style.css

* {
  margin: 0;
  padding: 0;
  font-family: cursive;
}

body {
  background: #0bf749;
  color: #333;
}

.container {
  position: absolute;
  top: 80px;
  left: 100px;
  right: 100px;
  bottom: 80px;
  background: rgb(204, 248, 165);
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;
  border-radius: 9px;
  box-shadow: 0px 50px 50px rgba(0, 0, 0, 0.5),
    0px 0px 0px 100px rgba(0, 0, 0, 0.1);
}

.container .txt {
  text-align: center;
  font-size: 2em;
  line-height: 0.7em;

  margin-top: 30px;
}

.container .by {
  margin-top: 80px;
  font-size: 18px;
  font-weight: 100;
}

.date_input {
  position: relative;
  top: 40px;
  text-align: center;
}

.date_input h2 {
  margin-bottom: 10px;
  font-size: 18px;
}

.date_input input {
  border-radius: 5px;
  background-color: rgba(255, 255, 255, 0.3);
  padding: 3px;
  margin: 3px;
  outline: none;
}

.countdown {
  display: flex;
  margin-top: 80px;
}

.countdown div {
  position: relative;
  width: 100px;
  height: 100px;
  line-height: 100px;
  text-align: center;
  background: #333;
  color: #fff;
  margin: 0 15px;
  font-size: 3em;
  font-weight: 500;
  border-radius: 6px;
}

.countdown div::before {
  content: "";
  position: absolute;
  bottom: -30px;
  left: 0;
  width: 100%;
  height: 35px;
  background: #ff0;
  color: #333;
  font-size: 0.35em;
  line-height: 35px;
  font-weight: 300;
}

.countdown #day::before {
  content: "Days";
}
.countdown #hour::before {
  content: "Hours";
}
.countdown #minute::before {
  content: "Minutes";
}
.countdown #second::before {
  content: "Seconds";
}