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

body {
   font-size: 100%;
}

header {
   text-align: center;
   border-bottom: solid 0.2rem #136FFF;
}

article {
   max-width: 40em;
   margin-right: auto;
   margin-left: auto;
}

p {
   line-height: 1.8;
}

.center {
   text-align: center;
}

.shadebox {
   margin: 10px 0;
   width: 100%;
   padding: 5px 10px;
   box-shadow: 2px 2px 5px gray;
   border-radius: 10px;
   border: 1px solid gray;
}

.shadebox>:first-child{
   margin-top: 0;
}

.shadebox>:last-child{
   margin-bottom: 0;
}

.math.display {
   display: block;
   padding-left: 3em;
   padding-right: 3em;
   overflow-x: auto;
   overflow-y: hidden;

   margin-right: auto;
   margin-left: auto;
}

.math.inline {
   display: inline;
   padding-left: 0.2em;
   padding-right: 0.2em;
}