* {
    box-sizing: border-box;
    transition-duration: .2s;
}

body {
    font-family: Verdana, Geneva, Tahoma, sans-serif;
    font-size: 12px;
}

header {
    text-align: center;
    margin: 35px 0 20px;
}

table {
    width: 100%;
    text-align: center;
}

th, td {
    padding: .25rem;
    margin: 0;
}

th {
    background-color: #2f2f2f;
    color: lightgrey;
}

button {
    background-color: #2f2f2f;
    color: lightgrey;
    border: none;
    border-radius: 15px;
    padding: .45rem;
    margin: .25rem 0 .8rem;
    font-weight: bolder;
    letter-spacing: .15rem;
    width: 100%;
}

button:hover {
    background-color: lightgrey;
    color: black;
    cursor: pointer;
}

#exampleSubnetMask {
    color: grey;
    font-weight: bold;
    letter-spacing: .12rem;
}

input, select {
    border-radius: 15px;
    border: none;
    background-color: lightgrey;
    padding: .5rem;
    margin-bottom: .2rem;
    letter-spacing: .2rem;
}

.formGroup {
    display: flex;
    justify-content: space-evenly;
    align-items: center;
}