popup.css

body {
    width: 200px;
    height: 324px;
    background-color: #f5f5f5;
}

h2 {
    clear: both;
    margin: auto;
}

#heart {
    padding: 0 0.2em;
    position: relative;
    color: red;
    margin-right: 5px;
}

    #heart::after {
        content: '';
        position: absolute;
        display: block;
        top: 47%;
        left: 1px;
        transform: translateY(-50%);
        width: 1.2em;
        height: 1.2em;
        border: 1px solid #454545;
        border-radius: 50%;
        margin: 0;
        position: absolute;
        top: 50%;
        left: 50%;
        margin-right: -50%;
        transform: translate(-50%, -50%);
    }

.display_area {
    float: left;
    position: relative;
    width: 75px;
    height: 35px;
    margin: auto;
    margin-top: 5px;
    margin-bottom: 20px;
}

#display_status {
    margin: 0;
    position: absolute;
    top: 50%;
    left: 50%;
    margin-right: -50%;
    transform: translate(-50%, -50%);
    font-size: 15px;
}

.display_input {
    position: absolute;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    z-index: 5;
    opacity: 0;
    cursor: pointer;
}

.display_label {
    width: 75px;
    height: 35px;
    background: #ccc;
    position: relative;
    display: inline-block;
    border-radius: 40px;
    transition: 0.4s;
    box-sizing: border-box;
}

    .display_label:after {
        content: "";
        position: absolute;
        width: 35px;
        height: 35px;
        border-radius: 100%;
        left: 0;
        top: 0;
        z-index: 2;
        background: #fff;
        box-shadow: 0 0 5px rgba(0, 0, 0, 0.2);
        transition: 0.4s;
    }

.display_input:checked + .display_label {
    background-color: #4BD865;
}

    .display_input:checked + .display_label:after {
        left: 40px;
    }

.display_area {
    float: left;
}

form {
    margin-top: 5px;
    margin-bottom: 20px;
}

input[type="number"] {
    width: 40px;
}

#transparency, #transparency_display {
    margin-top: 10px;
    float: left;
}

pre {
    font-size: 15px;
}

button {
    position: absolute;
    bottom: 10px;
    display: block;
    width: 200px;
}