style.css

*,
::after,
::before {
  box-sizing: border-box;
}

html {
  background-color: rgb(238, 238, 207);
  font-family: monospace;
  color: white;
}

body {
  margin: 0 auto;
  width: 90 vw;
  height: 90vh;
}

header {
  position: relative;
  background-color: rgb(63, 97, 209);
  padding: 4rem 2rem 2rem;
  margin: 0 auto;
}

h1,
p {
  padding-left: 5%;
}

button {
  font: inherit;
  position: absolute;
  right: 10%;
  top: 35%;
  border: 0;
  height: 5rem;
  width: 10rem;
  box-shadow: 0.5rem 0.5rem black;
}

main {
  position: relative;
  height: 60vh;
}

.counter-block {
  display: flex;
  width: 100%;
  height: 120%;
}

.counter {
  color: black;
  font-size: 10rem;
  position: absolute;
  top: 30%;
  left: 50%;
  transform: translate(-50%, -50%);
}

.left-block {
  background-color: rgb(47, 47, 225);
  width: 0;
  height: 100%;
}

.right-block {
  background-color: rgb(26, 26, 202);
  width: 100%;
  height: 100%;
}