body {
  margin: 0;
  font-family: Arial;
  background: radial-gradient(circle, #0b0f2a, #000);
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  color: white;
}

/* 🌌 Stars */
.stars {
  position: fixed;
  width: 100%;
  height: 100%;
  z-index: -1;
}

.star {
  position: absolute;
  width: 2px;
  height: 2px;
  background: white;
  border-radius: 50%;
  animation: blink 2s infinite;
}

@keyframes blink {
  0%,100% { opacity: 0.2; }
  50% { opacity: 1; }
}

/* Container */
.quiz-container {
  width: 350px;
  text-align: center;
}

/* 🌈 Gradient Animated Progress Bar */
.progress-bar {
  width: 100%;
  height: 10px;
  background: rgba(255,255,255,0.1);
  border-radius: 20px;
  overflow: hidden;
  margin-bottom: 15px;
}

#progress-fill {
  height: 100%;
  width: 0%;
  border-radius: 20px;
  background: linear-gradient(90deg, #00f2fe, #4facfe, #00f2fe);
  background-size: 200% 100%;
  animation: shimmer 2s linear infinite;
  transition: width 0.4s ease;
}

@keyframes shimmer {
  0% { background-position: 0% 0; }
  100% { background-position: 200% 0; }
}

/* Card */
.card {
  perspective: 1000px;
}

.inner-card {
  position: relative;
  width: 100%;
  height: 280px;
  transition: transform 0.8s;
  transform-style: preserve-3d;
}

.card.flip .inner-card {
  transform: rotateY(180deg);
}

.front, .back {
  position: absolute;
  width: 100%;
  height: 100%;
  background: rgba(255,255,255,0.08);
  backdrop-filter: blur(10px);
  border-radius: 12px;
  padding: 20px;
  backface-visibility: hidden;
}

.back {
  transform: rotateY(180deg);
}

/* Answers */
.answer {
  display: block;
  width: 100%;
  margin: 5px 0;
  padding: 10px;
  background: #111;
  color: white;
  border: none;
  border-radius: 5px;
  cursor: pointer;
}

.answer:hover {
  box-shadow: 0 0 10px cyan;
}

/* Button */
#next {
  padding: 10px;
  background: green;
  color: white;
  border: none;
  border-radius: 5px;
}