style.css

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: 'Roboto Mono', sans-serif;
}

body {
  height: 100vh;
  background: #282A36;
}

.hidden {
  display: none;
  visibility: hidden;
}

header {
  display: flex;
  justify-content: space-between;
  padding: 35px;
  position: absolute;
  top: 0;
  width: 100%;
  font-size: 18px;
  color: #F774BF;
}

#score, #fails {
  color: #F4F0E6;
}

main {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  height: 100%;
}

main #challenge {
  font-size: 88px;
  margin: 35px;
  color: #7FE3FC;
  transform: scale(0);
  transition: transform .4s;
}

#options {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  padding: 35px;
}

button {
  color: #44E97A;
  background: #282A36;
  font-weight: 700;
  border: 2px solid #F774BF;
  padding: 10px 15px;
  margin: 10px;
  font-size: 18px;

  cursor: pointer;
}

#game-over {
  background: #282A36;
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  padding: 35px;

  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;

  text-align: center;
}

#game-over strong {
  font-size: 42px;
  color: #44E97A;  
}

#game-over strong span {
  color: #F4F0E6;
}

#score-gameover {
  color: #F1F688;
  margin: 20px 0;
}

footer {
  position: absolute;
  bottom: 0;
  width: 100%;

  display: flex;
  justify-content: center;
  align-items: center;
  padding: 15px 35px;
  background: rgba(0, 0, 0, .1);
  color: #F4F0E6;
}

footer img {
  width: 50px;
  border-radius: 50%;
  margin-right: 15px;
}

footer a {
  color: #44E97A;
}

@media screen and (max-width: 768px) {
  footer {
    font-size: 14px;
  }

  footer img {
    width: 25px;
  }
}

@media screen and (max-width: 437px) {
  footer span {
    max-width: 230px;
  }
}

@media screen and (max-width: 320px) {
  footer {
    font-size: 12px;
  }

  footer span {
    max-width: 190px;
  }
}