* {
   box-sizing: border-box;
}

body {
   font-family: sans-serif;
}

nav {
   background-color: cyan;
   padding: 5px;
   position: sticky;
   top: 0;
}

.nav-bar {
   width: 100%;
   overflow: hidden
}

.nav-bar .nav-bar-item {
   padding: 8px 16px;
   float: left;
   width: auto;
   border: none;
   display: block;
   outline: 0
}

.nav-button {
   border: none;
   display: inline-block;
   padding: 8px 16px;
   vertical-align: middle;
   overflow: hidden;
   text-decoration: none;
   color: black;
   background-color: inherit;
   text-align: center;
   cursor: pointer;
   white-space: nowrap
}

.flex-container-column {
   display: flex;
   /* properti pendukung */
   flex-direction: column;
   max-width: 800px;
   margin: 0 auto;
   text-align: left;
}

.flex-container-column-header {
   display: flex;
   /* properti pendukung */
   flex-direction: column;
   margin: 0 auto;
   text-align: left;
   background-color: red;
   color: white;
}

.flex-container-column-footer {
   display: flex;
   /* properti pendukung */
   flex-direction: column;
   margin: 0 auto;
   text-align: center;
   color: red;
}

.flex-container-row {
   display: flex;
}

.button {
   flex-basis: 25%;
   /* properti pendukung */
   font-size: 1.5em;
   text-align: center;
   padding: 40px;
   border: 1px solid black;
   background: -webkit-linear-gradient(top, #d2d2d2, #ddd);
   cursor: pointer;
}

.double {
   flex-basis: 50%;
}

.display {
   color: white;
   width: 100%;
   padding: 10px 20px;
   background-color: #333333;
   border: 1px solid black;
   font-size: 2em;
}

.operator,
.negative,
.equals {
   background: orange;
}

.card {
   box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2);
   border-radius: 5px;
   padding: 30px;
   margin-top: 20px;
}

.button:hover {
   font-weight: bold;
}

.history {
   width: 80%;
   margin: 30px auto 0 auto;
   overflow: scroll;
}

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

th,
td {
   text-align: center;
   padding: 16px;
}

th {
   background-color: orange;
   color: white;
}

tr:nth-child(even) {
   background-color: #d2d2d2;
}

@media screen and (max-width: 513px) {
   .button {
      padding: 10px;
   }

   .history {
      width: 100%;
   }
}