body {
  font-family: Arial, Helvetica, sans-serif;
  max-width: 600px;
  margin: 2rem auto;
  padding: 1rem;
  line-height: 1.5;
  text-align: center;
  background: #f0f8ff;
}

h1 {
  color: #0066cc;
}

.animation-container {
  position: relative;
  height: 200px;
  border: 2px dashed #0066cc;
  margin-top: 2rem;
}

.box {
  width: 50px;
  height: 50px;
  background: #ff6600;
  position: absolute;
  top: 75px;
  left: 0;
  animation: move 3s linear infinite alternate;
}

@keyframes move {
  from { left: 0; }
  to { left: calc(100% - 50px); }
}