body {
    font-family: sans-serif;
  }
  
  /* ---- button ---- */
  
  .button {
    display: inline-block;
    position: relative;
    padding: 10px 18px;
    margin-bottom: 10px;
    background: #EEE;
    border: none;
    border-radius: 7px;
    background-image: linear-gradient( to bottom, hsla(0, 0%, 0%, 0), hsla(0, 0%, 0%, 0.2) );
    color: #222;
    font-family: sans-serif;
    font-size: 16px;
    text-shadow: 0 1px white;
    cursor: pointer;
  }
  
  .button:hover {
    text-shadow: 0 1px hsla(0, 0%, 100%, 0.5);
    

  }
  .button::after{
    content: "";
    position: absolute;
    width: 0%;
    left: 0;
    right: 0;
    margin: auto;
    background-color: #00F;
    height: 1px;
    bottom: 0;
    transition: all 0.5s;
  }
  .button:hover:after{
   width: 80%;

  }
 
  .is-checked::after {
    content: "";
    position: absolute;
    width: 80%;
    left: 0;
    right: 0;
    background-color: #00F;
    height: 1px;
    bottom: 0;
  }
  
  .button.is-checked {
    color: white;
    text-shadow: 0 -1px hsla(0, 0%, 0%, 0.8);
  }
  
  .button:active {
    box-shadow: inset 0 1px 10px hsla(0, 0%, 0%, 0.8);
  }
  
  /* ---- button-group ---- */
  
  .button-group:after {
    content: '';
    display: block;
    clear: both;
  }
  .button-group{
    margin: auto;
    width: fit-content;
  }
  .button-group .button {
    float: left;
    border-radius: 0;
    margin-left: 0;
    margin-right: 1px;
  }
  
  .button-group .button:first-child { border-radius: 0.5em 0 0 0.5em; }
  .button-group .button:last-child { border-radius: 0 0.5em 0.5em 0; }
  
  /* ---- isotope ---- */
  
  .grid {
    border: 1px solid #333;
  }
  
  /* clear fix */
  .grid:after {
    content: '';
    display: block;
    clear: both;
  }
  
  /* ---- .element-item ---- */
  
  .element-item {
    position: relative;
    float: left;
    padding: 5px;
    background: transparent;
    color: #262524;
  }
  
  .element-item > * {
    margin: 0;
    padding: 0;
  }
  
  .element-item .name {
    position: absolute;
  
    left: 10px;
    top: 60px;
    text-transform: none;
    letter-spacing: 0;
    font-size: 12px;
    font-weight: normal;
  }
  
  .element-item .symbol {
    position: absolute;
    left: 10px;
    top: 0px;
    font-size: 42px;
    font-weight: bold;
    color: white;
  }
  
  .element-item .number {
    position: absolute;
    right: 8px;
    top: 5px;
  }
  
  .element-item .weight {
    position: absolute;
    left: 10px;
    top: 76px;
    font-size: 12px;
  }
  img{
    width: 100%
  }
  .element-item.alkali          { background: #F00; background: hsl(   0, 100%, 50%); }
  .element-item.alkaline-earth  { background: #F80; background: hsl(  36, 100%, 50%); }
  .element-item.lanthanoid      { background: #FF0; background: hsl(  72, 100%, 50%); }
  .element-item.actinoid        { background: #0F0; background: hsl( 108, 100%, 50%); }
  .element-item.transition      { background: #0F8; background: hsl( 144, 100%, 50%); }
  .element-item.post-transition { background: #0FF; background: hsl( 180, 100%, 50%); }
  .element-item.metalloid       { background: #08F; background: hsl( 216, 100%, 50%); }
  .element-item.diatomic        { background: #00F; background: hsl( 252, 100%, 50%); }
  .element-item.halogen         { background: #F0F; background: hsl( 288, 100%, 50%); }
  .element-item.noble-gas       { background: #F08; background: hsl( 324, 100%, 50%); }
  
  .button-group span{
    background-color: transparent;
    color: #E6E6E6;
  }