@import "syntax-variables";

@font-family: "Helvetica Neue", Helvetica, sans-serif;
.api-blueprint-preview {
  font-family: @font-family;
  font-size: 14px;
  line-height: 1.6;
  background-color: #fff;
  overflow: scroll;
  box-sizing: border-box;
  padding: 20px;

  :not(.editor-colors) > code {
    color: #999;
    text-shadow: none;
  }

  h2 {
    font-size: 24px;
  }

  h3 {
    font-size: 20px;
  }

  a {
    color: #48f;
  }

  pre {
    margin-bottom: 15px;
  }

  .apib-action {
    margin: 15px 0;
    padding: 6px 8px;
    background-color: #ddd;
    border-radius: 3px;

    code {
      color: #666;
      text-shadow: none;
    }
  }
}

.api-blueprint-spinner {
  margin: auto;
  background-image: url(images/octocat-spinner-128.gif);
  background-repeat: no-repeat;
  background-size: 64px;
  background-position: top center;
  padding-top: 70px;
  text-align: center;
}

@import "syntax-variables";

@font-family: "Helvetica Neue", Helvetica, sans-serif;
.api-blueprint-preview {
  font-family: @font-family;
  font-size: 14px;
  line-height: 1.6;
  background-color: #fff;
  overflow: scroll;
  box-sizing: border-box;
  padding: 20px;

  :not(.editor-colors) > pre {
    background: #2E3239;
    color: #F8F8F2;
    text-shadow: none;
  }

  h2 {
    font-size: 24px;
  }

  h3 {
    font-size: 20px;
  }

  a {
    color: #48f;
  }

  pre {
    margin-bottom: 15px;
  }

  .apib-action {
    margin: 15px 0;
    padding: 6px 8px;
    background-color: #ddd;
    border-radius: 3px;

    code {
      color: #666;
      text-shadow: none;
    }
  }
}

.api-blueprint-spinner {
  margin: auto;
  background-image: url(images/octocat-spinner-128.gif);
  background-repeat: no-repeat;
  background-size: 64px;
  background-position: top center;
  padding-top: 70px;
  text-align: center;
}

Change "pre" background to match Monokai theme
Change "pre" background to match Monokai theme