05Placeholder trượt

<main class="stage">
  <div class="ps is-demo">
    <input id="ps-email" class="ps__input" type="email" placeholder=" " autocomplete="email">
    <span class="ps__ghost" aria-hidden="true">Nhập địa chỉ email</span>
    <span class="ps__bloom" aria-hidden="true"></span>
  </div>
</main>

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

// ── 변수 4개 ──────────────────────────────────────────
$duration: $dur-quick;                 // 가짜 플레이스홀더가 밀려나는 시간
$easing: cubic-bezier(.3, 1.6, .4, 1); // 스프링 오버슛 — 밀려나는 거리가 목표 10px 을 지나 13px 까지 뻗었다가 돌아온다
$color: $subject-blue;                 // 포커스 시 테두리 색

@include stage($stage-ink);

.ps { position: relative; width: min(240px, 82vw); }

.ps__input {
  box-sizing: border-box;
  width: 100%;
  border: 2px solid rgba($subject-cream, .35);
  border-radius: $r-control;
  padding: $sp-4 $sp-4;
  font-weight: 500;
  font-size: clamp(14px, 4vw, 16px);
  line-height: 1;
  font-family: inherit;
  color: $subject-cream;
  background: transparent;

  &:focus { outline: none; border-color: $color; }
}

// 포커스 순간 입력칸 중심에서 번지는 radial 글로우 확산 한 겹
.ps__bloom {
  position: absolute;
  inset: -6px;
  border-radius: calc(#{$r-control} + 6px);
  background: radial-gradient(circle, rgba($color, .3) 0%, rgba($color, 0) 70%);
  opacity: 0;
  pointer-events: none;
}
.ps__input:focus ~ .ps__bloom { animation: ps-bloom $dur-base $ease-out; }

@keyframes ps-bloom {
  0%   { opacity: 0; transform: scale(.65); }
  40%  { opacity: 1; transform: scale(1); }
  100% { opacity: 0; transform: scale(1.22); }
}

// 진짜 placeholder 는 빈 칸(" ") 이고, 보이는 문구는 이 span 이 대신 맡는다
.ps__ghost {
  position: absolute;
  left: $sp-4; top: 50%;
  transform: translate(0, -50%);
  color: rgba($subject-cream, .55);
  font-weight: 500;
  font-size: clamp(13px, 3.8vw, 15px);
  line-height: 1;
  font-family: inherit;
  pointer-events: none;
  transition: transform $dur-base $easing, opacity $duration $ease-out;
}

// 실사용: 포커스거나 값이 있으면(:not(:placeholder-shown)) 옆으로 밀리며 사라진다
.ps__input:focus ~ .ps__ghost,
.ps__input:not(:placeholder-shown) ~ .ps__ghost {
  transform: translate(13px, -50%) scale(.94);
  opacity: 0;
}

@media (prefers-reduced-motion: reduce) {
  .ps__ghost { transition: none; }
  .ps__input:focus ~ .ps__bloom { animation: 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);
}

.ps {
  position: relative;
  width: min(240px, 82vw);
}

.ps__input {
  box-sizing: border-box;
  width: 100%;
  border: 2px solid rgba(255, 247, 230, 0.35);
  border-radius: 12px;
  padding: 16px 16px;
  font-weight: 500;
  font-size: clamp(14px, 4vw, 16px);
  line-height: 1;
  font-family: inherit;
  color: #fff7e6;
  background: transparent;
}
.ps__input:focus {
  outline: none;
  border-color: #2f6df6;
}

.ps__bloom {
  position: absolute;
  inset: -6px;
  border-radius: calc(12px + 6px);
  background: radial-gradient(circle, rgba(47, 109, 246, 0.3) 0%, rgba(47, 109, 246, 0) 70%);
  opacity: 0;
  pointer-events: none;
}

.ps__input:focus ~ .ps__bloom {
  animation: ps-bloom 300ms ease-out;
}

@keyframes ps-bloom {
  0% {
    opacity: 0;
    transform: scale(0.65);
  }
  40% {
    opacity: 1;
    transform: scale(1);
  }
  100% {
    opacity: 0;
    transform: scale(1.22);
  }
}
.ps__ghost {
  position: absolute;
  left: 16px;
  top: 50%;
  transform: translate(0, -50%);
  color: rgba(255, 247, 230, 0.55);
  font-weight: 500;
  font-size: clamp(13px, 3.8vw, 15px);
  line-height: 1;
  font-family: inherit;
  pointer-events: none;
  transition: transform 300ms cubic-bezier(0.3, 1.6, 0.4, 1), opacity 220ms ease-out;
}

.ps__input:focus ~ .ps__ghost,
.ps__input:not(:placeholder-shown) ~ .ps__ghost {
  transform: translate(13px, -50%) scale(0.94);
  opacity: 0;
}

@media (prefers-reduced-motion: reduce) {
  .ps__ghost {
    transition: none;
  }
  .ps__input:focus ~ .ps__bloom {
    animation: none;
  }
}

// .is-demo 자동 재생: 진짜 focus 를 오가며 :focus·:placeholder-shown 을 그대로 탄다 (3줄)
var el = document.querySelector('.is-demo .ps__input');
var t = function () { document.activeElement === el ? el.blur() : el.focus({ preventScroll: true }); };  // preventScroll — iframe 안 포커스가 홈 그리드의 부모 스크롤을 끌어당기지 않게 (사용자 2026-09-10 실측)
t(); setInterval(t, 400);

import { useState } from "react";
import type { CSSProperties, ChangeEvent } from "react";
import styles from "./PlaceholderSlide.module.scss";

export type PlaceholderSlideProps = {
  ghost?: string;
  type?: string;
  duration?: number;
  easing?: string;
  color?: string;
};

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

export default function PlaceholderSlide({
  ghost = "Enter your email address",
  type = "email",
  duration = 220,
  easing = "ease-out",
  color = "#2f6df6",
}: PlaceholderSlideProps) {
  const [value, setValue] = useState("");
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  return (
    <div className={styles.ps} style={vars}>
      <input
        className={styles.input}
        type={type}
        placeholder=" "
        value={value}
        onChange={(e: ChangeEvent<HTMLInputElement>) => setValue(e.target.value)}
      />
      <span className={styles.ghost} aria-hidden="true">{ghost}</span>
      <span className={styles.bloom} aria-hidden="true" />
    </div>
  );
}