*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    list-style: none;
    text-decoration: none;
}

body{
    font-family:  sans-serif ;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color:#eee;
}

.main-div{
    height: 600px;
    width: 330px;
    margin: 30px auto;
    padding: 10px;
    position: relative;
    background: linear-gradient(to right,#222,#333);
    border: 5px solid black;
    border-radius: 30px;
    animation: scaleIn 0.5s ease;
}

@keyframes scaleIn {
    from{
        transform: scale(0.5);
        opacity: 0.5;
    }

    to{
        transform: scale(1);
        opacity: 1;
    }
}

.screen{
    height: 100px;
    width: 100%;
    background: #2c3e50;
    font-size: 32px;
    text-align: right;
    border-radius: 20px;
    line-height: 100px;
    padding: 0 10px;
    color: #fff;
    font-weight: bold;
}

.number-div{
    padding: 6px 20px;
    margin: auto;
    width: 100%;
    display: flex;
    flex-direction: row;
    flex-wrap: wrap;
    justify-content: center;   
}

.number-div li{
    flex: 22%;
    height: 65px;
    width: 20px;
    background:#444 ;
    margin: 15px 2px;
    text-align: center;
    line-height: 65px;
    border-radius: 50%;
    font-weight: bold;
    font-size: 32px;
    cursor: pointer;
    color: #fff;
    transition: border 0.4s ease-in-out;
}

.number-div li.AC,
.number-div li.Change-Sign,
.number-div li.Percentage{
  background-color: grey ;
}


.number-div li.equal,
.number-div li.plus,
.number-div li.Minus,
.number-div li.Multiplication,
.number-div li.Division{
background-color : #d87c00 ;
}

.number-div li:active {
    background-color: #555;
    transform: scale(0.95);
    
}

.AC span {
  display: inline-block;
  transition: opacity 0.2s ease;
}

.AC span.fade-out {
  opacity: 0;
}

.AC span.fade-in {
  opacity: 1;
}