html {
    box-sizing: border-box;
}
*, *:before, *:after {
    box-sizing: inherit;
}

*::before, *::after {
    content: "";
    display: table;
    clear: both;
}

html,body {
    font-family: Verdana, Geneva, Tahoma, sans-serif;
    font-size: 15px;
    line-height: 1.5;
    color: #000;
    background-color: #ffffff;
}

body {
    margin-top: 0;
}

section {
    background-color: #fff;
    color: #000;
    box-shadow: 0 2px 5px 0 rgba(0,0,0,0.16),0 2px 10px 0 rgba(0,0,0,0.12);
    padding: 16px;
    border-radius: 0.5em;
    margin: 8px 8px 16px 8px;
}

article {
    padding: 4px;
    margin: 4px;
    border-radius: 0.5em;
}

h1, h2, h3 {
    text-align: center;
}

nav {
    background-color: #fff;
    color: #000;
    box-shadow: 0 2px 5px 0 rgba(0,0,0,0.16);
    margin: 0px 0px 16px 0px;
    border-bottom-left-radius: 0.5em;
    border-bottom-right-radius: 0.5em;
}


.underline {
    border-bottom: 1px solid #d0d0d0;
}

nav a {
    display: inline-block;
    padding: 8px 16px;
    vertical-align: middle;
    overflow: hidden;
    text-align: center;
    text-decoration: none;
    white-space: nowrap;
    background-color: #206E32;
    color: #fff;
    border-bottom-left-radius: 0.5em;
    border-bottom-right-radius: 0.5em;
}

main {
    margin-left: auto;
    margin-right: auto;
    max-width: 1200px;
}

.container-half {
    padding: 8px;
    width: 48%;
    margin: 1%;
    float: left;
    box-sizing: inherit;
    text-align: center;
    min-height: 200px;
}

.container-third {
    padding: 8px;
    width: 31.33333%;
    margin: 1%;
    float: left;
    box-sizing: inherit;
    text-align: center;
    min-height: 200px;
}

.card {
    border: 1px solid #adadad8a;
    box-shadow: 4px 4px 4px 4px rgba(0, 0, 0, 0.062);
}

.center {
   margin-left: auto;
   margin-right: auto; 
}

table {
    border: 1px solid #ccc;
    border-collapse: collapse;
    border-spacing: 0;
    width: 100%;
    display: table;
}

thead {
    color:#fff;
    background-color: #206E32;
}

th {
    padding: 8px 8px 8px 16px;
    display: table-cell;
    text-align: center;
    vertical-align: bottom;
}

td {
    text-align: center;
}

.btn-operator {
    width: 100%;
}

.calc-input {
    height: 25px;
    width: 80%;
    font-family: monospace;
    font-size: 24px;
}

#ex2Demo {
    width: 250px; 
    height: 80px; 
    background: yellow;
    margin: auto;
}

.example-group {
    position: relative;
    display: inline-block;
  }

  .example-input {
    border-color: crimson;
    padding: 8px;
    border-radius: 5px;
  }

  .input-label {
    background-color: white;
    color: crimson;
    font-size: 11px;
    position: absolute;
    left: 25px;
    top: -7px;
    padding: 0 2px;
  }