изменение при ресайзе

    .countdown-title {
  color: #396;
  font-weight: 100;
  font-size: 40px;
  margin: 40px 0px 20px;
}
 
.countdown {
  font-family: monospace;
    color: #fff;
    display: inline-block;
    font-weight: 100;
    text-align: center;
    font-size: 30px;
    position: absolute;
        top: 40%;
    margin-left: -1%;
}
 
.countdown-number {
 padding: 27px;
   border-radius: 44px;
    background: #ff823f;
    display: inline-block;
    margin: 0px 5px 0px 0;
}
 
.countdown-time {
      /* padding: 15px; */
    border-radius: 3px;
    /* background: #00816a; */
    display: inline-block;
    font-size: 76px;
}
 
.countdown-text {
  display: block;
  padding-top: 5px;
  font-size: 16px;
}

    <div id="countdown" class="countdown">
  <div class="countdown-number">
    <span id="numdays" class="days countdown-time"></span>
  </div>
  <div class="countdown-number">
    <span id="numhours" class="hours countdown-time"></span>
  </div>
  <div class="countdown-number">
    <span id="nummins" class="minutes countdown-time"></span>
  </div>
  <div class="countdown-number">
    <span id="numsecs" class="seconds countdown-time"></span>
  </div>
</div>

как сделать что бы при реcайзе изменялся countdown-number?