style.css

html, body {
    margin: 0;
    padding: 0;
    font-family: 'Raleway', sans-serif;
    background: #F5F5F5;
    height: 100%;
    overflow: hidden;
}

* {
    box-sizing: border-box;
}

body {
    display: flex;
    flex-direction: column;
}

.wrap {
    display: flex;
    width: 100vw;
    flex-grow: 1;
    position: relative;
}

.dropzone {
    display: flex;
    flex-grow: 1;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

.placeholder {
    width: 100%;
    max-width: 500px;
    border-radius: 0.5em;
    background: #EEE;
    padding: 2em;
    text-align: center;
}

.placeholder p {
    font-size: 1.2rem;
    color: #999;
}

.viewer {
    width: 100%;
    height: 100%;
    flex-grow: 1;
    flex-shrink: 1;
    position: absolute;
    top: 0;
}


/******
 * 
 * Playback control
 * 
 * */


.hide {
    display:  none;
}

.audio-container{
    border-radius: 15px;
    padding: 20px 30px;
    margin: 0px auto;
    z-index: 10;
    position:absolute;
    width: 100%;
    top: 80%;
}

  .audio-container.play img {
    animation-play-state: running;
  }

  @keyframes rotate {
    from {
      transform: rotate(0deg);
    }
  
    to {
      transform: rotate(360deg);
    }
  }

  .navigation {
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1;
  }
  
  .action-btn {
    
    color: #000;
    font-size: 20px;
    cursor: pointer;
    padding: 10px;
    margin: 0 20px;
  }


  .action-btn.action-btn-big {
    color: #000;
    font-size: 30px;
  }

  .action-btn:focus {
    outline: 0;
  }

  .audio-info {
    /*background-color: rgb(255, 255, 255);*/
    padding: 10px;
    width: 80%;
    z-index: 0;
    margin: 20px auto;
  }
  
  .audio-container.play .audio-info {
    opacity: 1;
  }
  
  .audio-info h3 {
    text-align: center;
    margin: 0;
  }
  
  .progress-container {
    background: #ddd;
    border-radius: 5px;
    cursor: pointer;
    margin: 10px 0;
    height: 4px;
    width: 100%;
  }
  
  .progress {
    background-color: #000;
    border-radius: 5px;
    height: 100%;
    width: 50%;
    transition: width 0.1s linear;
  }










/******************************************************************************
 * Header
 */

header {
    display: flex;
    background: #353535;
    padding: 0 2em;
    height: 2rem;
    line-height: 2rem;
    align-items: center;
    overflow-x: auto;
    overflow-y: hidden;
    white-space: nowrap;
    box-shadow: 0px 0px 8px 2px rgba(0, 0, 0, 0.3);
    z-index: 1;

    -webkit-app-region: drag;
}

header h1,
header .item,
header .separator {
    color: #F5F5F5;
    font-weight: 300;
    line-height: 4rem;
    margin: 0;
}

header h1 {
    font-size: 1.4rem;
}

header h1 > a {
    color: inherit;
    font-size: inherit;
    text-decoration: inherit;
}

header .item {
    padding: 0 1em;
    font-size: 0.8rem;
    text-decoration: none;
    transition: background ease 0.2s;

    -webkit-app-region: no-drag;
}

header .item:hover {
    background: #444;
}

header button.item {
    height: 34px;
    line-height: 35px;
    padding: 0 1em;
    border: 0;
    background: #ffc107;
    color: #333;
    font-weight: 500;
    border-radius: 2px;
    cursor: pointer;
}

header button.item:hover {
    color: #000;
}

header .separator {
    margin: 0 0.2em;
    opacity: 0.2;
}

header h1 + .separator {
    margin-left: 1em;
}

.flex-grow {
    flex-grow: 1;
}

.gui-wrap {
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    overflow: auto;
    pointer-events: all;
}

.dg li.gui-stats:not(.folder) {
    height: auto;
}

@media screen and (max-width: 700px) {
    header h1 {
        font-size: 1em;
    }

    .layout-md {
        display: none;
    }
}

/******************************************************************************
 * Upload Button
 *
 * https://tympanus.net/Tutorials/CustomFileInputs/
 */

.upload-btn {
    margin-top: 2em;
}

.upload-btn input {
    width: 0.1px;
    height: 0.1px;
    opacity: 0;
    overflow: hidden;
    position: absolute;
    z-index: -1;
}

.upload-btn label {
    color: #353535;
    border: 0;
    border-radius: 3px;
    transition: background ease 0.2s;
    font-size: 1rem;
    font-weight: 700;
    text-overflow: ellipsis;
    white-space: nowrap;
    cursor: pointer;
    display: inline-block;
    overflow: hidden;
    padding: 0.625rem 1.25rem;
}

.upload-btn label:hover {
    background: #DDD;
}

.upload-btn svg {
    width: 1em;
    height: 1em;
    vertical-align: middle;
    fill: currentColor;
    margin-top: -0.25em;
    margin-right: 0.25em;
}

/******************************************************************************
 * CSS Spinner
 *
 * http://tobiasahlin.com/spinkit/
 */

.spinner {
    width: 40px;
    height: 40px;
    position: absolute;
    left: 50%;
    top: 50%;
    margin: -20px;

    background-color: #333;

    border-radius: 100%;
    -webkit-animation: sk-scaleout 1.0s infinite ease-in-out;
    animation: sk-scaleout 1.0s infinite ease-in-out;
}

@-webkit-keyframes sk-scaleout {
    0% {
        -webkit-transform: scale(0)
    }
    100% {
        -webkit-transform: scale(1.0);
        opacity: 0;
    }
}

@keyframes sk-scaleout {
    0% {
        -webkit-transform: scale(0);
        transform: scale(0);
    }
    100% {
        -webkit-transform: scale(1.0);
        transform: scale(1.0);
        opacity: 0;
    }
}