#puzzle-container {
  width: 500px;
  height: 300px;
  display: grid;
  margin: 40px auto;
}

.puzzle-piece {
  background-size: 500px 300px;
  background-repeat: no-repeat;
  background-color: #f1f1f1;
  border: 1px solid #e4e4e4;
  opacity: 0;
  width: 100%;
  height: 100%;
}

.visible {
  opacity: 1;
}

.instructions {
  max-width: 720px;
  margin: 24px auto;
  text-align: left;
  line-height: 1.5;
  font-size: 18px;
}