 14px;
  color: {accentColor};
  text-transform: uppercase;
}
.title {
  font-size: 120px;
  font-weight: 900;
  letter-spacing: -2px;
  line-height: 1;
  color: {textColor};
}
.body {
  font-size: 48px;
  font-weight: 500;
  line-height: 1.4;
  color: {accentColor};
  opacity: 0.9;
  min-height: 160px; /* reserve space so layout doesn't jump */
}
.progress-bar {
  width: 600px;
  height: 4px;
  background: {accentColor}26; /* ~15% alpha */
  border-radius: 2px;
  margin-top: 16px;
  overflow: hidden;
}
.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, {accentColor} 0%, {accentColor2} 100%);
  width: 0%;
}
.brand {
  position: absolute;
  bottom: 80px;
  left: 50%;
  transform: translateX(-50%);
  font-size: 32px;
  font-weight: 900;
  letter-spacing: 12px;
  color: {accentColor};
}

GSAP Timeline

<script src="https://cdn.jsdelivr.net/npm/gsap@3.14.2/dist/gsap.min.js"></script>
<script>
  window.__timelines = window.__timelines || {};
  const tl = gsap.timeline({ paused: true });

  // Content array — N entries, each with its own pacing config.
  // Shape: short eyebrow label, short title, longer body sentence, plus per-entry pacing.
  // The final entry typically uses a larger `hold` (closing beat).
  const CONTENT = [
    {
      eyebrow: "{eyebrow1}",
      title: "{title1}",
      body: "{body1}",
      speedFactor: SPEED_FACTOR,
      hold: HOLD_MID,
    },
    {
      eyebrow: "{eyebrow2}",
      title: "{title2}",
      body: "{body2}",
      speedFactor: SPEED_FACTOR,
      hold: HOLD_MID,
    },
    // …
    {
      eyebrow: "{eyebrowN}",
      title: "{titleN}",
      body: "{bodyN}",
      speedFactor: SPEED_FACTOR,
      hold: HOLD_FINAL,
    },
  ];

  // Pre-compute absolute start times.
  // Duration per entry: BASE_DURATION + body.length * SEC_PER_CHAR + entry.hold seconds.
  // BASE_DURATION, SEC_PER_CHAR documented in How to Choose Values.
  let cumulative = 0;
  const TIMELINE = CONTENT.map((entry) => {
    const dur = BASE_DURATION + entry.body.length * SEC_PER_CHAR + entry.hold;
    const start = cumulative;
    cumulative += dur;
    return { ...entry, start, end: cumulative };
  });

  // Reverse-search current entry
  function entryAt(time) {
    for (let i = TIMELINE.length - 1; i >= 0; i--) {
      if (time >= TIMELINE[i].start) return TIMELINE[i];
    }
    return TIMELINE[0];
  }

  const eyebrowEl = document.getElementById("eyebrow");
  const titleEl = document.getElementById("title");
  const bodyEl = document.getElementById("body");
  const progressEl = document.getElementById("progress-fill");

  const TOTAL_DURATION = cumulative + TAIL_PAD;
  const driver = { t: 0 };
  let lastTitle = "";

  tl.to(
    driver,
    {
      t: TOTAL_DURATION,
      duration: TOTAL_DURATION,
      ease: "none",
      onUpdate: () => {
        const entry = entryAt(driver.t);
        // Only swap content on transitions (avoid per-frame DOM thrash)
        if (entry.title !== lastTitle) {
          eyebrowEl.textContent = entry.eyebrow;
          titleEl.textContent = entry.title;
          bodyEl.textContent = entry.body;
          lastTitle = entry.title;
        }
        // Progress bar fills 0% → 100% as composition advances
        progressEl.style.width = `${(driver.t / TOTAL_DURATION) * 100}%`;
      },
    },
    0,
  );

  window.__timelines["seq-scene"] = tl;
</script>

Variations

Crossfade between items (not hard cut)

Add overlap to the find function — return BOTH the previous and next entry during the overlap window, render with crossfade opacity:

function activeEntries(time, overlap = 0.3) {
  const result = [];
  TIMELINE.forEach((e) => {
    if (time >= e.start - overlap && time <= e.end + overlap) result.push(e);
  });
  return result;
}

Then render the two adjacent entries with computed opacities based on distance from boundary.

Per-item motion variation

Each entry has its own motion style. Map entry.style to one of the existing rules: chapter 1 uses 3d-text-depth-layers, chapter 2 uses hacker-flip-3d, chapter 3 uses counting-dynamic-scale. The sequencer just orchestrates timing; per-entry rendering uses the appropriate rule.

Auto-extend composition duration

If you don't know upfront how long the sequence will be (dynamic content count), bind data-duration to the computed TOTAL_DURATION. Do this in script BEFORE the timeline registers:

document
  .querySelector("[data-composition-id]")
  .setAttribute("data-duration", String(Math.ceil(TOTAL_DURATION)));

(Caveat: HF reads data-duration at composition load; setting after init may not take effect — author the duration manually based on a rough TOTAL calc.)

Key Principles

• Pre-compute timeline once, not per-frame — building absolute start/end at script init means onUpdate is O(log n) reverse-search, not O(n²).
• Per-item duration formula: BASE_DURATION + body.length × SEC_PER_CHAR + hold — longer text needs more reading time. The formula is the load-bearing teaching of this rule; ranges for each const are in How to Choose Values.
• Reserve min-height on body element — content height varies per item; without reservation, layout jumps and downstream elements (progress bar, brand) jitter.
• DOM update on transition, not every frame — track lastTitle (or whatever key) and only call textContent = when it changes. Per-frame textContent assignment causes flicker in HF render.
• Optional progress indicator — a thin bar at the bottom showing 0-100% completes the "this is a sequence" framing.
• Climax dwell longer than mid-sequence dwell — the outro's hold (HOLD_FINAL) should exceed the in-sequence hold (HOLD_MID) so the final brand/CTA lands.

How to Choose Values

• BASE_DURATION — minimum visible time of an entry regardless of content length

  • Range: 0.6-1.5 s
  • Effects: low end snaps through short entries too fast for the eye; high end stalls on short titles
  • Constraints: ensures even one-word entries have time to read
  • Reference: see ../../examples/messaging-multi-phrase.html (and any blueprint that uses this rule)

• SEC_PER_CHAR — extra time added per body character

  • Range: 0.03-0.06 s/char (≈ 17-33 chars/sec read pace for video)
  • Effects: low end feels rushed for paragraph-style bodies; high end feels slow when bodies are short
  • Constraints: should be uniform across the sequence so the pace reads as one engine; for languages with wider characters, lean to the high end
  • Reference: see ../../examples/messaging-multi-phrase.html (and any blueprint that uses this rule)

• HOLD_MID — dwell after the typing of a non-final entry completes

  • Range: 0.5-1.0 s
  • Effects: low end feels rushed; high end feels lazy
  • Constraints: HOLD_MID < HOLD_FINAL
  • Reference: see ../../examples/messaging-multi-phrase.html (and any blueprint that uses this rule)

• HOLD_FINAL — dwell on the last entry (outro / climax)

  • Range: 1.0-2.0 s
  • Effects: low end truncates the closing beat; high end overstays
  • Constraints: must exceed HOLD_MID by a clear margin so the close reads as a beat, not another mid-sequence pause
  • Reference: see ../../examples/messaging-multi-phrase.html (and any blueprint that uses this rule)

• SPEED_FACTOR — per-entry pacing multiplier

  • Range: 0.5-2.0 (default 1.0)
  • Effects: <1 stretches an entry's body-driven duration (good for high-density passages); >1 compresses it
  • Constraints: discrete choice — use 1.0 unless one entry needs special pacing; if every entry uses the same factor, fold it into SEC_PER_CHAR instead
  • Reference: see ../../examples/messaging-multi-phrase.html (and any blueprint that uses this rule)

• TAIL_PAD — seconds added to TOTAL_DURATION after the last entry's end

  • Range: 0.0-1.0 s
  • Effects: 0 ends the driver exactly at the last hold completion; >0 leaves a quiet beat (useful before a transition to the next composition)
  • Constraints: if downstream is another composition, prefer 0 and handle the breath at the composition seam
  • Reference: see ../../examples/messaging-multi-phrase.html (and any blueprint that uses this rule)

• CONTENT length (N) — number of entries in the sequence

  • Range: 3-6 entries
  • Effects: <3 isn't a sequence (use a static scene); >6 drags
  • Constraints: each entry's title must fit one line at the chosen .title fontSize; bodies should fit within min-height after wrapping
  • Reference: see ../../examples/messaging-multi-phrase.html (and any blueprint that uses this rule)

Critical Constraints

• Timeline must be paused: gsap.timeline({ paused: true })
• Registry key = data-composition-id
• Pre-compute the TIMELINE array — don't recompute in onUpdate
• min-height on body for layout stability
• DOM swap only on entry transition — use lastTitle/lastKey guard
• Sequential only — for parallel tracks, use a different reduction (this rule is sequential)

Combinations

• discrete-text-sequence.md — per-entry typewriter on the body
• context-sensitive-cursor.md — cursor color per chapter segment
• vertical-spring-ticker.md — animated word transitions between items (instead of hard cut)
• scale-swap-transition.md — visual morph between entries

Pairs with HF skills

• /hyperframes-animation — single driver, reverse-search dispatch
• /hyperframes-core — composition wiring
• /hyperframes-cli — hyperframes lint