style.css

@import url('https://fonts.googleapis.com/css?family=Open+Sans:300,700');

* {
  margin: 0;
  padding: 0;
  color: white;
  font-family: "Open Sans", serif;
  font-weight: 300;

  -webkit-transition: all 200ms ease-in-out;
  transition: all 200ms ease-in-out;
}

#game-canvas {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
}

#score-box, #game {
  border: 4px solid white;
  border-radius: 8px;
  background-color: rgba(0, 0, 0, 0.5);
}

#score-box {
  width: 320px;
  height: 180px;
}

#score-box h1 {
  font-size: 72px;
  font-weight: 700;
  text-align: center;
}

#tooltip {
  text-align: center;
}

#previous-color {
  font-weight: 700;
}

#game {
  margin-top: 20px;
  width: 320px;
  height: 180px;
}

#color-hex {
  text-align: center;
  margin: 10px 0;
}

#user-guess {
  color: black;
  text-align: center;
  font-size: 26px;
  width: 80%;
  margin: auto;
  margin-top: 10px;
  margin-bottom: 10px;
  display: block;
}

#confirm-btn {
  display: block;
  font-size: 32px;
  font-weight: 700;
  border-style: none;
  border-radius: 16px;
  padding: 5px;
  width: 50%;
  margin: auto;
  text-align: center;
  box-shadow: 0px 5px 5px 3px rgba(0, 0, 0, 0.5);
}

#confirm-btn:hover {
  cursor: pointer;
  box-shadow: 0px 10px 10px 3px rgba(0, 0, 0, 0.5);
}