09연속 색 값 전환 — 강도 값이 단계로 끊기지 않고 연속된 값으로 바뀌며 색상 값도 함께 매끄럽게 이어지는 방식

<main class="stage">
<div class="cm is-demo" id="cm">
  <label class="cm__field">
    <input class="cm__input" id="cmInput" type="text" autocomplete="off" spellcheck="false" value="">
  </label>
  <div class="cm__track"><div class="cm__fill" id="cmFill"></div></div>
  <div class="cm__readout">정도 <b id="cmPct">0</b>%</div>
</div>
</main>

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

// 계산 겹: 길이 비중·문자 종류 비중을 반씩 섞은 연속값(0~1)을 3개 색 정지점 사이에서
// RGB 선형보간해 매 입력마다 새 색을 계산한다 — 정해진 색 중 고르는 게 아니라 만든다.
@include stage($stage-ink);

.cm {
  width: 100%;
  max-width: 320px;
  display: grid;
  gap: $sp-4;
}

.cm__field { display: block; }

.cm__input {
  width: 100%;
  box-sizing: border-box;
  padding: $sp-3 $sp-4;
  border-radius: $r-control;
  border: 0;
  background: rgba($stage-paper, .12);
  color: $subject-cream;
  font: 500 16px/1.3 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  letter-spacing: .04em;
  -webkit-text-security: disc;

  &:focus { outline: 2px solid $subject-blue-light; outline-offset: 2px; }
}

.cm__track {
  position: relative;
  height: $sp-4;
  border-radius: $r-sm;
  background: rgba($stage-paper, .14);
  overflow: hidden;
}

.cm__fill {
  position: absolute;
  inset: 0;
  border-radius: $r-sm;
  background: $error;
  transform: scaleX(0);
  transform-origin: left center;
  transition: transform $dur-base $ease-out, background-color $dur-base $ease-out;
}

.cm__readout {
  font: 600 13px/1.2 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: $stage-paper;
  text-align: center;

  b { font-variant-numeric: tabular-nums; }
}

@media (max-width: 340px) {
  .cm { max-width: 260px; }
  .cm__input { padding: $sp-2 $sp-3; font-size: 14px; }
  .cm__readout { font-size: 11px; }
}

@media (prefers-reduced-motion: reduce) {
  .cm__fill { transition: none; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.cm {
  width: 100%;
  max-width: 320px;
  display: grid;
  gap: 16px;
}

.cm__field {
  display: block;
}

.cm__input {
  width: 100%;
  box-sizing: border-box;
  padding: 12px 16px;
  border-radius: 12px;
  border: 0;
  background: rgba(255, 255, 255, 0.12);
  color: #fff7e6;
  font: 500 16px/1.3 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  letter-spacing: 0.04em;
  -webkit-text-security: disc;
}
.cm__input:focus {
  outline: 2px solid #5b8cf8;
  outline-offset: 2px;
}

.cm__track {
  position: relative;
  height: 16px;
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.14);
  overflow: hidden;
}

.cm__fill {
  position: absolute;
  inset: 0;
  border-radius: 8px;
  background: #c2361a;
  transform: scaleX(0);
  transform-origin: left center;
  transition: transform 300ms ease-out, background-color 300ms ease-out;
}

.cm__readout {
  font: 600 13px/1.2 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: #ffffff;
  text-align: center;
}
.cm__readout b {
  font-variant-numeric: tabular-nums;
}

@media (max-width: 340px) {
  .cm {
    max-width: 260px;
  }
  .cm__input {
    padding: 8px 12px;
    font-size: 14px;
  }
  .cm__readout {
    font-size: 11px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .cm__fill {
    transition: none;
  }
}

(function () {
  var root = document.getElementById('cm');
  var input = document.getElementById('cmInput');
  var fill = document.getElementById('cmFill');
  var pctEl = document.getElementById('cmPct');

  // 계산 겹: 길이 비중·문자 종류 비중을 반씩 섞어 연속값(0~1)을 만들고, 그 값을
  // 3개 색 정지점(red→yellow→mint) 사이에서 RGB 선형보간해 매 입력마다 새로 계산한다.
  var STOPS = [
    { t: 0,    rgb: [194, 54, 26] },
    { t: 0.5,  rgb: [255, 210, 63] },
    { t: 1,    rgb: [76, 212, 166] }
  ];

  function lerp(a, b, f) { return a + (b - a) * f; }

  function colorAt(t) {
    t = Math.max(0, Math.min(1, t));
    var lo = STOPS[0], hi = STOPS[STOPS.length - 1];
    for (var i = 0; i < STOPS.length - 1; i++) {
      if (t >= STOPS[i].t && t <= STOPS[i + 1].t) { lo = STOPS[i]; hi = STOPS[i + 1]; break; }
    }
    var span = hi.t - lo.t || 1;
    var f = (t - lo.t) / span;
    var r = Math.round(lerp(lo.rgb[0], hi.rgb[0], f));
    var g = Math.round(lerp(lo.rgb[1], hi.rgb[1], f));
    var b = Math.round(lerp(lo.rgb[2], hi.rgb[2], f));
    return 'rgb(' + r + ',' + g + ',' + b + ')';
  }

  function classCount(value) {
    var n = 0;
    if (/[a-z]/.test(value)) n++;
    if (/[A-Z]/.test(value)) n++;
    if (/[0-9]/.test(value)) n++;
    if (/[^A-Za-z0-9]/.test(value)) n++;
    return n;
  }

  function scoreT(value) {
    var lengthPart = Math.min(1, value.length / 20);
    var classPart = classCount(value) / 4;
    return 0.5 * lengthPart + 0.5 * classPart;
  }

  function paint(value) {
    var t = scoreT(value);
    fill.style.transform = 'scaleX(' + t + ')';
    fill.style.backgroundColor = colorAt(t);
    pctEl.textContent = String(Math.round(t * 100));
  }

  input.addEventListener('input', function () {
    root.classList.remove('is-demo');
    stopAutoplay();
    paint(input.value);
  });

  paint(input.value);

  // 자동 루프: 시드 고정 문자열 배열로 길이·문자 종류를 함께 늘렸다 줄인다.
  var SEQ = ['', 'ab', 'abcdef', 'abcdefGH', 'abcdefGH12', 'abcdefGH12!@',
             'abcdefGH12', 'abcdefGH', 'abcdef', 'ab', ''];
  var si = 0;
  var autoTimer = null;
  function autoTick() { input.value = SEQ[si]; paint(SEQ[si]); si = (si + 1) % SEQ.length; }
  function stopAutoplay() { if (autoTimer) { clearInterval(autoTimer); autoTimer = null; } }
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (!reduce) { autoTimer = setInterval(autoTick, 380); autoTick(); }
})();

import { useEffect, useRef } from "react";
import styles from "./ColorGradientMorph.module.scss";

type Box<T> = { current: T };

type Stop = { t: number; rgb: [number, number, number] };
const STOPS: Stop[] = [
  { t: 0, rgb: [194, 54, 26] },
  { t: 0.5, rgb: [255, 210, 63] },
  { t: 1, rgb: [76, 212, 166] },
];

function lerp(a: number, b: number, f: number) { return a + (b - a) * f; }

function colorAt(t: number) {
  t = Math.max(0, Math.min(1, t));
  let lo = STOPS[0], hi = STOPS[STOPS.length - 1];
  for (let i = 0; i < STOPS.length - 1; i++) {
    if (t >= STOPS[i].t && t <= STOPS[i + 1].t) { lo = STOPS[i]; hi = STOPS[i + 1]; break; }
  }
  const span = hi.t - lo.t || 1;
  const f = (t - lo.t) / span;
  const r = Math.round(lerp(lo.rgb[0], hi.rgb[0], f));
  const g = Math.round(lerp(lo.rgb[1], hi.rgb[1], f));
  const b = Math.round(lerp(lo.rgb[2], hi.rgb[2], f));
  return "rgb(" + r + "," + g + "," + b + ")";
}

export default function ColorGradientMorph() {
  const rootRef = useRef(null) as unknown as Box<HTMLDivElement | null>;

  useEffect(() => {
    const root = rootRef.current;
    if (!root) return;
    const input = root.querySelector(`.${styles.input}`) as HTMLInputElement | null;
    const fill = root.querySelector(`.${styles.fill}`) as HTMLElement | null;
    const pctEl = root.querySelector(`.${styles.pct}`) as HTMLElement | null;
    if (!input || !fill || !pctEl) return;

    function classCount(value: string) {
      let n = 0;
      if (/[a-z]/.test(value)) n++;
      if (/[A-Z]/.test(value)) n++;
      if (/[0-9]/.test(value)) n++;
      if (/[^A-Za-z0-9]/.test(value)) n++;
      return n;
    }

    // 계산 겹: 길이 비중·문자 종류 비중을 반씩 섞어 연속값(0~1)을 만들고, 그 값을
    // 3개 색 정지점(red→yellow→mint) 사이에서 RGB 선형보간해 매 입력마다 새로 계산한다.
    function scoreT(value: string) {
      const lengthPart = Math.min(1, value.length / 20);
      const classPart = classCount(value) / 4;
      return 0.5 * lengthPart + 0.5 * classPart;
    }

    function paint(value: string) {
      const t = scoreT(value);
      fill!.style.transform = "scaleX(" + t + ")";
      fill!.style.backgroundColor = colorAt(t);
      pctEl!.textContent = String(Math.round(t * 100));
    }

    function onInput() {
      root!.classList.remove(styles["is-demo"]);
      stopAutoplay();
      paint(input!.value);
    }
    input.addEventListener("input", onInput);
    paint(input.value);

    // 자동 루프: 시드 고정 문자열 배열로 길이·문자 종류를 함께 늘렸다 줄인다.
    const SEQ = ["", "ab", "abcdef", "abcdefGH", "abcdefGH12", "abcdefGH12!@",
      "abcdefGH12", "abcdefGH", "abcdef", "ab", ""];
    let si = 0;
    let autoTimer: number | null = null;
    function autoTick() { input!.value = SEQ[si]; paint(SEQ[si]); si = (si + 1) % SEQ.length; }
    function stopAutoplay() { if (autoTimer !== null) { window.clearInterval(autoTimer); autoTimer = null; } }
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    if (!reduce) { autoTimer = window.setInterval(autoTick, 380); autoTick(); }

    return () => {
      stopAutoplay();
      input.removeEventListener("input", onInput);
    };
  }, []);

  return (
    <div ref={rootRef} className={`${styles.stage} ${styles.cm} ${styles["is-demo"]}`}>
      <label className={styles.field}>
        <input className={styles.input} type="text" autoComplete="off" spellCheck={false} defaultValue="" />
      </label>
      <div className={styles.track}><div className={styles.fill} /></div>
      <div className={styles.readout}>정도 <b className={styles.pct}>0</b>%</div>
    </div>
  );
}