skills/hyperframes-animation/rules/discrete-text-sequence.md

---
name: discrete-text-sequence
description: Replace entire text states at frame thresholds for non-linear typing effects — typos, bulk additions, pauses, backspaces, simulated thinking.
metadata:
  tags: text, typing, discrete, threshold, non-linear, sequence
---

# Discrete Text Sequence

Instead of character-by-character typewriter, replace entire string states at time thresholds — enabling non-linear effects (typos, backspaces, bulk paste, "thinking" gaps) that smooth per-char typing can't achieve. If your effect is "type each character, no edits", this rule is overkill — use the smooth-slice variation below.

## How It Works

The typing is authored as a sparse array of `{ t, text }` states; on every `onUpdate` a **reverse search** finds the latest entry whose `t` has passed and renders its text. Display jumps between states with no animation between them — the realism comes from the schedule shape: fast keystroke clusters (0.06–0.20s apart), pauses at word breaks (0.3–0.6s), a typo, backspaces peeling back to the fork, then a bulk paste replacing many chars in one entry. A block cursor blinks via a deterministic sin square wave on the same timeline.

## Recipe

```html
<!-- inside a standard scene clip (hyperframes-core) -->
<div class="terminal">
  <div class="prompt">$</div>
  <div class="text-wrap">
    <span class="text" id="text"></span><span class="cursor" id="cursor">_</span>
  </div>
</div>
```

```css
.terminal {
  font-family: {monoFont}; /* monospace required — proportional jitters even in a fixed box */
  display: flex;
  align-items: baseline;
  font-size: TERMINAL_FONT_SIZE;
}
.text-wrap {
  display: inline-flex;
  align-items: baseline;
  min-width: TEXT_WRAP_MIN_WIDTH; /* ≥ widest state — stops right-edge jitter */
  white-space: nowrap;
}
.cursor {
  display: inline-block; /* inline ignores width */
  width: CURSOR_WIDTH;
}
```

```js
// Each entry shows from its t until the NEXT entry's t.
// Shape: keystrokes → typo → backspace to the fork → bulk paste → completion mark.
const SEQUENCE = [
  { t: 0.0, text: "" },
  { t: T_K1, text: "{p1}" }, // first keystrokes (~3-5 chars, 0.1-0.2s apart)
  { t: T_K2, text: "{p1 + ' ' + p2_typo}" }, // continuation containing a typo
  { t: T_BS, text: "{p1 + ' ' + p2_partial}" }, // backspace(s) — peel back to the fork
  { t: T_BULK, text: "{fullCorrectedText}" }, // bulk paste — many chars in one jump
  { t: T_DONE, text: "{fullCorrectedText + ' ✓'}" }, // completion marker
];

// Reverse-search for the latest entry whose t has passed
function textAt(time) {
  for (let i = SEQUENCE.length - 1; i >= 0; i--) {
    if (time >= SEQUENCE[i].t) return SEQUENCE[i].text;
  }
  return "";
}

const textEl = document.getElementById("text");
const cursorEl = document.getElementById("cursor");

const driver = { t: 0 };
tl.to(
  driver,
  {
    t: TOTAL_DURATION,
    duration: TOTAL_DURATION,
    ease: "none",
    onUpdate: () => {
      textEl.textContent = textAt(driver.t);
    },
  },
  0,
);

// Cursor blink — deterministic sin square wave, never a CSS animation
const blink = { p: 0 };
tl.to(
  blink,
  {
    p: Math.PI * 2 * BLINK_CYCLES,
    duration: TOTAL_DURATION,
    ease: "none",
    onUpdate: () => {
      cursorEl.style.opacity = Math.sin(blink.p) > 0 ? "1" : "0";
    },
  },
  0,
);
```

## Variations

- **Smooth character slice** (continuous typewriter — no pauses, no edits): faster to author but uniformly "machine-typed", missing the human realism:

```js
const fullText = "{fullPhrase}";
const len = { v: 0 };
tl.to(
  len,
  {
    v: fullText.length,
    duration: TYPE_DUR,
    ease: "power1.inOut",
    onUpdate: () => {
      textEl.textContent = fullText.substring(0, Math.floor(len.v));
    },
  },
  0,
);
```

- **Thinking pause** — hold one state for `THINK_HOLD_DUR` (0.8–2.0s; under 0.5s reads as a stutter, not thought) simply by leaving a gap before the next entry's `t`.
- **State pulse on completion** — when the final state lands, `tl.to(".text", { scale: 1.03–1.08, duration: 0.15–0.3, yoyo: true, repeat: 1 }, T_DONE)`.
- **Per-state color shift** — in `onUpdate`, branch on `driver.t` vs the milestones: success color after `T_DONE`, dim mid-edit, normal while typing.

## Values

| token               | range                                        | notes                                                                  |
| ------------------- | -------------------------------------------- | ---------------------------------------------------------------------- |
| TERMINAL_FONT_SIZE  | 48–96px                                      | full-bleed comps; smaller for terminal-style detail                    |
| TEXT_WRAP_MIN_WIDTH | ≥ widest state                               | measure with a hidden probe after `document.fonts.ready` if unsure     |
| milestone `t`s      | keystrokes 0.06–0.20s apart; pauses 0.3–0.6s | monotonically increasing; `T_DONE ≤ TOTAL_DURATION − ~1s` climax dwell |
| TYPE_DUR (smooth)   | `chars × 0.06–0.12s`                         | fast → relaxed                                                         |
| BLINK_CYCLES        | one cycle per 0.5–0.8s                       | `TOTAL_DURATION / 0.8 ≤ BLINK_CYCLES ≤ TOTAL_DURATION / 0.5`           |
| CURSOR_WIDTH        | ~0.3× font size                              | gap to text single-digit px so the cursor feels attached               |

## Critical Constraints

- **Reverse-search the array each frame** — O(n) with small n (≤30 typical); don't index by frame, the sequence is sparse.
- **`min-width` on the text wrap is mandatory** — without it the right edge jitters as state length changes.
- **Discrete jumps must be INSTANT** — any transition on the text turns the jump into a smear and kills the "typing" feel.
- **Cursor blink is sin/sequence-driven on the timeline**, `display: inline-block`, monospace font, `white-space: nowrap` (wrapping mid-state breaks the illusion; trailing spaces must survive).
- **Discrete vs smooth** — use discrete only for non-linear states (typos, pauses, bulk paste); plain typing takes the smooth-slice variation.

## See also

`context-sensitive-cursor` (same SEQUENCE pattern + segment-colored cursor) · `3d-text-depth-layers` (discrete text with layered depth) · `counting-dynamic-scale` (discrete label beside a smooth counter) · `press-release-spring` (post-completion press beat).