frames/skills/frames-animation/rules/counting-dynamic-scale.md

name, description, metadata

name	description	metadata
counting-dynamic-scale	Counter animation where the value counts up while transform scale grows to its final size, creating escalating visual weight without per-frame text reflow.	tags counter, counting, scale, transform, number, dynamic, emphasis

Counting with Dynamic Scale

A number counts from A → B while its transform scale grows to the final size — escalating visual weight ("this is impressive") without tweening font-size or forcing text layout on every frame. The final font size is static CSS; only the transform changes.

How It Works

Two synchronized tweens at the SAME timeline position with the SAME ease: (1) a proxy value rendered as text via onUpdate (Math.round(...).toLocaleString()), (2) the counter's transform scale: START_SCALE → 1, where START_SCALE = START_SIZE / END_SIZE. A suffix (%, ×, +) slides in AFTER the count lands — the number gets its own beat — and a label fades in early.

Recipe

<!-- inside a standard scene clip (frames-core) -->
<div class="counter-wrap">
  <span class="counter" id="counter">0</span><span class="counter-suffix">{suffix}</span>
</div>
<div class="counter-label">{label}</div>

.counter-wrap {
  display: flex;
  align-items: baseline;
  justify-content: center;
  width: {counterContainerWidth}; /* fixed width — no layout shift as digit count changes */
}
.counter {
  font-variant-numeric: tabular-nums; /* MANDATORY — digits keep equal width */
  display: inline-block;
  font-size: {endSize}; /* final size is static; GSAP animates scale, not font-size */
  transform-origin: center center;
}
.counter-suffix {
  opacity: 0;
  transform: translateY(20px);
}

const counter = document.getElementById("counter");
const state = { value: 0 };
const START_SCALE = START_SIZE / END_SIZE;

// Count value — onUpdate changes text only
tl.to(
  state,
  {
    value: TARGET_VALUE,
    duration: COUNT_DUR,
    ease: COUNT_EASE,
    onUpdate: () => {
      counter.textContent = Math.round(state.value).toLocaleString();
    },
  },
  0,
);

// Visual growth — compositor transform sharing the count's timing + ease
tl.fromTo(counter, { scale: START_SCALE }, { scale: 1, duration: COUNT_DUR, ease: COUNT_EASE }, 0);

// Suffix slides in AFTER the count completes
tl.to(
  ".counter-suffix",
  { opacity: 1, y: 0, duration: SUFFIX_DUR, ease: `back.out(${SUFFIX_BOUNCE_FACTOR})` },
  COUNT_DUR,
);

// Label fades in early
tl.from(".counter-label", { opacity: 0, y: 12, duration: LABEL_DUR, ease: "power2.out" }, LABEL_AT);

Variations

• Direct innerText tween (no proxy) — GSAP can tween innerText directly for a number-only counter; keep the proxy form when you need locale formatting or suffix logic. The scale tween stays separate either way:

tl.to(
  counter,
  { innerText: TARGET_VALUE, duration: COUNT_DUR, ease: COUNT_EASE, snap: { innerText: 1 } },
  0,
);

• 3D depth entry — add a tl.from(".counter", { z: -300, ... }, 0) push-in; requires perspective on .counter-wrap and transform-style: preserve-3d on the counter.
• Multi-stat coordinated reveal — 3 stats counting in parallel share the SAME ease, duration, and start position so they finish together (a chord, not an arpeggio). Each stat usually also needs a paired graphic (bar / ring / stars) — don't stop at the number; see stat-bars-and-fills.md.

Values

token	range	notes
TARGET_VALUE	2–3 digits ideal	4+ digits needs a wider container; must fit at END_SIZE without clipping
START_SIZE / END_SIZE	START ≈ 40–60% of END	design inputs used once for START_SCALE; never tween either
COUNT_DUR	1.2–2.5s	below ~0.8s reads as a flash — the eye must read the digits scrolling past
COUNT_EASE	power2.out / power3.out ⭐ / expo.out	shared by value + scale; more .out = more dramatic deceleration at the peak
SUFFIX_DUR	0.3–0.6s	fires at COUNT_DUR, never during the count
SUFFIX_BOUNCE_FACTOR	1.4–2.0	overshoot is fine on the suffix (it's punctuation, not data)
LABEL_AT / LABEL_DUR	AT < COUNT_DUR/2; 0.4–0.7s	label arrives before the count peaks

Critical Constraints

• tabular-nums mandatory + fixed-width container as belt-and-suspenders — without them digit-count transitions (9 → 10 → 100) jitter as glyph widths change.
• Never set fontSize in onUpdate — final type size is static CSS; only the transform changes per frame. Keep onUpdate O(1): set text only, no style writes or DOM creation.
• Math.round, not Math.floor — halfway through the final integer should already display the final value.
• Avoid back.out / elastic.out on the counter itself — overshoot makes the number look unstable (it's data, not decoration). Grow in place, don't bounce.
• Label is BIG TEXT, not a page-style caption — a tiny paragraph under a hero-size number reads as visual noise in video. Display-size, uppercase, tracked: the label is part of the headline.

See also

stat-bars-and-fills (the paired graphic — give it the same ease/duration so number and fill land as one beat) · svg-path-draw (icons drawing in around the number) · center-outward-expansion (icons bursting outward at the count peak).