style.css

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

body {
  display: flex;
  justify-content: center;
  align-items: center;
  background-image: linear-gradient(to top, #09203f 0%, #537895 100%);
  height: 100vh;
}

.container {
  position: relative;
  width: 80vw;
  aspect-ratio: 2.179;
  background: #161b22;
  border: 5px solid black;
  border-style: ridge;
  box-shadow: #00000066 0px 30px 90px;
  overflow: hidden;
}

.ball {
  width: 9.09%;
  aspect-ratio: 1;
  background: radial-gradient(circle at 30% 30%, #ff0000, #000000);
  border-radius: 50%;
  position: absolute;
  bottom: 0;
  left: 0;
  animation: bounce 4s linear alternate infinite;
}

@keyframes bounce {
  10% {
    transform: translate(100%, -400%);
  }

  20% {
    transform: translate(200%, 0);
  }

  30% {
    transform: translate(300%, -400%);
  }

  40% {
    transform: translate(400%, 0);
  }

  50% {
    transform: translate(500%, -400%);
  }

  60% {
    transform: translate(600%, 0);
  }

  70% {
    transform: translate(700%, -400%);
  }

  80% {
    transform: translate(800%, 0);
  }

  90% {
    transform: translate(900%, -400%);
  }

  100% {
    transform: translate(1000%, 0);
  }
}