html {
    max-width: 70ch;
    padding: 3em 1em;
    margin: auto;
    line-height: 1.75;
    font-size: 1.25em;
    text-align: center;
}

#preview {
    overflow: hidden;
    margin-bottom: 10px;
}

#preview img {
    display: block;
    max-width: 100%;
    max-height: 100%;
    margin: auto;
}

/* https://codepen.io/sebj54/pen/ogvzdr */
.btn {
    position: relative;

    display: block;
    margin: 30px auto;
    padding: 0;

    overflow: hidden;

    border-width: 0;
    outline: none;
    border-radius: 2px;
    box-shadow: 0 1px 4px rgba(0, 0, 0, .6);

    background-color: #03a9f4;
    color: #ecf0f1;

    transition: background-color .3s;
}

.btn:hover,
.btn:focus {
    background-color: #23b9fc;
}

.btn:disabled {
    background-color: #cacaca;
}

.btn>* {
    position: relative;
}

.btn span {
    display: block;
    padding: 12px 24px;
}

.btn:before {
    content: "";

    position: absolute;
    top: 50%;
    left: 50%;

    display: block;
    width: 0;
    padding-top: 0;

    border-radius: 100%;

    background-color: rgba(236, 240, 241, .3);

    -webkit-transform: translate(-50%, -50%);
    -moz-transform: translate(-50%, -50%);
    -ms-transform: translate(-50%, -50%);
    -o-transform: translate(-50%, -50%);
    transform: translate(-50%, -50%);
}

.btn:active:before {
    width: 120%;
    padding-top: 120%;

    transition: width .2s ease-out, padding-top .2s ease-out;
}


/*http://jsfiddle.net/4cwpLvae/*/
input[type="file"] {
    display: none;
}

.custom-file-upload {
    border: 1px solid #ccc;
    display: inline-block;
    padding: 6px 12px;
    cursor: pointer;
    margin: 20px auto;
    display: block;
    width: 50%;
    text-align: center;
}

/*https://codingbeautydev.com/blog/material-design-text-field/*/
.input-container {
    position: relative;
}

.input-container input {
    height: 48px;
    width: 50%px;
    border: 1px solid #c0c0c0;
    border-radius: 4px;
    box-sizing: border-box;
    padding: 16px;
}

.input-container .label {
    position: absolute;
    top: 0;
    bottom: 0;
    left: 16px;
    display: flex;
    align-items: center;
    pointer-events: none;
}

.input-container input,
.label .text {
    font-family: 'Segoe UI';
    font-size: 16px;
}

.input-container .label .text {
    transition: all 0.15s ease-out;
    color: grey;
}

.input-container input:focus {
    outline: none;
    border: 2px solid blue;
}

.input-container input:focus+.label .text,
:not(input[value=""])+.label .text {
    font-size: 12px;
    transform: translate(0, -150%);
    background-color: white;
    padding-left: 4px;
    padding-right: 4px;
}

.input-container input:focus+.label .text {
    color: blue;
}

#progressBar {
    width: 50%;
    height: 38px;
    background-color: #f2f2f2;
    border-radius: 4px;
    overflow: hidden;
    margin: 20px auto;
  }

  #progressBar .progress {
    width: 0%;
    height: 100%;
    background-color: #4CAF50;
  }