body {
  background: #111;
  color: #0f0;
  font-family: monospace;
  font-size: 24px;
  padding: 20px;
}

.cursor {
  display: inline-block;
  width: 10px;
  background-color: #0f0;
  animation: blink 1s infinite;
  height: 1em;
  margin-left: 3px;
}

@keyframes blink {
  0%, 50% { opacity: 1; }
  50.01%, 100% { opacity: 0; }
}