.display_area {
  width: 900px;
}

.info_txt {
  font-size: 1.2em;
}

#btn_disable {
  pointer-events: none;
  /* 無効っぽい見た目にする */
  color: #999;
}

.stepper {
  background-image: radial-gradient(#fff 55%, transparent 55%), conic-gradient(#32CD32 17%, #e2e2e2 17% 100%);
}

@media screen and (max-width: 480px) {
  .display_area {
    width: 320px;
  }

}