style.css

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

#game-board {
  background-image: url(/imagens/background\ mario.jpg);
  background-size: cover;
  margin: auto;
  width: 80%;
  height: 500px;
  position: relative;
  border: solid 3px black;
  overflow: hidden;
}

.clouds {
  position: absolute;
  top: 50px;
  width: 300px;
  animation: clouds-animation 20s infinite linear;
}

.mario {
  width: 150px;
  position: absolute;
  bottom: 0;
}

.pipe {
  width: 80px;
  position: absolute;
  bottom: 0;
  animation: pipe-animation 1.5s infinite linear;
}

.jump {
  animation: mario-jump 600ms ease-out;
}

@keyframes clouds-animation {
  from {
    right: -300px;
  }

  to {
    right: 100%;
  }
}

@keyframes pipe-animation {
  from {
    right: -80px;
  }

  to {
    right: 100%;
  }
}

@keyframes mario-jump {
  0% {
    bottom: 0;
  }

  40% {
    bottom: 180px;
  }

  50% {
    bottom: 180px;
  }

  60% {
    bottom: 180px;
  }

  100% {
    bottom: 0;
  }
}