* {
    margin: 0;
    padding: 0;
    font-family: Verdana, Geneva, Tahoma, sans-serif;
}

body {
    background-color: rgb(58, 55, 55);
}

button:hover {
    cursor: pointer;
    opacity: 0.8;
}

button {
    width: 100px;
    height: 75px;
    font-size: 22px;
    margin: 1.5px -1px;
    border-radius: 7px;
    border: none;
    box-sizing: border-box;
    font-weight: 500;
}

.calculator {
    width: 420px;
    text-align: center;
    margin: 100px auto;
    background-color: black;
    box-sizing: border-box;
    border-radius: 10px;
    outline: 10px solid rgb(36, 148, 193);
    outline-style:solid;
}

.display {
    font-size: 75px;
    width: 420px;
    height: 90px;
    border: 1px solid black;
    padding-right: 3px;
    box-sizing: border-box;
}

.sec-display {
    font-size: 30px;
    width: 417px;
    height: 40px;
    background-color: rgb(40, 40, 40);
    color: whitesmoke;
    border-top-left-radius: 7px;
    border-top-right-radius: 7px;
    box-sizing: border-box;
    padding-right: 3px;
    font-weight: lighter;
}

.screen {
    border: 2px solid black;
    background-color: rgb(140, 160, 120);
    border-radius: 10px;
    text-align: right;
}

.main-body {
    margin: 5px 0px 0px;
    background-color: black;
    padding-bottom: 5px;
}

#equals {
    background-color: rgb(19, 177, 239);
}

.operand {
    background-color: gray;
}

#clear {
    background-color: rgb(19, 177, 239);
}

.operator {
    background-color: orange;
}

#zero {
    width: 202px;
    box-sizing: border-box;
}

#backspace {
    background-color:rgb(199, 22, 22);
}