styles.css

body {font-family: 'Source Sans Pro', Raleway, sans-serif;     text-align: center;}
* {box-sizing: border-box}
textarea {
    font-family: Consolas, monospace; 
    background-color: #ffffff;
    font-family: consolas,"courier new",monospace;
    font-size: 15px;
    height: 100%;
    padding: 8px;
    resize: none;
    line-height: normal;
}

h1 {
    text-align: center;
}

.btn {
    background-color: dodgerblue;
    color: white;
    padding: 15px 20px;
    border: none;
    cursor: pointer;
    width: 100%;
    opacity: 0.9;
    font-family: inherit;
    font-size: 1em;
}

.btn:hover {
    opacity: 1;
}

.all {
    text-align: left;
}


input {
    -webkit-writing-mode: horizontal-tb !important;
    text-rendering: auto;
    color: -internal-light-dark(black, white);
    letter-spacing: normal;
    word-spacing: normal;
    text-transform: none;
    text-indent: 0px;
    text-shadow: none;
    display: inline-block;
    text-align: start;
    appearance: auto;
    background-color: -internal-light-dark(rgb(255, 255, 255), rgb(59, 59, 59));
    -webkit-rtl-ordering: logical;
    cursor: text;
    margin: 0em;
    font: 400 13.3333px Arial;
    padding: 1px 2px;
    border-width: 2px;
    border-style: inset;
    border-color: -internal-light-dark(rgb(118, 118, 118), rgb(133, 133, 133));
    border-image: initial;
    font-family: inherit;
}

/* Style the tab */
.tab {
  float: left;
  border: 1px solid #ccc;
  background-color: #f1f1f1;
  width: 30%;
  height: 300px;
}

/* Style the buttons inside the tab */
.tab button {
  display: block;
  background-color: inherit;
  color: black;
  padding: 22px 16px;
  width: 100%;
  border: none;
  outline: none;
  text-align: left;
  cursor: pointer;
  font-size: 17px;
}

/* Change background color of buttons on hover */
.tab button:hover {
  background-color: #ddd;
}

/* Create an active/current "tab button" class */
.tab button.active {
  background-color: #ccc;
}

/* Style the tab content */
.tabcontent {
  float: left;
  padding: 0px 12px;
  border: 1px solid #ccc;
  width: 70%;
  border-left: none;
  height: 300px;
  display: none;
}

/* Clear floats after the tab */
.clearfix::after {
  content: "";
  clear: both;
  display: table;
}


pre {
    background: #f4f4f4;
    border: 1px solid #ddd;
    border-left: 3px solid #f36d33;
    color: #666;
    page-break-inside: avoid;
    font-family: monospace;
    font-size: 15px;
    line-height: 1.6;
    margin-bottom: 1.6em;
    max-width: 100%;
    overflow: auto;
    padding: 1em 1.5em;
    display: block;
    word-wrap: break-word;
}




*.unselectable {
   -moz-user-select: -moz-none;
   -khtml-user-select: none;
   -webkit-user-select: none;

   /*
     Introduced in IE 10.
     See http://ie.microsoft.com/testdrive/HTML5/msUserSelect/
   */
   -ms-user-select: none;
   user-select: none;
}


textarea {
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;

    width: 100%;
}

br {
    -moz-user-select: -moz-none;
   -khtml-user-select: none;
   -webkit-user-select: none;

   /*
     Introduced in IE 10.
     See http://ie.microsoft.com/testdrive/HTML5/msUserSelect/
   */
   -ms-user-select: none;
   user-select: none;   
}