html {
    font-size: 175%;
    font-weight: 300;
    line-height: 1.3;
}

body {
    align-items: center;
    background-image: linear-gradient(236deg, #74ebd5, #acb6e5);
    display: flex;
    height: 100vh;
    justify-content: center;
}

.calculator-keys {
    background-color: #999;
    display: grid;
    grid-gap: 1px;
    grid-template-columns: repeat(4, 1fr);
}

:root {
    font-family: Helvetica, Arial, sans-serif;
}

.calculator {
    border-radius: 12px;
    box-shadow: 0 0 40px 0px rgba(0, 0, 0, 0.15);
    margin-left: auto;
    margin-right: auto;
    margin-top: 2em;
    max-width: 15em;
    overflow: hidden;
}

.calculator-display {
    background-color: #222222;
    color: #fff;
    font-size: 1.7em;
    padding: 0.5em 0.75em;
    text-align: right;
}

button {
    border: 0;
    border-radius: 0;
    background-color: transparent;
    font-size: inherit;
    font-family: inherit;
    font-weight: inherit;
    cursor: pointer;
}

.calculator-keys>* {
    background-color: #fff;
    padding: 0.5em 1.25em;
    position: relative;
    text-align: center;
}

.key-equal {
    background-image: linear-gradient(to bottom, #fe886a, #ff7033);
    grid-column: -2;
    grid-row: 2 / span 4;
}

.calculator-keys>*:active::before {
    background-color: rgba(0, 0, 0, 0.2);
    bottom: 0;
    box-shadow: 0 0 6px 0 rgba(0, 0, 0, 0.5) inset;
    content: "";
    left: 0;
    opacity: 0.3;
    position: absolute;
    right: 0;
    top: 0;
    z-index: 1;
}

button:hover{
    background-color: lightgray;
    transition: 0.5s;
}

@media (min-width:0px) and (max-width:600px) {
   .calculator{
    margin-top: -380px;
   }
}