08Rim Glow Whose Intensity a Tilt-magnitude Value Sets

<main class="stage">
<div class="rg is-demo" id="rg">
  <p class="rg__hint"><span>Only the tilt magnitude (regardless of direction) is picked out and turned into the rim's glow radius and brightness</span></p>
  <div class="rg__scene" id="scene">
    <button class="rg__btn" id="btn" type="button" aria-label="Play now — button whose rim brightens with the tilt magnitude">
      <span class="rg__label">Play now</span>
    </button>
  </div>
</div>
</main>

@use "../../../../site/static/demo-tokens" as *;
@include stage($stage-paper);

.rg {
  display: grid;
  gap: $sp-4;
  justify-items: center;
}

.rg__hint {
  margin: 0;
  font-size: 13px;
  line-height: 1.5;
  text-align: center;
  max-width: 260px;
  color: rgba($subject-ink, .72);
}

.rg__scene {
  perspective: 640px;
  padding: $sp-6;
}

.rg__btn {
  position: relative;
  border: 0;
  cursor: pointer;
  padding: $sp-4 $sp-8;
  border-radius: $r-control;
  background: $subject-ink;
  color: $subject-cream;
  font-size: 16px;
  font-weight: 700;
  transform-style: preserve-3d;
  will-change: transform, box-shadow;
}

.rg__btn:focus-visible {
  outline: 2px solid $subject-blue-light;
  outline-offset: 3px;
}

.rg__label {
  position: relative;
  z-index: 1;
}

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

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

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

.rg {
  display: grid;
  gap: 16px;
  justify-items: center;
}

.rg__hint {
  margin: 0;
  font-size: 13px;
  line-height: 1.5;
  text-align: center;
  max-width: 260px;
  color: rgba(23, 20, 26, 0.72);
}

.rg__scene {
  perspective: 640px;
  padding: 24px;
}

.rg__btn {
  position: relative;
  border: 0;
  cursor: pointer;
  padding: 16px 32px;
  border-radius: 12px;
  background: #17141a;
  color: #fff7e6;
  font-size: 16px;
  font-weight: 700;
  transform-style: preserve-3d;
  will-change: transform, box-shadow;
}

.rg__btn:focus-visible {
  outline: 2px solid #5b8cf8;
  outline-offset: 3px;
}

.rg__label {
  position: relative;
  z-index: 1;
}

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

(function () {
  var root = document.getElementById('rg');
  var scene = document.getElementById('scene');
  var btn = document.getElementById('btn');
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var MAX_DEG = 10;
  var LERP = 0.16;
  var BLUR_BASE = 6;
  var BLUR_RANGE = 34;
  var targetNX = 0, targetNY = 0, curNX = 0, curNY = 0;
  var hasPointer = false;

  function clamp(v, lo, hi) { return Math.max(lo, Math.min(hi, v)); }
  function syntheticTarget(t) { return [Math.sin(t * 1.1 + 0.3), Math.sin(t * 1.6)]; }

  // 방향은 회전에만 쓰고, 둘레 광은 크기(magnitude)만 읽는다 — 05 의 방향성 광과 다른 값이다
  function render(nx, ny) {
    btn.style.transform = 'rotateX(' + (-ny * MAX_DEG).toFixed(2) + 'deg) rotateY(' + (nx * MAX_DEG).toFixed(2) + 'deg)';
    var mag = clamp(Math.sqrt(nx * nx + ny * ny), 0, 1);
    var blur = BLUR_BASE + mag * BLUR_RANGE;
    var spread = 1 + mag * 5;
    var alpha = (0.28 + mag * 0.5).toFixed(2);
    btn.style.boxShadow = '0 0 ' + blur.toFixed(1) + 'px ' + spread.toFixed(1) + 'px rgba(91,140,248,' + alpha + '), 0 12px 20px rgba(23,20,26,.28)';
  }

  var t0 = null;
  function loop(now) {
    if (t0 === null) t0 = now;
    var t = (now - t0) / 1000;
    if (!hasPointer && !reduce) {
      var s = syntheticTarget(t);
      targetNX = s[0]; targetNY = s[1];
    }
    curNX += (targetNX - curNX) * LERP;
    curNY += (targetNY - curNY) * LERP;
    render(curNX, curNY);
    requestAnimationFrame(loop);
  }

  function pointFromEvent(e) {
    var r = scene.getBoundingClientRect();
    var nx = ((e.clientX - r.left) / r.width) * 2 - 1;
    var ny = ((e.clientY - r.top) / r.height) * 2 - 1;
    return [clamp(nx, -1, 1), clamp(ny, -1, 1)];
  }

  scene.addEventListener('pointermove', function (e) {
    hasPointer = true;
    root.classList.remove('is-demo');
    var p = pointFromEvent(e);
    targetNX = p[0]; targetNY = p[1];
  });
  scene.addEventListener('pointerleave', function () {
    hasPointer = false;
    targetNX = 0; targetNY = 0;
  });
  btn.addEventListener('click', function () {
    root.classList.remove('is-demo');
    hasPointer = true;
    targetNX = 0.95; targetNY = 0.3;
    if (reduce) { render(targetNX, targetNY); }
    setTimeout(function () { if (!hasPointer) { targetNX = 0; targetNY = 0; if (reduce) { render(targetNX, targetNY); } } }, 240);
  });
  btn.addEventListener('keydown', function (e) {
    var step = 0.24;
    var moves = { ArrowLeft: [-step, 0], ArrowRight: [step, 0], ArrowUp: [0, -step], ArrowDown: [0, step] };
    var m = moves[e.key];
    if (!m) return;
    e.preventDefault();
    root.classList.remove('is-demo');
    hasPointer = true;
    targetNX = clamp(targetNX + m[0], -1, 1);
    targetNY = clamp(targetNY + m[1], -1, 1);
    if (reduce) { render(targetNX, targetNY); }
  });

  if (reduce) {
    render(0.5, 0.4);
  } else {
    requestAnimationFrame(loop);
  }
})();

// RimGlowButton — vanilla 판(run/393/demo/08-pointer-tilt-3d-rim-glow/index.html) 의 React 포트.
// 기울기 벡터에서 방향은 회전에만 쓰고, 크기(magnitude)만 따로 읽어 둘레 광의 반경·번짐·밝기로
// 바꾼다(05 의 방향성 테두리 광과는 다른 값). 값·수치는 vanilla 와 같다.
import { useEffect, useRef, useState } from "react";
import type { PointerEvent as ReactPointerEvent } from "react";
import styles from "./RimGlowButton.module.scss";

type Box<T> = { current: T };
type KeyEvt = { key: string; preventDefault(): void };

const MAX_DEG = 10;
const LERP = 0.16;
const BLUR_BASE = 6;
const BLUR_RANGE = 34;
const LABEL = "지금 플레이 — 기울기 크기로 둘레가 밝아지는 버튼";

function clamp(v: number, lo: number, hi: number): number {
  return Math.max(lo, Math.min(hi, v));
}
function syntheticTarget(t: number): [number, number] {
  return [Math.sin(t * 1.1 + 0.3), Math.sin(t * 1.6)];
}

export default function RimGlowButton() {
  const sceneRef = useRef<HTMLDivElement | null>(null);
  const btnRef = useRef<HTMLButtonElement | null>(null);
  const targetXRef = useRef<number>(0) as Box<number>;
  const targetYRef = useRef<number>(0) as Box<number>;
  const curXRef = useRef<number>(0) as Box<number>;
  const curYRef = useRef<number>(0) as Box<number>;
  const hasPointerRef = useRef<boolean>(false) as Box<boolean>;
  const frameRef = useRef<number>(0) as Box<number>;
  const t0Ref = useRef<number>(0) as Box<number>;
  const [demo, setDemo] = useState(true);
  const [reduce, setReduce] = useState(false);

  function render(nx: number, ny: number): void {
    const btn = btnRef.current;
    if (!btn) return;
    btn.style.transform = "rotateX(" + (-ny * MAX_DEG).toFixed(2) + "deg) rotateY(" + (nx * MAX_DEG).toFixed(2) + "deg)";
    const mag = clamp(Math.sqrt(nx * nx + ny * ny), 0, 1);
    const blur = BLUR_BASE + mag * BLUR_RANGE;
    const spread = 1 + mag * 5;
    const alpha = (0.28 + mag * 0.5).toFixed(2);
    btn.style.boxShadow = "0 0 " + blur.toFixed(1) + "px " + spread.toFixed(1) + "px rgba(91,140,248," + alpha + "), 0 12px 20px rgba(23,20,26,.28)";
  }

  useEffect(() => {
    setReduce(window.matchMedia("(prefers-reduced-motion: reduce)").matches);
  }, []);

  useEffect(() => {
    if (reduce) {
      render(0.5, 0.4);
      return;
    }
    function loop(now: number): void {
      if (t0Ref.current === 0) t0Ref.current = now;
      const t = (now - t0Ref.current) / 1000;
      if (!hasPointerRef.current) {
        const s = syntheticTarget(t);
        targetXRef.current = s[0];
        targetYRef.current = s[1];
      }
      curXRef.current += (targetXRef.current - curXRef.current) * LERP;
      curYRef.current += (targetYRef.current - curYRef.current) * LERP;
      render(curXRef.current, curYRef.current);
      frameRef.current = requestAnimationFrame(loop);
    }
    frameRef.current = requestAnimationFrame(loop);
    return () => cancelAnimationFrame(frameRef.current);
  }, [reduce]);

  function pointFromEvent(event: ReactPointerEvent<HTMLDivElement>): [number, number] {
    const scene = sceneRef.current;
    if (!scene) return [0, 0];
    const r = scene.getBoundingClientRect();
    const nx = ((event.clientX - r.left) / r.width) * 2 - 1;
    const ny = ((event.clientY - r.top) / r.height) * 2 - 1;
    return [clamp(nx, -1, 1), clamp(ny, -1, 1)];
  }

  function onPointerMove(event: ReactPointerEvent<HTMLDivElement>): void {
    hasPointerRef.current = true;
    setDemo(false);
    const p = pointFromEvent(event);
    targetXRef.current = p[0];
    targetYRef.current = p[1];
  }

  function onPointerLeave(): void {
    hasPointerRef.current = false;
    targetXRef.current = 0;
    targetYRef.current = 0;
  }

  function onClick(): void {
    setDemo(false);
    hasPointerRef.current = true;
    targetXRef.current = 0.95;
    targetYRef.current = 0.3;
    if (reduce) render(targetXRef.current, targetYRef.current);
    window.setTimeout(() => {
      if (!hasPointerRef.current) {
        targetXRef.current = 0;
        targetYRef.current = 0;
        if (reduce) render(targetXRef.current, targetYRef.current);
      }
    }, 240);
  }

  function onKeyDown(event: KeyEvt): void {
    const step = 0.24;
    const moves: { [key: string]: [number, number] } = {
      ArrowLeft: [-step, 0],
      ArrowRight: [step, 0],
      ArrowUp: [0, -step],
      ArrowDown: [0, step],
    };
    const m = moves[event.key];
    if (!m) return;
    event.preventDefault();
    setDemo(false);
    hasPointerRef.current = true;
    targetXRef.current = clamp(targetXRef.current + m[0], -1, 1);
    targetYRef.current = clamp(targetYRef.current + m[1], -1, 1);
    if (reduce) render(targetXRef.current, targetYRef.current);
  }

  const cls = [styles.rg, demo ? styles.isDemo : ""].filter(Boolean).join(" ");
  return (
    <main className={styles.stage}>
      <div className={cls}>
        <p className={styles.hint}>
          <span>기울기 크기(방향과 무관)만 골라 둘레 전체의 광 반경·밝기로 바꿉니다</span>
        </p>
        <div className={styles.scene} ref={sceneRef} onPointerMove={onPointerMove} onPointerLeave={onPointerLeave}>
          <button className={styles.btn} ref={btnRef} type="button" aria-label={LABEL} onClick={onClick} onKeyDown={onKeyDown}>
            <span className={styles.label}>지금 플레이</span>
          </button>
        </div>
      </div>
    </main>
  );
}