.button-month {
  --width-button-month: 180;
  bottom: 8%;
  width: calc(var(--width-button-month) * 1px);
  z-index: 3;
}

#button-month-1 {
  right: calc(50% + 10px);
}

#button-month-2 {
  left: calc(50% + 10px);
}

@media screen and (max-width: 1000px) {
  .button-month {
    width: calc(var(--width-button-month) / 1000 * 100vw);
  }

  #button-month-1 {
    right: calc(50% + 10 / 1000 * 100vw);
  }

  #button-month-2 {
    left: calc(50% + 10 / 1000 * 100vw);
  }
}