calculator.css

html {
    box-sizing: border-box;
}

*, *:before, *:after {
    box-sizing: inherit;
}

body {
    padding: 0;
    margin: 0;
}

.wrapper {
    width: 400px;
    background-color: black;
    color: white;
    border: 1rem solid #333333;
    border-radius: 10px;
    filter: blur(0.6px);
    margin: 15vh auto;
    box-shadow: 20px 12px 30px 10px #666666;
}

.screen {
    text-align: right;  
    font-family: Courier, 'Courier New', monospace;
    font-size: 40px;
    padding: 20px 5px;
}

.calc-button-row {
    display: flex;
    flex-flow: row nowrap;
    justify-content: space-between;
    margin-top: 0.5%;
}

.calc-button {
    color: black;
    background-color: #D8D9DB;    
    font-size: 40px;
    height: 100px;
    flex-basis: 24.5%;
    transition: background-color 0.05s ease;
    cursor: pointer;
}

.calc-button:hover {
    background-color: #EBEBEB;
}

.calc-button:active {
    background-color: #BBBCBE;
}

.double {
    flex-basis: 49.7%;
}

.triple {
    flex-basis: 74.8%;
}

.calc-button:last-child {
    border-color: #EFA85F;
    background-color: #DF974C;
    color: white;
}

.calc-button:last-child:hover {
    background-color: #DFB07E;
}

.calc-button:last-child:active {
    background-color: #DD8D37;
}