styles.scss

$level-color: lawngreen;

@mixin warn-highlight {
  padding: 0 .2em;
  background: gold;
}

@mixin title-default ( $mb: 0.83em ) {
  font-weight: normal;
  margin-top: 0;
  margin-bottom: $mb;
}

.gnr-html {
  font-size: 16px;
}

.gnr-body {
  min-width: 800px;
  margin: 0;
  background: #EEE;
  color: #000;
  font: 14px/1.5 Trebuchet MS, sans-serif;
}

A {
  color: royalblue;

  &:hover {
    text-decoration: none;
  }
}

UL, LI {
  padding: 0;
  margin: 0;
  list-style: none ;
}

.gnr-hidden {
  display: none;
}

.gnr-highlight {
  @include warn-highlight;
}

.gnr-page {
  margin: 2rem auto;
  padding: 3rem;
  width: 80%;
  min-width: 800px;
  max-width: 1200px;
  box-sizing: content-box;
  background: #FFF;
  box-shadow: 0 0 10px rgba(0,0,0,.2);
}
  .gnr-page__title {
    @include title-default( $mb: 1.5em );
    padding-bottom: 1rem;
    border-bottom: 3px solid #EEE;
    text-align: center;
    font-size: 2em;
  }

  .gnr-page__container {
    display: flex;
    justify-content: space-between;
  }
    .gnr-column {
      width: 48%;
    }
      .gnr-column__title {
        @include title-default;
        font-size: 1.5em;
      }

  .gnr-page__footer {
    margin-top: 3rem;
    padding-top: 1rem;
    border-top: 3px solid #EEE;

    display: flex;
    justify-content: space-between;
  }


/* Tree
------------------------------ */

.gnr-tree {
  min-height: 200px;
  padding: 1rem;
  box-sizing: border-box;
  border: 1px solid #DDD;
  display: flex;
  justify-content: center;
  align-items: center;
}
  .gnr-tree__placeholder {
    width: 80%;
    text-align: center;
    font-size: 14px;
    color: #999;
  }

/* Level
------------------------------ */

.gnr-level {
    position: relative;
    margin-bottom: .5rem;
    margin-left: 1.2rem;
    background:
      linear-gradient(to right,
        lawngreen 1px,
        transparent 1px);
    background-repeat: no-repeat;
    background-position: 10px 0;
  }
    .gnr-level:before {
      content: "";
      display: block;
      position: absolute;
      z-index: 0;
      bottom: 0;
      width: 2rem;
      margin-left: 10px;
      height: 10px;
      background: white;
      border-top: 1px solid $level-color;

    }
    .gnr-level--0:before {
      height: 10px;
    }
    .gnr-level__item {
      position: relative;

      &:before {
        content: "";
        display: block;
        position: absolute;
        width: .7rem;
        height: .08rem;
        margin-left: -.55rem;
        margin-top: .6rem;
        vertical-align: top;
        background: $level-color;
      }
      .gnr-level--0 > &:before {
        content: none;
      }
    }
      .gnr-elem {
          background: white;
          padding-left: .3rem;
      }
        .gnr-elem__tag {
          background: #FFF;
          color: royalblue;
        }

        .gnr-class__item {
          white-space: nowrap;
        }

/* Code I/O
------------------------------ */
.gnr-code-input {
  width: 100%;
  height: 200px;
  margin-bottom: 2rem;
  padding: 1rem;
  box-sizing: border-box;
  border: 1px solid #CCC;
  box-shadow: 0 0 10px rgba(0,0,0,.2) inset;
  font-size: inherit;
}
.gnr-code-output {
  display: none;
}

/* Deep
------------------------------ */

.gnr-deep__title {
  @include title-default;
  font-size: 1.17em;
}

.gnr-deep__digit {
  display: inline-block;
  font-weight: bold;
  color: crimson;
}

.gnr-deep__range {
  width: 100%;
  margin: 0;
  cursor: pointer;
}

/* Messages
------------------------------ */

.gnr-messages {
  margin-top: 2rem;
}

.gnr-message {
  padding: .75rem;
  background: lemonchiffon;
}

  .gnr-message:not(:last-child) {
    margin-bottom: .75rem;
  }

/* Headers list
------------------------------ */

.headers__list {
  margin: 0;
  display: flex;
  flex-wrap: wrap;
}
  .headers__item {
    margin-left: .5rem;

    &--notfound {
      opacity: .3;
    }
  }