.title {
    text-align: center;
}

.button {
    background-color: #4CAF50; /* Green */
    border: none;
    color: white;
    padding: 15px 32px;
    text-align: center;
    text-decoration: none;
    display: inline-block;
    font-size: 16px;
}

.button-green {background-color: #4CAF50;} /* Green */
.button-blue {background-color: #008CBA;} /* Blue */
.button-red {background-color: #f44336;} /* Red */
.button-gray {background-color: #e7e7e7; color: black;} /* Gray */
.button-black {background-color: #555555;} /* Black */

.center {
    margin: auto;
    width: 50%;
    //border: 3px solid green;
    padding: 10px;
}

tr:hover {background-color: #f5f5f5;}
th, td {
    padding: 15px;
    text-align: left;
}
table {
    border-collapse: collapse;
}

table, th, td {
    border: 1px solid black;
}