*{
    padding: 0;
    margin: 0;
    box-sizing: border-box;
}
:root {
    --calc-background: #ffffff;
    --border-color: #D1E8F0;
    --main-color: #097790;
    --sec-color: #0B94A9;
}
body{
    min-height: 100vh;
    padding: 15px;
    background-color: #D6E3F7;
    position: relative;
}
.calculator {
    width: 100%;
    max-width: 350px;
    padding: 20px;
    background-color: var(--calc-background);
    border-radius: 15px;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%,-50%);
}
input {
    border: none;
    outline: none;
    cursor: pointer;
    padding: 10px;
    background-color: var(--calc-background);
    border-radius: 15px;
    color: var(--text-color);
    font-size: 15px;
    font-weight: 500;
    box-shadow: -5px -5px 15px rgba(0, 0, 0, 0.1), 5px 5px 15px rgba(0, 0, 0, 0.1);
    border:1px solid var(--border-color)
}
input:not(#display):active {
    transform: scale(0.85);
}
.display{
    margin-bottom: 15px;
}
.display input {
    width: 100%;
    padding:20px 15px;
    text-align: right;
    cursor:auto;
    box-shadow: 0 2px 8px #0001;
    border-radius: 10px;
    font-size: 20px;
    color: var(--text-color);
}
.keys {
    display: grid;
    grid-template-columns: repeat(4,1fr);
    grid-gap: 15px;
}
.operation {
    background: linear-gradient(135deg, var(--main-color) 60%, var(--sec-color) 100%);
    color: #fff;
    font-weight: bold;
}
.operation:hover {
    background: linear-gradient(135deg, var(--sec-color) 60%, var(--main-color) 100%);
}
.equal{
    grid-row: span 2;
}
.zero{
    grid-column: span 2;
}