02Tail direction switch

<main class="stage">
  <div class="bubble is-demo">
    See you soon
    <i class="tail tail--left"></i>
    <i class="tail tail--right"></i>
  </div>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────────
$duration: $dur-base;      // 왼쪽 ↔ 오른쪽 한 번 전환에 걸리는 시간
$easing: $ease-out;
$color: $subject-ink;      // 말풍선 색 (yellow 무대라 ink)

@include stage($stage-yellow);

.bubble {
  position: relative;
  padding: 14px 20px;
  border-radius: $r-card;
  background: $color;
  color: #fff;
  font-weight: 600; font-size: clamp(14px, 4.5vw, 17px); line-height: 1.4; font-family: inherit;

  &.is-demo {
    animation: tail-shift-loop $dur-loop $easing infinite;
  }
}

// clip-path 삼각형 꼬리 — 왼쪽·오른쪽 두 장을 겹쳐 두고 opacity 로만 바꿔친다
.tail {
  position: absolute;
  bottom: 10px;
  width: 14px;
  height: 14px;
  background: $color;
}
.tail--left  { left: -6px;  clip-path: polygon(100% 0, 100% 100%, 0 50%); animation: tail-left-loop $dur-loop $easing infinite; }
.tail--right { right: -6px; clip-path: polygon(0 0, 0 100%, 100% 50%);   animation: tail-right-loop $dur-loop $easing infinite; }

// 말풍선 전체가 왼쪽(수신)↔오른쪽(발신)으로 옮겨가고, 꼬리는 그 자리에서 opacity 로 바뀐다
@keyframes tail-shift-loop {
  0%   { transform: translateX(-70px); }
  32%  { transform: translateX(-70px); }
  68%  { transform: translateX(70px); }
  100% { transform: translateX(70px); }
}
@keyframes tail-left-loop {
  0%   { opacity: 1; }
  32%  { opacity: 1; }
  68%  { opacity: 0; }
  100% { opacity: 0; }
}
@keyframes tail-right-loop {
  0%   { opacity: 0; }
  32%  { opacity: 0; }
  68%  { opacity: 1; }
  100% { opacity: 1; }
}

@media (prefers-reduced-motion: reduce) {
  .bubble.is-demo, .tail--left, .tail--right { animation: none !important; }
  .bubble.is-demo { transform: translateX(-70px); }
  .tail--left { opacity: 1; }
  .tail--right { opacity: 0; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffd23f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.bubble {
  position: relative;
  padding: 14px 20px;
  border-radius: 16px;
  background: #17141a;
  color: #fff;
  font-weight: 600;
  font-size: clamp(14px, 4.5vw, 17px);
  line-height: 1.4;
  font-family: inherit;
}
.bubble.is-demo {
  animation: tail-shift-loop 2s ease-out infinite;
}

.tail {
  position: absolute;
  bottom: 10px;
  width: 14px;
  height: 14px;
  background: #17141a;
}

.tail--left {
  left: -6px;
  clip-path: polygon(100% 0, 100% 100%, 0 50%);
  animation: tail-left-loop 2s ease-out infinite;
}

.tail--right {
  right: -6px;
  clip-path: polygon(0 0, 0 100%, 100% 50%);
  animation: tail-right-loop 2s ease-out infinite;
}

@keyframes tail-shift-loop {
  0% {
    transform: translateX(-70px);
  }
  32% {
    transform: translateX(-70px);
  }
  68% {
    transform: translateX(70px);
  }
  100% {
    transform: translateX(70px);
  }
}
@keyframes tail-left-loop {
  0% {
    opacity: 1;
  }
  32% {
    opacity: 1;
  }
  68% {
    opacity: 0;
  }
  100% {
    opacity: 0;
  }
}
@keyframes tail-right-loop {
  0% {
    opacity: 0;
  }
  32% {
    opacity: 0;
  }
  68% {
    opacity: 1;
  }
  100% {
    opacity: 1;
  }
}
@media (prefers-reduced-motion: reduce) {
  .bubble.is-demo, .tail--left, .tail--right {
    animation: none !important;
  }
  .bubble.is-demo {
    transform: translateX(-70px);
  }
  .tail--left {
    opacity: 1;
  }
  .tail--right {
    opacity: 0;
  }
}

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

export type TailDirectionProps = {
  children: string;
  /** 발신(right)인가 수신(left)인가 */
  side?: "left" | "right";
  /** 전환에 걸리는 시간 (기본 300ms) */
  duration?: number;
  easing?: string;
  className?: string;
};

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

export default function TailDirection({
  children,
  side = "right",
  duration = 300,
  easing = "ease-out",
  className = "",
}: TailDirectionProps) {
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing };

  return (
    <div className={`${styles.bubble} ${styles[side]} ${className}`} style={vars}>
      {children}
      <i className={`${styles.tail} ${styles.tailLeft}`} />
      <i className={`${styles.tail} ${styles.tailRight}`} />
    </div>
  );
}