html {
    font-size: 62.5%;
    box-sizing: border-box;
    background: #121212;
}

*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: inherit;
}

.calculator {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 400px;
    padding: 40px;
    padding-top: 75px;
    background: black;
    border-radius: 25px;
    box-shadow: 10px 15px 10px purple;
}

.calculator-screen {
    font-family: 'Roboto Mono', monospace;
    font-weight: 400;
    width: 100%;
    font-size: 5rem;
    height: 80px;
    border: none;
    background: white;
    color: black;
    text-align: right;
    padding-right: 10px;
}

.calculator-buttons {
    display: flex;
    flex-direction: row;
    flex-wrap: wrap;
    padding: 15px;
    padding-bottom: 5px;
}

button {
    font-family: 'Roboto Mono', monospace;
    height: 60px;
    background: white;
    border: none;
    border-radius: 30px;
    font-size: 4rem;
    font-weight: 600;
    color: black;
    margin: 7px;
    padding: 2px 5px 5px 5px;
    flex: 1 0 18%;
}

.all-clear {
    background: purple;
    color: white;
    font-size: 3rem;
}

button:hover {
    background:#eaeaea67;
}