app.css

body{
  padding: 0;
  font-family: 'Roboto', sans-serif;
  background-color: #FFFFFF;
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  margin: auto;
}

h1{
  text-transform: capitalize;
  color: #A155B9;
}

#container{
  text-align:center;
  background-color: white;
  padding: 1%;
  width: 50%;
  border-radius: 10px;
}

header{
  margin-top: 3%;
}

input[type=text] {
  width: 30%;
  height: auto;
  font-size: 1.1rem;
  font-family : inherit;
  margin: 2%;
}

#buttoncolour {
  cursor: pointer;
  width: 30%;
  height: auto;
  font-size: 1rem;
  font-family: inherit;
  margin-bottom: 2%;

}

#resultr{
  color: red;
}

#resultg{
  color: green;
}

#resultb{
  color: blue;
}

hr{
  width: 70%;
  margin-bottom: 5%;
}

@media only screen
and (min-device-width : 320px)
and (max-device-width : 480px) {
  
#container{
    padding: 0;
    width: 70%;
    border-radius: 0;
  }

  input[type=text] {
    width: 60%;
    font-size: 0.8rem;
  }

  #buttoncolour {
    width: 60%;
  }
}