02Border light runner

<main class="stage">
  <button class="glow" type="button">
    <span class="glow__ic" aria-hidden="true"><svg viewBox="0 0 256 256" width="20" height="20"><g fill="currentColor"><path d="m194.82 151.43l-55.09 20.3l-20.3 55.09a7.92 7.92 0 0 1-14.86 0l-20.3-55.09l-55.09-20.3a7.92 7.92 0 0 1 0-14.86l55.09-20.3l20.3-55.09a7.92 7.92 0 0 1 14.86 0l20.3 55.09l55.09 20.3a7.92 7.92 0 0 1 0 14.86" opacity=".2"/><path d="M197.58 129.06L146 110l-19-51.62a15.92 15.92 0 0 0-29.88 0L78 110l-51.62 19a15.92 15.92 0 0 0 0 29.88L78 178l19 51.62a15.92 15.92 0 0 0 29.88 0L146 178l51.62-19a15.92 15.92 0 0 0 0-29.88ZM137 164.22a8 8 0 0 0-4.74 4.74L112 223.85L91.78 169a8 8 0 0 0-4.78-4.78L32.15 144L87 123.78a8 8 0 0 0 4.78-4.78L112 64.15L132.22 119a8 8 0 0 0 4.74 4.74L191.85 144ZM144 40a8 8 0 0 1 8-8h16V16a8 8 0 0 1 16 0v16h16a8 8 0 0 1 0 16h-16v16a8 8 0 0 1-16 0V48h-16a8 8 0 0 1-8-8m104 48a8 8 0 0 1-8 8h-8v8a8 8 0 0 1-16 0v-8h-8a8 8 0 0 1 0-16h8v-8a8 8 0 0 1 16 0v8h8a8 8 0 0 1 8 8"/></g></svg></span>
    <span class="glow__label">Start free trial</span>
  </button>
</main>

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

// 변형은 이 세 줄만 바꾼다
$duration: $dur-loop;
$easing:   linear;
$color:    $subject-pink;

// 각도를 등록하지 않으면 conic-gradient 의 from 값이 보간되지 않아 러너가 아예 안 돈다
@property --angle {
  syntax: "<angle>";
  inherits: false;
  initial-value: 0deg;
}

@include stage($stage-ink);

.glow {
  position: relative;
  display: inline-flex;
  align-items: center;
  gap: $sp-2;
  border: 0;
  cursor: pointer;
  padding: $sp-4 $sp-8;
  border-radius: $r-pill;
  background: rgba($subject-cream, .06);
  color: $subject-cream;
  font-family: inherit;
  font-size: clamp(15px, 4.5vw, 19px);
  font-weight: 700;
}

// 테두리만 남기는 마스크: 바깥 사각형에서 content-box 를 빼면 테두리 굵기만 남는다
.glow::before {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: inherit;
  padding: $sp-1;
  background: conic-gradient(from var(--angle),
    rgba($color, 0) 0deg,
    rgba($color, 0) 232deg,
    rgba($color, 1) 300deg,
    rgba($color, .2) 330deg,
    rgba($color, 0) 360deg);
  -webkit-mask: linear-gradient(#fff 0 0) content-box, linear-gradient(#fff 0 0);
  -webkit-mask-composite: xor;
          mask-composite: exclude;
  animation: glow-run $duration $easing infinite;
}

.glow__ic { display: inline-flex; color: $color; }

// 0deg → 360deg 는 같은 그림이라 끝과 처음이 맞물린다. 340deg 에서 끊으면 매 바퀴 튄다
@keyframes glow-run {
  to { --angle: 360deg; }
}

@media (prefers-reduced-motion: reduce) {
  .glow::before { animation: none; background: rgba($color, .7); }
}

@property --angle {
  syntax: "<angle>";
  inherits: false;
  initial-value: 0deg;
}
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);
}

.glow {
  position: relative;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  border: 0;
  cursor: pointer;
  padding: 16px 32px;
  border-radius: 999px;
  background: rgba(255, 247, 230, 0.06);
  color: #fff7e6;
  font-family: inherit;
  font-size: clamp(15px, 4.5vw, 19px);
  font-weight: 700;
}

.glow::before {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: inherit;
  padding: 4px;
  background: conic-gradient(from var(--angle), rgba(255, 158, 187, 0) 0deg, rgba(255, 158, 187, 0) 232deg, #ff9ebb 300deg, rgba(255, 158, 187, 0.2) 330deg, rgba(255, 158, 187, 0) 360deg);
  -webkit-mask: linear-gradient(#fff 0 0) content-box, linear-gradient(#fff 0 0);
  -webkit-mask-composite: xor;
  mask-composite: exclude;
  animation: glow-run 2s linear infinite;
}

.glow__ic {
  display: inline-flex;
  color: #ff9ebb;
}

@keyframes glow-run {
  to {
    --angle: 360deg;
  }
}
@media (prefers-reduced-motion: reduce) {
  .glow::before {
    animation: none;
    background: rgba(255, 158, 187, 0.7);
  }
}

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

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

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

export default function GlowRunnerButton({
  label = "Start free trial",
  duration = 2000,
  easing = "linear",
  color = "#ff9ebb",
}: GlowRunnerButtonProps) {
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  return (
    <button type="button" className={styles.glow} style={vars}>
      <span className={styles.label}>{label}</span>
    </button>
  );
}