html, body{
    box-sizing: border-box;
    padding: 0;
    background: linear-gradient(to right, #09203F ,#537895);
}
.display {
    width: 325px;
    height: 585px;
    border: 5px solid lightsalmon;
    margin: 100px auto;
    border-radius: 10px;
    background-color: #e6e6e6
}

#display {
    box-sizing: border-box;
    width: 97%;
    height: 80px;
    border-width: 2px 2px 2px 2px;
    border-color: lightgrey;
    font-size: 40px;
    line-height: 80px;
    text-align: right;
    font-weight: bold;
    padding: 0px 10px 0px 10px;
    margin:5px;
}

.button {
    border-width: 0.1px;
    border-radius: 25px;
    margin: 2px;
    width: 75px;
    height: 75px;
    background-color: #e6e6e6;
    float: left;
    font-size: 17px;
    transition-duration: 0.3s;
    box-shadow: 0 3px #999;
    outline: none;
}
.keys{
  margin:4px;
}

.button:hover {
    background-color: #8c8c8c;
    color: #e6e6e6;
    box-shadow: 0 12px 16px 0 rgba(0,0,0,0.24), 0 17px 50px 0 rgba(0,0,0,0.19);
}

.button:active {
  box-shadow: 0 1px #666;
  transform: translateY(1.5px);
}

.keys__first .button{
    background-color: slategrey;
    transition-duration: 0.3s;
    margin-top: 15px;
}

.keys__first .button:hover {
    background-color: #8c8c8c;
    color: #e6e6e6;
    box-shadow: 0 6px 6px 0 rgba(0,0,0,0.24), 0 17px 50px 0 rgba(0,0,0,0.19);
}