body {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 100vw;
  height: 100vh;
  margin: 0;
  background: #000000;
  overflow: hidden;
}

button {
  background: none;
  border: none;
  outline: none;
  cursor: pointer;
  margin: 0;
  padding: 0;
  vertical-align: top;
}

.hidden {
  position: absolute;
  left: -10000px;
  top: auto;
  width: 1px;
  height: 1px;
  overflow: hidden;
}

.contents {
  position: relative;
  width: 100vw;
  height: 100vh;
  max-width: 1000px;
  max-height: 1000px;
  overflow: hidden;
}

.button_wrap {
  position: absolute;
  top: 0;
  right: 0;
  padding: 15px 20px;
}

.btn_audio {
  width: 34px;
  height: 34px;
  text-indent: -9999px;
  font-size: 1px;
  opacity: 0.5;
  background-size: contain;
  background-repeat: no-repeat;
  overflow: hidden;
  -webkit-tap-highlight-color: rgba(255,255,255,0);
  -webkit-touch-callout:none;
  -webkit-user-select:none;
  -khtml-user-select:none;
  -moz-user-select:none;
  -ms-user-select:none;
  user-select:none;
}

.btn_audio.on {
  background-image: url('../images/audio.png');
}

.btn_audio.off {
  background-image: url('../images/mute.png');
}

.btn_audio.hide {
  display: none;
}

.img_audio {
  width: 100%;
}