08Corner brackets closing in

<main class="stage">
  <button class="brk is-demo" type="button">
    <span class="brk__c brk__c--tl" aria-hidden="true"></span>
    <span class="brk__c brk__c--tr" aria-hidden="true"></span>
    <span class="brk__c brk__c--bl" aria-hidden="true"></span>
    <span class="brk__c brk__c--br" aria-hidden="true"></span>
    <span class="brk__label">Open settings</span>
  </button>
</main>

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

// 변형은 이 세 줄만 바꾼다
$duration: $dur-loop;
$easing:   $ease-spring;
$color:    $subject-cream;

@include stage($stage-ink);

.brk {
  position: relative;
  border: 0;
  cursor: pointer;
  padding: $sp-4 $sp-8;
  border-radius: 0;
  background: transparent;
  color: $color;
  font-family: inherit;
  font-size: clamp(16px, 5vw, 21px);
  font-weight: 700;
}

// 조각 넷은 같은 크기·같은 이동 거리. 다른 건 어느 쪽 변을 지우느냐뿐이다
.brk__c {
  position: absolute;
  width: 22px;
  height: 22px;
  border: 3px solid $color;
  --tx: -18px;
  --ty: -18px;
}

.brk__c--tl { top: -8px;    left: -8px;  border-right: 0; border-bottom: 0; --i: 0; }
.brk__c--tr { top: -8px;    right: -8px; border-left: 0;  border-bottom: 0; --tx: 18px;  --i: 1; }
.brk__c--bl { bottom: -8px; left: -8px;  border-right: 0; border-top: 0;    --ty: 18px;  --i: 2; }
.brk__c--br { bottom: -8px; right: -8px; border-left: 0;  border-top: 0;    --tx: 18px; --ty: 18px; --i: 3; }

.brk.is-demo .brk__c {
  animation: brk-close $duration $easing infinite;
  animation-delay: calc(var(--i) * 60ms);
}

// 모였다가 다시 흩어져 시작 위치로 돌아온다. 모인 상태에서 끝내면 매 바퀴 조각이 순간이동한다
@keyframes brk-close {
  0%       { translate: var(--tx) var(--ty); opacity: 0; }
  38%, 66% { translate: 0 0;                 opacity: 1; }
  100%     { translate: var(--tx) var(--ty); opacity: 0; }
}

// 키보드 포커스에도 같은 조준선
.brk:focus-visible {
  outline: none;
  .brk__c { animation: none; translate: 0 0; opacity: 1; }
}

@media (prefers-reduced-motion: reduce) {
  .brk.is-demo .brk__c { animation: none; translate: 0 0; opacity: 1; }
}

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);
}

.brk {
  position: relative;
  border: 0;
  cursor: pointer;
  padding: 16px 32px;
  border-radius: 0;
  background: transparent;
  color: #fff7e6;
  font-family: inherit;
  font-size: clamp(16px, 5vw, 21px);
  font-weight: 700;
}

.brk__c {
  position: absolute;
  width: 22px;
  height: 22px;
  border: 3px solid #fff7e6;
  --tx: -18px;
  --ty: -18px;
}

.brk__c--tl {
  top: -8px;
  left: -8px;
  border-right: 0;
  border-bottom: 0;
  --i: 0;
}

.brk__c--tr {
  top: -8px;
  right: -8px;
  border-left: 0;
  border-bottom: 0;
  --tx: 18px;
  --i: 1;
}

.brk__c--bl {
  bottom: -8px;
  left: -8px;
  border-right: 0;
  border-top: 0;
  --ty: 18px;
  --i: 2;
}

.brk__c--br {
  bottom: -8px;
  right: -8px;
  border-left: 0;
  border-top: 0;
  --tx: 18px;
  --ty: 18px;
  --i: 3;
}

.brk.is-demo .brk__c {
  animation: brk-close 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
  animation-delay: calc(var(--i) * 60ms);
}

@keyframes brk-close {
  0% {
    translate: var(--tx) var(--ty);
    opacity: 0;
  }
  38%, 66% {
    translate: 0 0;
    opacity: 1;
  }
  100% {
    translate: var(--tx) var(--ty);
    opacity: 0;
  }
}
.brk:focus-visible {
  outline: none;
}
.brk:focus-visible .brk__c {
  animation: none;
  translate: 0 0;
  opacity: 1;
}

@media (prefers-reduced-motion: reduce) {
  .brk.is-demo .brk__c {
    animation: none;
    translate: 0 0;
    opacity: 1;
  }
}

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

export type CornerBracketButtonProps = {
  label?: string;
  duration?: number;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };

const corners = ["tl", "tr", "bl", "br"] as const;

export default function CornerBracketButton({
  label = "Open settings",
  duration = 2000,
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#fff7e6",
}: CornerBracketButtonProps) {
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  return (
    <button type="button" className={styles.brk} style={vars}>
      {corners.map((c) => (
        <span key={c} className={`${styles.c} ${styles[c]}`} aria-hidden="true" />
      ))}
      <span className={styles.label}>{label}</span>
    </button>
  );
}