body {
    margin: 0;
    font-family: 'Segoe UI', sans-serif;
    background: linear-gradient(to right, #ffddee, #ffe6f0);
    color: #333;
    text-align: center;
    height: 100vh;
    overflow: auto;
  }

  .start-screen {
    position: fixed;
    inset: 0;
    background: linear-gradient(to right, #ffccd5, #ffe6f0);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    z-index: 9999;
  }

  .start-screen button {
    padding: 16px 32px;
    font-size: 20px;
    background-color: #ff77aa;
    color: white;
    border: none;
    border-radius: 12px;
    cursor: pointer;
    box-shadow: 0 5px 15px rgba(0,0,0,0.1);
    transition: 0.3s;
  }

  .start-screen button:hover {
    background-color: #ff5e9c;
  }

  .quiz-container {
    background: white;
    border-radius: 20px;
    padding: 32px;
    max-width: 600px;
    margin: 0 auto;
    box-shadow: 0 10px 30px rgba(0,0,0,0.1);
    margin-top: 10vh;
    display: none;
  }

  .quiz-container h2 {
    font-size: 26px;
    margin-bottom: 24px;
  }

  .options button {
    display: block;
    width: 100%;
    margin: 10px 0;
    padding: 18px;
    border: none;
    border-radius: 10px;
    background-color: #ff99bb;
    color: white;
    font-size: 20px;
    cursor: pointer;
    transition: 0.3s;
  }

  .options button:hover {
    background-color: #ff77aa;
  }

  #result {
    font-size: 20px;
    color: #cc3366;
    margin-top: 32px;
  }

  .music-btn {
    position: fixed;
    top: 15px;
    right: 15px;
    background-color: #ff77aa;
    color: white;
    border: none;
    padding: 10px 16px;
    border-radius: 10px;
    cursor: pointer;
    font-size: 14px;
    box-shadow: 0 2px 6px rgba(0,0,0,0.1);
  }

  #popup {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.5);
  z-index: 9999;
  justify-content: center;
  align-items: center;
}

#popup > div {
  background: white;
  border-radius: 20px;
  padding: 32px;
  max-width: 90%;
  text-align: center;
  position: relative;
}

#popup-img {
  width: 200px;
  max-width: 100%;
}

#popup-msg {
  margin-top: 16px;
  font-size: 20px;
  color: #cc3366;
}

#popup button {
  margin-top: 16px;
  padding: 10px 20px;
  background-color: #ff77aa;
  color: white;
  border: none;
  border-radius: 10px;
  cursor: pointer;
  font-size: 20px;
}

@keyframes bounceIn {
  0% {
    transform: scale(0.6);
    opacity: 0;
  }
  60% {
    transform: scale(1.1);
    opacity: 1;
  }
  80% {
    transform: scale(0.95);
  }
  100% {
    transform: scale(1);
  }
}

#popup.show {
  display: flex;
}

#popup.show > div {
  animation: bounceIn 0.6s ease;
}


/*chuyển cảnh câu hỏi mượt*/
.fade-out {
  opacity: 0;
  transition: opacity 0.5s ease;
}

.fade-in {
  opacity: 1;
  transition: opacity 0.5s ease;
}

  /* Responsive for mobile */
  @media (max-width: 600px) {
    .quiz-container {
      padding: 20px;
      margin-top: 5vh;
    }

    .quiz-container h2 {
      font-size: 22px;
    }

    .options button {
      font-size: 18px;
      padding: 16px;
    }

    .start-screen button {
      font-size: 18px;
      padding: 14px 28px;
    }

    #result {
      font-size: 18px;
    }

    .music-btn {
      font-size: 12px;
      padding: 8px 12px;
    }
  }