06Cố định header + cột đầu

<main class="stage">
  <div class="freeze-wrap is-demo" tabindex="0" aria-label="Bảng so sánh giá. Cuộn bằng phím mũi tên hoặc kéo">
    <table class="freeze-table">
      <thead>
        <tr>
          <th class="freeze-table__corner">Gói</th>
          <th>Th1</th><th>Th2</th><th>Th3</th><th>Th4</th>
        </tr>
      </thead>
      <tbody>
        <tr><th scope="row">Cơ bản</th><td>9,900</td><td>9,900</td><td>9,900</td><td>9,900</td></tr>
        <tr><th scope="row">Pro</th><td>19,900</td><td>19,900</td><td>19,900</td><td>19,900</td></tr>
        <tr><th scope="row">Nhóm</th><td>39,900</td><td>39,900</td><td>39,900</td><td>39,900</td></tr>
        <tr><th scope="row">Doanh nghiệp</th><td>Liên hệ</td><td>Liên hệ</td><td>Liên hệ</td><td>Liên hệ</td></tr>
      </tbody>
    </table>
  </div>
</main>

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

$duration: $dur-base;                                  // 스크롤 자동 시연 왕복 시간(스크립트 값과 맞춤)
$easing: $ease-out;
$color: $subject-blue;                                 // 헤더·첫 열 배경

@include stage($stage-yellow);

.freeze-wrap {
  width: 220px;
  height: 132px;
  overflow: auto;
  border-radius: $r-card;
  background: $stage-paper;
  box-shadow: $shadow-raised;
}
.freeze-wrap:focus-visible { outline: 2px solid $stage-ink; outline-offset: 2px; }

.freeze-table {
  border-collapse: separate;
  border-spacing: 0;
  font-size: 12px;
  color: $stage-ink;
}
.freeze-table th, .freeze-table td {
  padding: $sp-2 $sp-3;
  min-width: 72px;
  white-space: nowrap;
  text-align: right;
  background: $stage-paper;
}
// 스티키 셀은 스크롤되는 내용 위로 겹쳐 그려지므로 배경이 완전 불투명해야 한다.
// rgba(..., .16) 처럼 반투명으로 두면 아래로 스크롤되는 글자가 비쳐 보여 겹침(고스팅)이 생긴다 — 실측으로 확인
.freeze-table thead th {
  position: sticky;
  top: 0;
  z-index: 2;
  background: #dee8fe;                 // $subject-blue 를 흰 배경에 16% 섞은 불투명 값
  text-align: right;
  font-weight: 700;
}
.freeze-table tbody th[scope="row"] {
  position: sticky;
  left: 0;
  z-index: 1;
  text-align: left;
  font-weight: 700;
  background: $stage-paper;
}
.freeze-table__corner {
  position: sticky;
  top: 0;
  left: 0;
  z-index: 3;
  text-align: left !important;
  background: #c5d6fc !important;      // $subject-blue 를 28% 섞은 불투명 값
}
// 여기도 th[scope="row"]는 스티키(왼쪽 고정)라 불투명해야 한다 — td는 스크롤에 그냥 같이 움직이니 상관없다
.freeze-table tbody tr:nth-child(even) td { background: rgba(23, 20, 26, .04); }
.freeze-table tbody tr:nth-child(even) th[scope="row"] { background: #f6f6f6; }

@media (prefers-reduced-motion: reduce) {
  .freeze-wrap { scroll-behavior: auto; }
}

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);
}

.freeze-wrap {
  width: 220px;
  height: 132px;
  overflow: auto;
  border-radius: 16px;
  background: #ffffff;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
}

.freeze-wrap:focus-visible {
  outline: 2px solid #17141a;
  outline-offset: 2px;
}

.freeze-table {
  border-collapse: separate;
  border-spacing: 0;
  font-size: 12px;
  color: #17141a;
}

.freeze-table th, .freeze-table td {
  padding: 8px 12px;
  min-width: 72px;
  white-space: nowrap;
  text-align: right;
  background: #ffffff;
}

.freeze-table thead th {
  position: sticky;
  top: 0;
  z-index: 2;
  background: #dee8fe;
  text-align: right;
  font-weight: 700;
}

.freeze-table tbody th[scope=row] {
  position: sticky;
  left: 0;
  z-index: 1;
  text-align: left;
  font-weight: 700;
  background: #ffffff;
}

.freeze-table__corner {
  position: sticky;
  top: 0;
  left: 0;
  z-index: 3;
  text-align: left !important;
  background: #c5d6fc !important;
}

.freeze-table tbody tr:nth-child(even) td {
  background: rgba(23, 20, 26, 0.04);
}

.freeze-table tbody tr:nth-child(even) th[scope=row] {
  background: #f6f6f6;
}

@media (prefers-reduced-motion: reduce) {
  .freeze-wrap {
    scroll-behavior: auto;
  }
}

(function () {
  var wrap = document.querySelector('.freeze-wrap');
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var raf = null, t0 = null;
  function maxX() { return wrap.scrollWidth - wrap.clientWidth; }
  function maxY() { return wrap.scrollHeight - wrap.clientHeight; }
  function loop(ts) {
    if (!wrap.classList.contains('is-demo')) return;
    if (t0 === null) t0 = ts;
    var p = ((ts - t0) / 2000) % 1;
    var s = p < .5 ? p * 2 : 2 - p * 2;
    wrap.scrollLeft = s * maxX();
    wrap.scrollTop = s * maxY();
    raf = requestAnimationFrame(loop);
  }
  function stop() {
    wrap.classList.remove('is-demo');
    if (raf) cancelAnimationFrame(raf);
  }
  wrap.addEventListener('pointerdown', stop);
  wrap.addEventListener('wheel', stop, { passive: true });
  wrap.addEventListener('keydown', function (e) {
    var step = 24;
    if (e.key === 'ArrowRight') { stop(); wrap.scrollLeft += step; }
    else if (e.key === 'ArrowLeft') { stop(); wrap.scrollLeft -= step; }
    else if (e.key === 'ArrowDown') { stop(); wrap.scrollTop += step; }
    else if (e.key === 'ArrowUp') { stop(); wrap.scrollTop -= step; }
    else return;
    e.preventDefault();
  });
  if (!reduce) requestAnimationFrame(loop);
})();

import { useRef, type CSSProperties } from "react";
import styles from "./StickyHeaderColumnFreeze.module.scss";

export type StickyHeaderColumnFreezeProps = {
  columns: string[];
  rows: { label: string; values: string[] }[];
  /** 헤더·첫 열 배경 색 */
  color?: string;
};

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

export default function StickyHeaderColumnFreeze({ columns, rows, color = "#2f6df6" }: StickyHeaderColumnFreezeProps) {
  const wrap = useRef<HTMLDivElement | null>(null);
  const vars: Vars = { "--color": color };

  const key = (e: any) => {
    const el = wrap.current;
    if (!el) return;
    const step = 24;
    if (e.key === "ArrowRight") { e.preventDefault(); el.scrollLeft += step; }
    else if (e.key === "ArrowLeft") { e.preventDefault(); el.scrollLeft -= step; }
    else if (e.key === "ArrowDown") { e.preventDefault(); el.scrollTop += step; }
    else if (e.key === "ArrowUp") { e.preventDefault(); el.scrollTop -= step; }
  };

  return (
    <div
      className={styles.wrap}
      style={vars}
      ref={wrap}
      tabIndex={0}
      aria-label="가격 비교표. 화살표 키나 드래그로 스크롤"
      onKeyDown={key}
    >
      <table className={styles.table}>
        <thead>
          <tr>
            <th className={styles.corner}>플랜</th>
            {columns.map((c) => <th key={c}>{c}</th>)}
          </tr>
        </thead>
        <tbody>
          {rows.map((r) => (
            <tr key={r.label}>
              <th scope="row">{r.label}</th>
              {r.values.map((v, i) => <td key={i}>{v}</td>)}
            </tr>
          ))}
        </tbody>
      </table>
    </div>
  );
}