/* 海っぽい深海グラデーション背景 */
body {
  margin: 0;
  font-family: 'Segoe UI', sans-serif;
  background: radial-gradient(circle at bottom, #002b40 0%, #000e1a 100%);
  overflow: hidden;
  color: #ffffff;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  position: relative;
}

/* 泡のスタイル */
.bubble {
  position: absolute;
  bottom: -60px;
  background-color: rgba(255, 255, 255, 0.2);
  border-radius: 50%;
  animation: rise 12s infinite ease-in;
  opacity: 0.7;
  pointer-events: none;
  z-index: 0;
}

@keyframes rise {
  0% {
    transform: translateY(0) scale(1);
    opacity: 0.7;
  }
  100% {
    transform: translateY(-120vh) scale(0.5);
    opacity: 0;
  }
}

.quiz-container {
  position: relative;
  z-index: 2;
  background: rgba(255, 255, 255, 0.9);
  color: #004d40;
  padding: 30px;
  border-radius: 15px;
  box-shadow: 0 8px 16px rgba(0,0,0,0.2);
  width: 90%;
  max-width: 600px;
  text-align: center;
}

.btn-group {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-top: 20px;
}

button {
  padding: 12px 20px;
  font-size: 1rem;
  background-color: #00bcd4;
  color: white;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: background 0.3s;
}

button:hover {
  background-color: #0097a7;
}

#result {
  margin-top: 20px;
  font-size: 1.1rem;
  font-weight: bold;
}

#stats {
  font-weight: bold;
  margin-bottom: 10px;
}