body {
    display: flex;
    text-align: center;
    flex-direction: column;
    height: 100vh;
    margin: 0;
    background-color: rgb(9, 73, 9);
    color: #eee;
}

header {
    flex: 0 0 auto;
}

main {
    flex: 1;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

.calculator {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-template-rows: auto;
    grid-gap: 5px;
    background: #594859;
    padding: 10px;
    box-shadow: 1px 2px 10px 1px #222;
}

.display {
    grid-column: 1 / span 4;
    height: 100px;
    max-width: 415px;
    overflow: hidden;
    background: #eee;
    color: #111;
    text-align: right;
    display: flex;
    flex-direction: column;
}
.top-screen {
    height: 40%;
    font-size: 20px;
}
.main-screen {
    height: 60%;
    font-size: 50px;
}

button {
    height: 100px;
    width: 100px;
    font-size: 50px;
    border-color: #eee;
    box-shadow: 1px 2px 10px 1px #222;
}

button:hover {
    filter: brightness(.9);
}

.num {
    background: #d9e1f2;
}

.clear {
    grid-column: span 2;
    width: 205px;
    background: #f98383;
}

.operator {
    background: #ffff69;
}

.equal {
    background: #79ff54;
}

footer {
    flex: 0 0 auto;
}