.bd-placeholder-img {
    font-size: 1.125rem;
    text-anchor: middle;
    -webkit-user-select: none;
    -moz-user-select: none;
    user-select: none;
  }

  .nav-item button {
    margin: 2px 0;  /* 上下に2pxのマージンを設定 */
  }

  body {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    background-color: #f7f7f7;
  }

  header, footer {
    flex-shrink: 0;
  }

  main {
    flex: 1 0 auto;
  }