style.css

* {
  margin: 0;
  padding: 0;
  box-sizing: inherit;
}

html {
  font-size: 62.5%;
  box-sizing: border-box;
}

body {
  font-family: 'Press Start 2P', sans-serif;
  color: #eee;
  background-color: #222;

}

/* LAYOUT */
header {
  position: relative;
  height: 35vh;
  border-bottom: 7px solid #eee;
}

main {
  height: 65vh;
  color: #eee;
  display: flex;
  align-items: center;
  justify-content: space-around;
}

.left {
  width: 52rem;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.right {
  width: 52rem;
  font-size: 2rem;
}

/* ELEMENTS STYLE */
h1 {
  font-size: 4rem;
  text-align: center;
  position: absolute;
  width: 100%;
  top: 52%;
  left: 50%;
  transform: translate(-50%, -50%);
}

.number {
  background: #eee;
  color: #333;
  font-size: 6rem;
  width: 15rem;
  padding: 3rem 0rem;
  text-align: center;
  position: absolute;
  bottom: 0;
  left: 50%;
  transform: translate(-50%, 50%);
}

.between {
  font-size: 1.4rem;
  position: absolute;
  top: 2rem;
  right: 2rem;
}

.again {
  position: absolute;
  top: 2rem;
  left: 2rem;
}

.guess {
  background: none;
  border: 4px solid #eee;
  font-family: inherit;
  color: inherit;
  font-size: 5rem;
  padding: 2.5rem;
  width: 25rem;
  text-align: center;
  display: block;
  margin-bottom: 3rem;
}

.btn {
  border: none;
  background-color: #eee;
  color: #222;
  font-size: 2rem;
  font-family: inherit;
  padding: 2rem 3rem;
  cursor: pointer;
}

.btn:hover {
  background-color: #ccc;
}

.message {
  margin-bottom: 8rem;
  height: 3rem;
}

.label-score {
  margin-bottom: 2rem;
}


/* 1rem= 1em = 16px */


/* *******************************
          BELOW 704px           
**********************************/

@media(max-width: 44em){
  html{
    font-size: 50%;
  }
}

/* *******************************
          BELOW 560px           
**********************************/
@media(max-width: 35em){
  html{
    font-size: 45%;
  }
}

/* *******************************
          BELOW 440px           
**********************************/
@media(max-width: 28em){
  main{
    display: inline;
  }

  .guess{
    margin-top: 10.8rem;
    margin-bottom: 4.8rem;
    font-size: 4rem;
    padding: 2.1rem;
    border: 3px solid #eee;
  }

  h1{
    display: flex;
    line-height: 1.4;
  }

  .check{
    margin-bottom: 4rem;
  }

  .right{
    margin-left: 3.2rem;
  }

  .again{
    font-size: 1.4rem;
    padding: 1.4rem 2.4rem;
  }
}