* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Courier New', Courier, monospace;
}

body {
    min-height: 100vh;
    background-color: #f7f7f7;
    display: flex;
    align-items: center;
    justify-content: center;
}

.container {
    background-color: #fff;
    max-width: 400px;
    width: 100%;
    height: 400px;
    display: flex;
    flex-direction: column;
    align-items: center;
    position: relative;
    box-shadow: 0 10px 25px rgba(0,0,0,0.125);
    border-radius: 20px;
    overflow: hidden;
}

.screen {
    font-size: 250%;
    height: 20%;
    width: 100%;
    background-color: #7fbf9f;
    outline: none;
    text-align: right;
    padding: 3.125%;
    border: none;
    display: flex;
    justify-content: flex-end;
    align-items: center;
}

.buttons {
    height: 80%;
    width: 100%;
    background-color: #dfdfdf;
    display: flex;
    flex-wrap: wrap;
}

.button:hover {
    background-color: #fff;
}

.button:active {
    transform: scale(0.875);
}

.button {
    margin: 2.5%;
    height: 17.5%;
    width: 20%;
    background-color: #efefef;
    border:none;
    border-radius: 8px;
    font-size: 150%;
}

.operator {
    background-color: #bbb;
}

.equal {
    background-color: #7fbf9f;
}

.clear {
    background-color: #bbb;
}