05Button Where an Angle Value Lights Up the Edge

<main class="stage">
<div class="eb is-demo" id="eb">
  <p class="eb__hint"><span>Tilt magnitude becomes an angle, and a thin edge band brightens along that direction</span></p>
  <div class="eb__scene" id="scene">
    <span class="eb__floor" id="floor" aria-hidden="true"></span>
    <div class="eb__wrap" id="wrap">
      <button class="eb__btn" id="btn" type="button" aria-label="Learn more — button whose edge brightens with the tilt amount">
        <span class="eb__bevel" id="bevel" aria-hidden="true"></span>
        <span class="eb__label">Learn more</span>
      </button>
      <span class="eb__side" id="side" aria-hidden="true"></span>
    </div>
  </div>
</div>
</main>

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

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

.eb__hint {
  margin: 0;
  font-size: 13px;
  line-height: 1.5;
  text-align: center;
  max-width: 260px;
  color: rgba($subject-cream, .78);
}

.eb__scene {
  position: relative;
  perspective: 640px;
  padding: $sp-6;
}

// 바닥 그림자 — 기울기 방향으로 옮겨가며 면적을 만든다
.eb__floor {
  position: absolute;
  left: 50%;
  bottom: 4px;
  width: clamp(140px, 52vw, 250px);
  height: clamp(42px, 15.4vw, 74px);
  margin-left: clamp(-125px, -26vw, -70px);
  border-radius: 50%;
  background: radial-gradient(closest-side, rgba($subject-blue-light, .7), rgba($subject-blue-light, 0) 72%);
  filter: blur(10px);
  pointer-events: none;
}

.eb__wrap {
  position: relative;
  display: inline-block;
}

.eb__btn {
  position: relative;
  border: 1px solid rgba($subject-cream, .16);
  cursor: pointer;
  padding: $sp-6 $sp-12;
  border-radius: $r-control;
  background: rgba(255, 247, 230, .06);
  color: $subject-cream;
  font-size: 16px;
  font-weight: 700;
  transform-style: preserve-3d;
  box-shadow: $shadow-raised;
  overflow: hidden;
  will-change: transform;
}

.eb__btn:focus-visible {
  outline: 2px solid $subject-cream;
  outline-offset: 3px;
}

.eb__bevel {
  position: absolute;
  inset: -2px;
  border-radius: inherit;
  padding: 4px;
  pointer-events: none;
  mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
  mask-composite: exclude;
  -webkit-mask-composite: xor;
}

// 측면 두께 — 버튼 아래 얇은 띠가 기운 크기만큼 길어져 옆면(두께)처럼 읽힌다
.eb__side {
  position: absolute;
  left: 8%;
  right: 8%;
  bottom: -4px;
  height: 10px;
  border-radius: 0 0 $r-control $r-control;
  background: linear-gradient(180deg, rgba($subject-blue-light, .6), rgba($subject-blue-deep, 0));
  transform-origin: top center;
  pointer-events: none;
}

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

@media (prefers-reduced-motion: reduce) {
  .eb__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: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

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

.eb__hint {
  margin: 0;
  font-size: 13px;
  line-height: 1.5;
  text-align: center;
  max-width: 260px;
  color: rgba(255, 247, 230, 0.78);
}

.eb__scene {
  position: relative;
  perspective: 640px;
  padding: 24px;
}

.eb__floor {
  position: absolute;
  left: 50%;
  bottom: 4px;
  width: clamp(140px, 52vw, 250px);
  height: clamp(42px, 15.4vw, 74px);
  margin-left: clamp(-125px, -26vw, -70px);
  border-radius: 50%;
  background: radial-gradient(closest-side, rgba(91, 140, 248, 0.7), rgba(91, 140, 248, 0) 72%);
  filter: blur(10px);
  pointer-events: none;
}

.eb__wrap {
  position: relative;
  display: inline-block;
}

.eb__btn {
  position: relative;
  border: 1px solid rgba(255, 247, 230, 0.16);
  cursor: pointer;
  padding: 24px 48px;
  border-radius: 12px;
  background: rgba(255, 247, 230, 0.06);
  color: #fff7e6;
  font-size: 16px;
  font-weight: 700;
  transform-style: preserve-3d;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  overflow: hidden;
  will-change: transform;
}

.eb__btn:focus-visible {
  outline: 2px solid #fff7e6;
  outline-offset: 3px;
}

.eb__bevel {
  position: absolute;
  inset: -2px;
  border-radius: inherit;
  padding: 4px;
  pointer-events: none;
  mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
  mask-composite: exclude;
  -webkit-mask-composite: xor;
}

.eb__side {
  position: absolute;
  left: 8%;
  right: 8%;
  bottom: -4px;
  height: 10px;
  border-radius: 0 0 12px 12px;
  background: linear-gradient(180deg, rgba(91, 140, 248, 0.6), rgba(10, 79, 232, 0));
  transform-origin: top center;
  pointer-events: none;
}

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

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

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

  var MAX_DEG = 13;   // 불변
  var LERP = 0.16;
  var targetNX = 0, targetNY = 0;
  var 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 * 1.2 + 0.6), Math.sin(t * 0.88)]; }

  // 기울기 벡터의 각도·크기 → conic-gradient 회전각·광 폭. 테두리 광의 위치는 기운 방향과 같다
  // 폭·대비를 키워 테두리 띠가 버튼 변 전체를 가로지르게 한다 — MAX_DEG(기울기 각) 값은 그대로
  function render(nx, ny) {
    var rotY = nx * MAX_DEG;
    var rotX = -ny * MAX_DEG;
    btn.style.transform = 'rotateX(' + rotX.toFixed(2) + 'deg) rotateY(' + rotY.toFixed(2) + 'deg)';
    var mag = clamp(Math.sqrt(nx * nx + ny * ny), 0, 1);
    var ang = Math.atan2(ny, nx) * 180 / Math.PI + 90;
    var width = 70 + mag * 110;
    var alpha = (0.38 + mag * 0.6).toFixed(2);
    bevel.style.background = 'conic-gradient(from ' + ang.toFixed(1) + 'deg, rgba(91,140,248,0), rgba(91,140,248,' + alpha + ') ' + (width / 2).toFixed(1) + 'deg, rgba(91,140,248,0) ' + width.toFixed(1) + 'deg)';
    // 바닥 그림자 — 기운 방향으로 옮겨간다
    var floorShift = nx * 46;
    floor.style.transform = 'translateX(' + floorShift.toFixed(1) + 'px) scale(' + (1 + mag * 0.4).toFixed(2) + ')';
    floor.style.opacity = (0.14 + mag * 0.7).toFixed(2);
    // 측면 두께 — 기운 크기만큼 버튼 아래 「옆면」이 길어져 3D 두께로 읽힌다(MAX_DEG 불변, 순수 표현 한 겹)
    side.style.transform = 'scaleY(' + (0.4 + mag * 2.6).toFixed(2) + ')';
    side.style.opacity = (0.25 + mag * 0.7).toFixed(2);
  }

  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 = 0.9; targetNY = 0.9;
    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, 0.5);
  } else {
    requestAnimationFrame(loop);
  }
})();

// EdgeBevelButton — vanilla 판(run/393/demo/05-pointer-tilt-3d-edge-bevel/index.html) 의 React 포트.
// 기울기 벡터의 각도(atan2)·크기를 conic-gradient 의 회전각·광 폭·투명도로 바꿔 테두리 띠가
// 기운 방향을 따라 밝아지게 한다. 값·수치는 vanilla 와 같다.
import { useEffect, useRef, useState } from "react";
import type { PointerEvent as ReactPointerEvent } from "react";
import styles from "./EdgeBevelButton.module.scss";

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

const MAX_DEG = 13; // 불변
const LERP = 0.16;
const LABEL = "자세히 보기 — 기울기 크기로 테두리가 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 * 1.2 + 0.6), Math.sin(t * 0.88)];
}

export default function EdgeBevelButton() {
  const sceneRef = useRef<HTMLDivElement | null>(null);
  const btnRef = useRef<HTMLButtonElement | null>(null);
  const bevelRef = useRef<HTMLSpanElement | null>(null);
  const floorRef = useRef<HTMLSpanElement | null>(null);
  const sideRef = useRef<HTMLSpanElement | 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;
    const bevel = bevelRef.current;
    const floor = floorRef.current;
    const side = sideRef.current;
    if (!btn || !bevel || !floor || !side) return;
    const rotY = nx * MAX_DEG;
    const rotX = -ny * MAX_DEG;
    btn.style.transform = "rotateX(" + rotX.toFixed(2) + "deg) rotateY(" + rotY.toFixed(2) + "deg)";
    const mag = clamp(Math.sqrt(nx * nx + ny * ny), 0, 1);
    const ang = (Math.atan2(ny, nx) * 180) / Math.PI + 90;
    const width = 70 + mag * 110;
    const alpha = (0.38 + mag * 0.6).toFixed(2);
    bevel.style.background =
      "conic-gradient(from " + ang.toFixed(1) + "deg, rgba(91,140,248,0), rgba(91,140,248," + alpha + ") " + (width / 2).toFixed(1) + "deg, rgba(91,140,248,0) " + width.toFixed(1) + "deg)";
    const floorShift = nx * 46;
    floor.style.transform = "translateX(" + floorShift.toFixed(1) + "px) scale(" + (1 + mag * 0.4).toFixed(2) + ")";
    floor.style.opacity = (0.14 + mag * 0.7).toFixed(2);
    side.style.transform = "scaleY(" + (0.4 + mag * 2.6).toFixed(2) + ")";
    side.style.opacity = (0.25 + mag * 0.7).toFixed(2);
  }

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

  useEffect(() => {
    if (reduce) {
      render(0.5, 0.5);
      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 = 0.9;
    targetYRef.current = 0.9;
    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.eb, demo ? styles.isDemo : ""].filter(Boolean).join(" ");
  return (
    <main className={styles.stage}>
      <div className={cls}>
        <p className={styles.hint}>
          <span>기울기 크기를 각도로 바꿔 얇은 테두리 띠가 그 방향을 따라 밝아집니다</span>
        </p>
        <div className={styles.scene} ref={sceneRef} onPointerMove={onPointerMove} onPointerLeave={onPointerLeave}>
          <span className={styles.floor} ref={floorRef} aria-hidden="true" />
          <div className={styles.wrap}>
            <button className={styles.btn} ref={btnRef} type="button" aria-label={LABEL} onClick={onClick} onKeyDown={onKeyDown}>
              <span className={styles.bevel} ref={bevelRef} aria-hidden="true" />
              <span className={styles.label}>자세히 보기</span>
            </button>
            <span className={styles.side} ref={sideRef} aria-hidden="true" />
          </div>
        </div>
      </div>
    </main>
  );
}