02Letter-by-letter bounce

<main class="stage">
  <h1 class="letters" data-split>GODRICH</h1>
</main>

@use "../../../../site/static/demo-tokens" as *;

$duration: $dur-loop;                             // 글자들이 한 바퀴 도는 시간 (시차는 $stagger)
$easing: $ease-pop;                                // 아래에서 튀어오르는 느낌
$stagger: 40ms;                                    // --i 1당 시차

@include stage($stage-yellow);

.letters {
  margin: 0;
  display: flex;
  gap: clamp(2px, 1vw, 6px);
  font-weight: 800; font-size: clamp(28px, 10vw, 46px); line-height: 1; font-family: inherit;
  color: $subject-ink;

  span {
    display: inline-block;
    animation: letter-bounce $duration $easing infinite, letter-blur-in $duration $easing infinite;
    animation-delay: calc(var(--i) * #{$stagger} + var(--n) * 60ms);
  }
}

@keyframes letter-bounce {
  0%, 4%    { opacity: 0; transform: translateY(22px); }
  22%, 70%  { opacity: 1; transform: translateY(0); }
  88%, 100% { opacity: 0; transform: translateY(-14px); }
}

@keyframes letter-blur-in {
  0%, 4%    { filter: blur(10px); }
  22%, 70%  { filter: blur(0); }
  88%, 100% { filter: blur(10px); }
}

@media (prefers-reduced-motion: reduce) {
  .letters span { animation: none; opacity: 1; transform: none; filter: none; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffd23f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.letters {
  margin: 0;
  display: flex;
  gap: clamp(2px, 1vw, 6px);
  font-weight: 800;
  font-size: clamp(28px, 10vw, 46px);
  line-height: 1;
  font-family: inherit;
  color: #17141a;
}
.letters span {
  display: inline-block;
  animation: letter-bounce 2s cubic-bezier(0.2, 1.4, 0.4, 1) infinite, letter-blur-in 2s cubic-bezier(0.2, 1.4, 0.4, 1) infinite;
  animation-delay: calc(var(--i) * 40ms + var(--n) * 60ms);
}

@keyframes letter-bounce {
  0%, 4% {
    opacity: 0;
    transform: translateY(22px);
  }
  22%, 70% {
    opacity: 1;
    transform: translateY(0);
  }
  88%, 100% {
    opacity: 0;
    transform: translateY(-14px);
  }
}
@keyframes letter-blur-in {
  0%, 4% {
    filter: blur(10px);
  }
  22%, 70% {
    filter: blur(0);
  }
  88%, 100% {
    filter: blur(10px);
  }
}
@media (prefers-reduced-motion: reduce) {
  .letters span {
    animation: none;
    opacity: 1;
    transform: none;
    filter: none;
  }
}

(function(){
  function splitLetters(el){
    var text = el.textContent;
    el.textContent = "";
    Array.from(text).forEach(function(ch, i){
      var span = document.createElement("span");
      span.className = "letter";
      var seed = Math.sin((i + 1) * 12.9898) * 43758.5453;
      var noise = seed - Math.floor(seed);
      span.style.setProperty("--i", i);
      span.style.setProperty("--n", noise.toFixed(3));
      span.textContent = ch === " " ? " " : ch;
      el.appendChild(span);
    });
  }
  document.querySelectorAll("[data-split]").forEach(splitLetters);
})();

import type { CSSProperties } from "react";
import styles from "./LetterBounce.module.scss";

type Vars = CSSProperties & { "--i"?: number; "--n"?: number };

function noise(i: number): number {
  const s = Math.sin((i + 1) * 12.9898) * 43758.5453;
  return Number((s - Math.floor(s)).toFixed(3));
}

export type LetterBounceProps = {
  letters: string[];
  /** 글자들이 한 바퀴 도는 시간 ms (기본 2000) */
  duration?: number;
  /** --i 1당 시차 ms (기본 40ms) */
  stagger?: number;
  color?: string;
};

export default function LetterBounce({ letters, duration = 2000, color = "#17141a" }: LetterBounceProps) {
  return (
    <h1 className={styles.letters} style={{ "--color": color, "--duration": `${duration}ms` } as CSSProperties}>
      {letters.map((ch, i) => (
        <span key={i} style={{ "--i": i, "--n": noise(i) } as Vars}>{ch}</span>
      ))}
    </h1>
  );
}