body {
  margin: 0;
  background: transparent;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

#playBtn {
  width: 56px;
  height: 56px;
  border-radius: 50%;
  border: none;
  cursor: pointer;

  background: rgb(17, 34, 33); /* navy */
  color: #fff;
  font-size: 20px;

  box-shadow: 0 6px 18px rgba(0,0,0,0.25);
  transition: transform 0.2s ease, opacity 0.2s ease;
}

#playBtn:hover {
  transform: scale(1.08);
  opacity: 0.9;
}