05Loader Whose Sphere-Surface Points Converge to a Single Point

<main class="stage">
<div class="ld" id="ld">
  <p class="ld__hint">Click or press the space bar to pause or restart</p>
  <div class="ld__field" id="field" role="application" aria-label="Sphere point-convergence test panel" tabindex="0">
    <div class="c3__scene">
      <div class="c3__sphere" id="sphere"></div>
    </div>
    <b class="ld__badge" aria-hidden="true"><span class="ld__badgeNum" id="pct">0%</span><span class="ld__badgeUnit">Progress</span></b>
  </div>
</div>
</main>

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

// 구면 점 수렴 로더 — 피보나치 구 분포 공식(고정, 무작위 없음)으로 점을 구 표면에 고르게 흩어 두고,
// 진행률 값이 오를수록 각 점의 좌표를 중심(0,0,0) 쪽으로 선형 수축시킨다. 값이 다 차면 모든 점이 한 점에 겹친다.
// 395(캔버스 rAF 물리)·393(포인터 tilt) 과 다른 축 — 구면 분포 공식으로 점을 배치하고 중심 수렴 비율을 계산한다.

$duration: $dur-loop;
$easing: linear;
$color: $subject-blue-deep;

@include stage($stage-ink);

.ld { display: flex; flex-direction: column; gap: $sp-2; width: 100%; max-width: 360px; }

.ld__hint {
  margin: 0;
  font-weight: 700; font-size: clamp(10px, 2.8vw, 12px); line-height: 1.35;
  color: rgba($subject-cream, .78);
  text-align: center;
}

.ld__field {
  position: relative; height: 208px;
  border-radius: $r-card; overflow: hidden;
  background: $subject-cream;
  box-shadow: inset 0 0 0 1px rgba($subject-ink, .16);
  cursor: pointer;
}
.ld__field:focus-visible { outline: 2px solid $subject-blue-light; outline-offset: 2px; }

.c3__scene { position: absolute; inset: 0; perspective: clamp(320px, 70vw, 480px); }

.c3__sphere { position: absolute; left: 50%; top: 50%; width: 0; height: 0; transform-style: preserve-3d; }

.c3__pt {
  position: absolute; left: 0; top: 0;
  width: 7px; height: 7px; margin: -3.5px 0 0 -3.5px;
  border-radius: 50%;
  background: $color;
  will-change: transform;
}

.ld__badge {
  position: absolute; right: $sp-2; top: $sp-2;
  display: flex; align-items: baseline; gap: $sp-1;
  padding: $sp-1 $sp-2; border-radius: $r-pill;
  background: rgba($subject-ink, .78);
  color: $subject-cream; font-weight: 700; font-size: 11px;
}
.ld__badgeNum { font-size: 13px; color: $stage-yellow; }
.ld__badgeUnit { font-weight: 700; }

@media (max-width: 340px) {
  .ld { gap: $sp-1; }
  .ld__field { height: 124px; }
  .ld__badge { font-size: 10px; padding: 0 $sp-1; }
  .ld__badgeNum { font-size: 11px; }
}

@media (prefers-reduced-motion: reduce) {
  .ld.is-still .ld__field { cursor: default !important; }
  .ld.is-still .ld__badge { opacity: .92 !important; }
}

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);
}

.ld {
  display: flex;
  flex-direction: column;
  gap: 8px;
  width: 100%;
  max-width: 360px;
}

.ld__hint {
  margin: 0;
  font-weight: 700;
  font-size: clamp(10px, 2.8vw, 12px);
  line-height: 1.35;
  color: rgba(255, 247, 230, 0.78);
  text-align: center;
}

.ld__field {
  position: relative;
  height: 208px;
  border-radius: 16px;
  overflow: hidden;
  background: #fff7e6;
  box-shadow: inset 0 0 0 1px rgba(23, 20, 26, 0.16);
  cursor: pointer;
}

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

.c3__scene {
  position: absolute;
  inset: 0;
  perspective: clamp(320px, 70vw, 480px);
}

.c3__sphere {
  position: absolute;
  left: 50%;
  top: 50%;
  width: 0;
  height: 0;
  transform-style: preserve-3d;
}

.c3__pt {
  position: absolute;
  left: 0;
  top: 0;
  width: 7px;
  height: 7px;
  margin: -3.5px 0 0 -3.5px;
  border-radius: 50%;
  background: #0a4fe8;
  will-change: transform;
}

.ld__badge {
  position: absolute;
  right: 8px;
  top: 8px;
  display: flex;
  align-items: baseline;
  gap: 4px;
  padding: 4px 8px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.78);
  color: #fff7e6;
  font-weight: 700;
  font-size: 11px;
}

.ld__badgeNum {
  font-size: 13px;
  color: #ffd23f;
}

.ld__badgeUnit {
  font-weight: 700;
}

@media (max-width: 340px) {
  .ld {
    gap: 4px;
  }
  .ld__field {
    height: 124px;
  }
  .ld__badge {
    font-size: 10px;
    padding: 0 4px;
  }
  .ld__badgeNum {
    font-size: 11px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .ld.is-still .ld__field {
    cursor: default !important;
  }
  .ld.is-still .ld__badge {
    opacity: 0.92 !important;
  }
}

(function () {
'use strict';
var root = document.getElementById('ld');
var field = document.getElementById('field');
var pctEl = document.getElementById('pct');
var sphere = document.getElementById('sphere');

var POINT_COUNT = 28;
var SPHERE_R = 78;
var GOLDEN_ANGLE = Math.PI * (3 - Math.sqrt(5)); // 피보나치 구 분포 각(고정 상수, 무작위 없음)
var ROT_TURNS = 0.5;

// 피보나치 구 분포 — 점 i 의 구면 좌표를 결정적으로 계산한다.
var BASE = [];
for (var i = 0; i < POINT_COUNT; i++) {
  var y = 1 - (i / (POINT_COUNT - 1)) * 2;
  var r = Math.sqrt(Math.max(0, 1 - y * y));
  var theta = GOLDEN_ANGLE * i;
  BASE.push([Math.cos(theta) * r * SPHERE_R, y * SPHERE_R, Math.sin(theta) * r * SPHERE_R]);
}

var pts = [];
for (var pi = 0; pi < POINT_COUNT; pi++) {
  var el = document.createElement('div');
  el.className = 'c3__pt';
  sphere.appendChild(el);
  pts.push(el);
}

var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
var LOOP = 2;
var REDUCE_P = 0.7;
var t0 = 0, raf = 0, paused = false, lastP = 0;

function render(p) {
  lastP = p;
  var rotY = (p * 360 * ROT_TURNS) % 360;
  var shrink = 1 - p; // 중심(0,0,0) 으로의 수렴 비율
  sphere.style.transform = 'rotateY(' + rotY + 'deg) rotateX(14deg)';
  for (var i = 0; i < POINT_COUNT; i++) {
    var b = BASE[i];
    var x = b[0] * shrink, y = b[1] * shrink, z = b[2] * shrink;
    pts[i].style.transform = 'translate3d(' + x + 'px,' + y + 'px,' + z + 'px)';
  }
  pctEl.textContent = Math.round(p * 100) + '%';
}

function frame(now) {
  if (!paused) { var t = (now - t0) / 1000; render((t % LOOP) / LOOP); }
  raf = requestAnimationFrame(frame);
}
function togglePause() {
  paused = !paused;
  root.classList.toggle('is-paused', paused);
  render(reduce ? REDUCE_P : lastP);
}
function restart() {
  t0 = performance.now();
  render(reduce ? REDUCE_P : 0);
}

field.addEventListener('click', function () { togglePause(); });
field.addEventListener('keydown', function (e) {
  if (e.key === ' ' || e.key === 'Enter') { e.preventDefault(); togglePause(); }
  else if (e.key === 'r' || e.key === 'R') { e.preventDefault(); restart(); }
});
window.addEventListener('resize', function () {
  if (paused || reduce) render(reduce ? REDUCE_P : lastP);
});

t0 = performance.now();
if (reduce) {
  root.classList.add('is-still');
  render(REDUCE_P);
} else {
  raf = requestAnimationFrame(frame);
}
})();

// SpherePointConverge — vanilla 판(run/399/demo/05-loader-3d-sphere-point-converge/index.html) 의 React 포트.
// 피보나치 구 분포 공식(고정, 무작위 없음)으로 점을 구 표면에 배치하고, 진행률 값이 오를수록
// 각 점의 좌표를 중심(0,0,0) 쪽으로 선형 수축시킨다.
// 395(캔버스 rAF 물리)·393(포인터 tilt) 과 다른 축 — 구면 분포 공식으로 점을 배치하고 중심 수렴 비율을 계산한다.
import { useEffect, useRef } from "react";
import type { CSSProperties } from "react";
import styles from "./SpherePointConverge.module.scss";

export type SpherePointConvergeProps = {
  duration?: string;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
type Box<T> = { current: T };
type KeyEvt = { key: string; preventDefault(): void };

const POINT_COUNT = 28;
const SPHERE_R = 78;
const GOLDEN_ANGLE = Math.PI * (3 - Math.sqrt(5));
const ROT_TURNS = 0.5;
const LOOP = 2;
const REDUCE_P = 0.7;
const FIELD_LABEL = "구면 점 수렴 진행 실험판";

const BASE: [number, number, number][] = Array.from({ length: POINT_COUNT }, (_, i) => {
  const y = 1 - (i / (POINT_COUNT - 1)) * 2;
  const r = Math.sqrt(Math.max(0, 1 - y * y));
  const theta = GOLDEN_ANGLE * i;
  return [Math.cos(theta) * r * SPHERE_R, y * SPHERE_R, Math.sin(theta) * r * SPHERE_R];
});

export default function SpherePointConverge({
  duration = "2s",
  easing = "linear",
  color = "#0a4fe8",
}: SpherePointConvergeProps) {
  const rootRef = useRef<HTMLDivElement | null>(null);
  const fieldRef = useRef<HTMLDivElement | null>(null);
  const sphereRef = useRef<HTMLDivElement | null>(null);
  const pctRef = useRef<HTMLSpanElement | null>(null);
  const ptsRef = useRef<(HTMLDivElement | null)[]>(new Array(POINT_COUNT).fill(null)) as Box<(HTMLDivElement | null)[]>;
  const pausedRef = useRef(false) as Box<boolean>;
  const lastPRef = useRef(0) as Box<number>;
  const t0Ref = useRef(0) as Box<number>;
  const rafRef = useRef(0) as Box<number>;
  const vars: Vars = { "--duration": duration, "--easing": easing, "--color": color };

  function reduced(): boolean {
    return window.matchMedia("(prefers-reduced-motion: reduce)").matches;
  }

  function render(p: number): void {
    lastPRef.current = p;
    const rotY = (p * 360 * ROT_TURNS) % 360;
    const shrink = 1 - p;
    const sphere = sphereRef.current;
    if (sphere) sphere.style.transform = "rotateY(" + rotY + "deg) rotateX(14deg)";
    const pts = ptsRef.current;
    for (let i = 0; i < POINT_COUNT; i++) {
      const el = pts[i];
      if (!el) continue;
      const [bx, by, bz] = BASE[i];
      const x = bx * shrink, y = by * shrink, z = bz * shrink;
      el.style.transform = "translate3d(" + x + "px," + y + "px," + z + "px)";
    }
    if (pctRef.current) pctRef.current.textContent = Math.round(p * 100) + "%";
  }

  function togglePause(): void {
    pausedRef.current = !pausedRef.current;
    const root = rootRef.current;
    if (root) root.classList.toggle("is-paused", pausedRef.current);
    render(reduced() ? REDUCE_P : lastPRef.current);
  }

  function restart(): void {
    t0Ref.current = performance.now();
    render(reduced() ? REDUCE_P : 0);
  }

  function onKey(e: KeyEvt): void {
    if (e.key === " " || e.key === "Enter") { e.preventDefault(); togglePause(); }
    else if (e.key === "r" || e.key === "R") { e.preventDefault(); restart(); }
  }

  function onClick(): void {
    togglePause();
  }

  function onResize(): void {
    if (pausedRef.current || reduced()) render(reduced() ? REDUCE_P : lastPRef.current);
  }

  function frame(now: number): void {
    if (!pausedRef.current) {
      const t = (now - t0Ref.current) / 1000;
      render((t % LOOP) / LOOP);
    }
    rafRef.current = requestAnimationFrame(frame);
  }

  useEffect(() => {
    t0Ref.current = performance.now();
    window.addEventListener("resize", onResize);
    if (reduced()) {
      const root = rootRef.current;
      if (root) root.classList.add("is-still");
      render(REDUCE_P);
    } else {
      rafRef.current = requestAnimationFrame(frame);
    }
    return () => {
      window.removeEventListener("resize", onResize);
      cancelAnimationFrame(rafRef.current);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={styles.root} ref={rootRef} style={vars}>
        <p className={styles.hint}>클릭하거나 스페이스바를 누르면 멈추거나 다시 갑니다</p>
        <div
          className={styles.field}
          ref={fieldRef}
          role="application"
          aria-label={FIELD_LABEL}
          tabIndex={0}
          onClick={onClick}
          onKeyDown={onKey}
        >
          <div className={styles.scene}>
            <div className={styles.sphere} ref={sphereRef}>
              {BASE.map((_, i) => (
                <div key={i} className={styles.pt} ref={(el: HTMLDivElement | null) => { ptsRef.current[i] = el; }} />
              ))}
            </div>
          </div>
          <b className={styles.badge} aria-hidden="true"><span className={styles.badgeNum} ref={pctRef}>0%</span><span className={styles.badgeUnit}>진행</span></b>
        </div>
      </div>
    </main>
  );
}