header {
  display: inline-block;
  width: 100%;
  margin-bottom: 30px;
}

#mainVisual article .mv_bg {
  width: 100%;
}
#mainVisual article .mv_msg {
  font-family: "Darumadrop One", cursive;
  font-size: 2em;
  color: #fff;
  text-align: center;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}
#mainVisual article .mv_msg span.ball {
  width: 25px;
  height: 25px;
  margin-right: 10px;
  margin-left: 10px;
  margin-bottom: -3px;
}