2026-css-anchor-positioning/anchor-basic.html at main · codegrid/2026-css-anchor-positioning · GitHub

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<!DOCTYPE html>
<html lang="ja">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <link rel="stylesheet" href="style.css">
  <title>anchor()関数でツールチップを配置する</title>
  <style>
    *, *::before, *::after {
      box-sizing: border-box;
    }

    body {
      margin: 0;
      font-family: sans-serif;
      min-height: 100vh;
      display: flex;
      align-items: center;
      justify-content: center;
      background-color: #f5f5f5;
    }

    @keyframes move-anchor {
      0%   { translate: 0px 0px; }
      25%  { translate: 120px 0px; }
      50%  { translate: 120px 80px; }
      75%  { translate: 0px 80px; }
      100% { translate: 0px 0px; }
    }

    .anchor {
      anchor-name: --my-anchor;
      width: fit-content;
      padding: 8px 16px;
      background-color: #1a73e8;
      color: #fff;
      border: none;
      border-radius: 4px;
      font-size: 1rem;
      cursor: pointer;
      animation: move-anchor 3s ease-in-out infinite paused;
    }

    .anchor.is-animated {
      animation-play-state: running;
    }

    .tooltip {
      position: absolute;
      position-anchor: --my-anchor;
      top: calc(anchor(bottom) + 8px);
      left: anchor(center);
      translate: -50% 0;
      padding: 8px 16px;
      background-color: #333;
      color: #fff;
      border-radius: 4px;
      white-space: nowrap;
    }

    /* 吹き出しの三角（上向き） */
    .tooltip::before {
      content: "";
      position: absolute;
      top: -6px;
      left: 50%;
      translate: -50% 0;
      border: 6px solid transparent;
      border-top: none;
      border-bottom-color: #333;
    }

    .control {
      position: fixed;
      bottom: 16px;
      left: 50%;
      translate: -50% 0;
      padding: 8px 16px;
      background-color: #fff;
      border: 1px solid #ccc;
      border-radius: 4px;
      font-size: 0.875rem;
      cursor: pointer;
    }
  </style>
</head>
<body>
  <button class="anchor" type="button">アンカー要素</button>
  <div class="tooltip">ツールチップのテキストが入ります</div>
  <button class="control" type="button" id="toggle-btn">アニメーション開始</button>

  <script>
    const anchor = document.querySelector('.anchor');
    const toggleBtn = document.getElementById('toggle-btn');

    toggleBtn.addEventListener('click', () => {
      anchor.classList.toggle('is-animated');
      toggleBtn.textContent = anchor.classList.contains('is-animated')
        ? 'アニメーション停止'
        : 'アニメーション開始';
    });
  </script>
</body>
</html>