.image-button {
  display: block;
  width: 200px; /* 画像の幅 */
  height: 150px; /* 画像の高さ */
  background-image: url("./image/first.jpg"); /* 通常時の画像 */
  background-size: cover;
}

.image-button:hover {
  background-image: url("./image/first2.jpg"); /* マウスが乗った時の画像 */
}

.visually-hidden {
  position: absolute;
  clip: rect(0 0 0 0);
  width: 1px;
  height: 1px;
  overflow: hidden;
}

 { box-sizing: border-box; }
  body {
    margin: 0;
    font-family: "Hiragino Kaku Gothic ProN", "Meiryo", sans-serif;
    background: #eee;
  }
  .reserve-banner {
    background: #0e3d54;
    color: #fff;
    padding: 30px 5%;
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    align-items: center;
    gap: 40px;
  }
  .reserve-banner .web-box {
    flex: 0 0 340px;
    max-width: 100%;
    background: #4d97cc;
    color: #fff;
    text-align: center;
    padding: 25px 15px;
    font-weight: bold;
    font-size: 1.05em;
    line-height: 1.5;
  }
  .reserve-banner .web-box .btn {
    display: inline-block;
    margin-top: 18px;
    border: 2px solid #fff;
    padding: 10px 30px;
    font-size: 0.95em;
    line-height: 1.4;
  }
  .reserve-banner .info {
    flex: 0 1 460px;
    max-width: 100%;
    font-weight: bold;
  }
  .reserve-banner .info p {
    margin: 0 0 6px 0;
    font-size: 1.1em;
  }
  .reserve-banner .info .clinic {
    margin-top: 28px;
    font-size: 1.15em;
  }
  @media (max-width: 600px) {
    .reserve-banner { text-align: center; }
    .reserve-banner .web-box { width: 100%; }
  }