* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
.example {
    margin: 0 auto;
    text-align: center;
}

html {
    font-family: 'Nunito', sans-serif;
    font-size: 22px;
    font-weight: 400;
    color: #ffffff;
}

h1, h2, h3, p {
    color: #000000;
    transition: 0.5s;
}

h2 {
    margin-top: 60px;
    margin-bottom: 20px;
}

h3 {
    margin-top: 50px;
}

main {
    width: 240px;
    background-color: #5C5757;
    border: 1px solid #5C5757;
    border-radius: 5px;
    border: 1px solid #5C5757;
    box-shadow: 0 10px 30px 2px rgba(0, 0, 0, 0.50);
    margin: 60px auto;
}

.display {
    height: 90px;
    overflow: hidden;
    border-bottom: 3px solid #219A90;
    text-align: right;
    font-weight: 200;
    padding: 10px 10px 0 5px;
}

.small {
    overflow: hidden;
    font-size: 0.7rem;
    color: #79f8e7;
}

.big {
    overflow: hidden;
    font-size: 1.8rem;
    color: #ffffff;
    margin-top: 10px;
}

.keyboard {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr 1fr;
    grid-gap: 1px;
}

.button {
    height: 40px;
    background-color: #94A4A3;
    text-align: center;
    padding-top: 5px;
    transition: 0.5s;
    cursor: pointer;
}

.button:hover {
    background-color: #94bbb8;
}

.dark-operator {
    background-color: #687676;
}

.dark-operator:hover {
    background-color: #719e9b;
}

.light-operator {
    background-color: #D0E9E2;
    color: #000000;
}

.light-operator:hover {
    background-color: #a5c5bd;
}


.radius {
    border-radius: 0 0 5px 0;
}

/*
The zero button is double the size and have a
radius on the lower left corner
*/

.zero {
    grid-column: span 2;
    border-radius: 0 0 0 5px;
}

@media (max-width: 600px) {
    header .mini {
        display: flex;
        align-items: center;
        max-width: 100px;
        flex-direction: column;
    }
    .mini select {
        height: 30px;
        width: auto;
        margin-top: 10px;
        margin-bottom: 10px;
    }
    .mini input {
        width: auto;
        height: 30px;
        font-size: 1rem;
    }
    .mini button {
        width: auto;
        margin-top: 10px;
    }
}