Top-Down Letters

<!--
  Top-Down Letters - remocn typography primitive for HyperFrames.

  Paste the markup, CSS and script into a composition. Drive the timeline
  integration from a paused GSAP timeline so renders remain deterministic.

  Variables. The script reads each one, falls back to the declared default on
  anything missing or unrecognised, and writes the result either into the
  markup or into a custom property the CSS above consumes. The timeline recipe
  below is untouched by them: it keeps driving one offset per letter, and these
  decide which letters fall, how far that offset carries them, and what colour
  they are.

    - text (string, default CASCADE): the word that cascades. Every character
      becomes one span, in source order, exactly like the hand-written markup;
      a space becomes a non-breaking space so it keeps its width in the flex
      row. Anything that is not a non-empty string keeps the shipped word.
    - distance (close | standard | far, default standard): multiplies the drop
      the timeline drives, so the letters cover a shorter or longer run in the
      same time. close covers half of it, standard leaves the shipped 42px
      alone, far carries them nearly double.
    - tone (ink | paper | accent, default ink): letter colour. ink is
      near-black for light frames, paper near-white for dark ones, accent
      rides --brand.

  On every default the result is identical to the original: the seven
  near-black letters of CASCADE dropping 42px into place.
-->

<div
  class="hf-remocn-top-down-letters"
  data-composition-variables='[
    { "id": "text", "type": "string", "role": "content", "label": "Text", "description": "Word that cascades in. Every character becomes one letter span, in source order.", "default": "CASCADE" },
    { "id": "distance", "type": "enum", "role": "motion", "label": "Distance", "description": "Multiplies the drop the timeline drives, so the letters cover a shorter or longer run in the same time.", "default": "standard", "options": [{ "value": "close", "label": "Close" }, { "value": "standard", "label": "Standard" }, { "value": "far", "label": "Far" }] },
    { "id": "tone", "type": "enum", "role": "style", "label": "Tone", "description": "Letter colour: ink for light frames, paper for dark ones, accent rides --brand.", "default": "ink", "options": [{ "value": "ink", "label": "Ink" }, { "value": "paper", "label": "Paper" }, { "value": "accent", "label": "Accent" }] }
  ]'
>
  <span>C</span><span>A</span><span>S</span><span>C</span><span>A</span><span>D</span><span>E</span>
</div>

<style>
  .hf-remocn-top-down-letters {
    color: var(--hf-letters-color, #18181b);
    font-family: Inter, system-ui, sans-serif;
    font-weight: 900;
    letter-spacing: -0.04em;
  }
  .hf-remocn-top-down-letters {
    display: inline-flex;
    gap: 1px;
    font-size: 74px;
    line-height: 0.9;
    overflow: hidden;
  }
  .hf-remocn-top-down-letters span {
    display: inline-block;
    transform: translateY(calc(var(--hf-char-y, 0px) * var(--hf-char-distance, 1)));
    will-change: transform, opacity;
  }
</style>

<script>
  (function () {
    "use strict";

    var vars =
      window.__hyperframes && window.__hyperframes.getVariables
        ? window.__hyperframes.getVariables()
        : {};

    // Unrecognised overrides return to their declared defaults.
    var distances = { close: 0.5, standard: 1, far: 1.8 };
    var tones = {
      ink: "#18181b",
      paper: "#fafafa",
      accent: "var(--brand, #34d399)",
    };

    function pick(table, value, fallback) {
      return Object.prototype.hasOwnProperty.call(table, value) ? value : fallback;
    }

    var distance = distances[pick(distances, vars.distance, "standard")];
    var tone = tones[pick(tones, vars.tone, "ink")];
    var text = typeof vars.text === "string" && vars.text !== "" ? vars.text : null;

    var roots = document.querySelectorAll(".hf-remocn-top-down-letters");
    for (var i = 0; i < roots.length; i += 1) {
      var root = roots[i];
      root.style.setProperty("--hf-char-distance", String(distance));
      root.style.setProperty("--hf-letters-color", tone);

      // Only rebuild when text was supplied; the shipped markup is already the
      // exact span-per-character output this branch produces for CASCADE.
      if (text !== null) {
        var characters = Array.from(text);
        root.textContent = "";
        for (var j = 0; j < characters.length; j += 1) {
          var span = document.createElement("span");
          span.textContent = characters[j] === " " ? "\u00a0" : characters[j];
          root.appendChild(span);
        }
        root.setAttribute("aria-label", text);
      }
    }
  })();
</script>

<!--
  Timeline integration:
  tl.fromTo('.hf-remocn-top-down-letters span', { opacity: 0, '--hf-char-y': '-42px' }, { opacity: 1, '--hf-char-y': '0px', duration: 0.22, stagger: 0.035, ease: 'power3.out' }, startTime);
-->