* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: "Microsoft YaHei", Arial, sans-serif;
}
body {
  background: linear-gradient(135deg, #667eea, #764ba2);
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px;
  position: relative;
}

#loader {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(255, 255, 255, 0.95);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  z-index: 9999;
  transition: opacity 0.6s ease;
  backdrop-filter: blur(5px);
}
#loader.hidden {
  opacity: 0;
  pointer-events: none;
}
.spinner {
  width: 60px;
  height: 60px;
  border: 6px solid #f3f3f3;
  border-top: 6px solid #667eea;
  border-radius: 50%;
  animation: spin 1s linear infinite;
  margin-bottom: 20px;
}
@keyframes spin {
  0% {
    transform: rotate(0deg);
  }
  100% {
    transform: rotate(360deg);
  }
}
#loader p {
  font-size: 18px;
  color: #555;
}

.container {
  width: 100%;
  max-width: 480px;
  text-align: center;
}

.welcome {
  background: white;
  border-radius: 20px;
  padding: 60px 40px;
  box-shadow: 0 15px 35px rgba(0, 0, 0, 0.2);
  animation: fadeIn 1s;
}
@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.welcome h1 {
  font-size: 36px;
  margin-bottom: 20px;
  color: #333;
}
.welcome p {
  font-size: 18px;
  color: #666;
  margin-bottom: 40px;
}
.start-btn {
  padding: 16px 50px;
  font-size: 22px;
  background: #667eea;
  color: white;
  border: none;
  border-radius: 50px;
  cursor: pointer;
  box-shadow: 0 8px 20px rgba(102, 126, 234, 0.4);
  transition: all 0.3s;
}
.start-btn:hover {
  transform: translateY(-3px);
  box-shadow: 0 12px 25px rgba(102, 126, 234, 0.5);
}

.card {
  background: white;
  border-radius: 20px;
  padding: 30px 25px;
  box-shadow: 0 15px 35px rgba(0, 0, 0, 0.2);
  text-align: center;
  transition: all 0.4s;
  opacity: 0;
  transform: translateY(50px);
  display: none;
}
.card.show {
  opacity: 1;
  transform: translateY(0);
  display: block;
}

.progress {
  margin-bottom: 20px;
  font-size: 14px;
  color: #666;
}
.progress-bar {
  height: 8px;
  background: #eee;
  border-radius: 4px;
  overflow: hidden;
  margin-top: 8px;
}
.progress-fill {
  height: 100%;
  background: #667eea;
  width: 0;
  transition: width 0.6s;
}
.english {
  font-size: 42px;
  font-weight: bold;
  color: #333;
  margin: 20px 0;
}
.phonetic {
  font-size: 20px;
  color: #888;
  margin-bottom: 30px;
}
.options {
  display: grid;
  gap: 15px;
  margin-top: 30px;
}
.option {
  padding: 16px;
  font-size: 18px;
  border: 2px solid #ddd;
  border-radius: 12px;
  cursor: pointer;
  transition: all 0.3s;
  background: #fafafa;
}
.option:hover {
  border-color: #667eea;
  background: #f0f4ff;
}
.option.correct {
  background: #d4edda;
  border-color: #28a745;
}
.option.wrong {
  background: #f8d7da;
  border-color: #dc3545;
}
.hint {
  margin-top: 20px;
  font-size: 16px;
  color: #28a745;
  opacity: 0;
  transition: opacity 0.5s;
}
.hint.show {
  opacity: 1;
}
.next-btn {
  margin-top: 30px;
  padding: 12px 30px;
  background: #667eea;
  color: white;
  border: none;
  border-radius: 50px;
  font-size: 18px;
  cursor: pointer;
  display: none;
}
.next-btn.show {
  display: inline-block;
}
.complete {
  font-size: 24px;
  color: #28a745;
  padding: 40px;
}