* {
    margin: 0;
    padding: 0;
    -webkit-tap-highlight-color: rgba(0, 0, 0, 0);
    -moz-user-focus: none;
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
}

html,
body {
    height: 100%;
}

body {
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: #eee;
    overflow: hidden;
}

#calculator {
    --button-width: 12vmin;
    --button-height: 12vmin;

    display: grid;
    grid-template-areas:
        'result result result result'
        'clear sign percent divide'
        'number-7 number-8 number-9 multiply'
        'number-4 number-5 number-6 subtract'
        'number-1 number-2 number-3 add'
        'number-0 number-0 dot equal';
    grid-template-columns: repeat(4, var(--button-width));
    grid-template-rows: calc(var(--button-height) + 4vmin) repeat(5, var(--button-height));
    box-shadow: -1vmin -1vmin 2vmin -1vmin #fff, 1vmin 1vmin 2vmin -1vmin rgba(0, 0, 0, 0.1);
    border-radius: 3vmin;
    padding: 3vmin;
    overflow: hidden;
}

#calculator button {
    cursor: pointer;
    margin: 1vmin;
    border: none;
    outline: none;
    border-radius: calc(var(--button-height) / 2);
    font-size: 4vmin;
    font-family: Arial, Helvetica, sans-serif;
    color: #999;
    background-image: linear-gradient(135deg, rgb(230, 230, 230) 0%, rgba(246, 246, 246, 1) 100%);
    box-shadow: -0.5vmin -0.5vmin 2vmin -0.5vmin #fff, 0.5vmin 0.5vmin 2vmin -0.5vmin rgba(0, 0, 0, 0.1);
}

#calculator button:active {
    font-size: 3.6vmin;
    box-shadow: -0.5vmin -0.5vmin 2vmin -0.5vmin #fff inset, 0.5vmin 0.5vmin 2vmin -0.5vmin rgba(0, 0, 0, 0.1) inset;
}

#calculator .result {
    margin: 1vmin 1vmin 3vmin;
    box-shadow: -1vmin -1vmin 2vmin -1vmin #fff inset, 1vmin 1vmin 2vmin -1vmin rgba(0, 0, 0, 0.1) inset;
    border-radius: 1vmin;
    overflow: hidden;
}

#calculator .screen {
    display: flex;
    flex-direction: row-reverse;
    width: calc(100% - 1.8vmin);
    height: 100%;
    padding-bottom: 30px;
    margin: 0 auto;
    overflow-x: scroll;
    color: #666;
    font-size: 6.9vmin;
    font-family: Arial, Helvetica, sans-serif;
    line-height: var(--button-height);
    white-space: nowrap;
}