html, body {
    width: 100%;
    height: 100%;
    margin: 0px;
    border: 0;
    overflow: hidden;
    display: block;

    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    font-weight: lighter;
    background: #333;
    color: cyan;
    font-size: 12pt;
  }

  h1 {
      margin: 0;
      padding: 0;
  }

  canvas {
      position: absolute;
      top: 100px;
      left: 0;
      background-image:   url(../img/landscape.jpg);
      background-size:     cover;                      
      background-repeat:   no-repeat;
      background-position: center center;
  }
  
  .header {
    background: #222;
    height: 100px; 
    padding: 20px;
    display:  flex;
    justify-content: space-between;
  }

  .slider {
    -webkit-appearance: none;
    height: 25px;
    background: #444;
    outline: none;
    opacity: 0.7;
    -webkit-transition: .2s;
    transition: opacity .2s;
    display: block;
    margin-right: 10px;
    border-radius: 5px;
  }
  
  .slider:hover {
    opacity: 1;
  }
  
  .slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 25px;
    height: 25px;
    background:cyan;
    cursor: pointer;
    border: 0;
  }
  
  .slider::-moz-range-thumb {
    width: 25px;
    height: 25px;
    background: cyan;
    cursor: pointer;
    border: 0;
  }