body {
  margin: 0;
  font-family: sans-serif;
  background: #f4f7f3;
  color: #333;
}

.app {
  max-width: 430px;
  margin: 0 auto;
  padding: 20px;
}

header,
.card {
  background: #fff;
  border-radius: 18px;
  padding: 22px;
  margin-bottom: 18px;
  box-shadow: 0 4px 12px rgba(0,0,0,0.08);
}

.level,
.tag {
  display: inline-block;
  background: #6b8f71;
  color: #fff;
  padding: 6px 12px;
  border-radius: 999px;
  font-size: 14px;
  margin-bottom: 10px;
}

h1 {
  font-size: 30px;
  color: #35543b;
  margin: 10px 0;
}

#grammar-meaning {
  font-size: 22px;
  font-weight: bold;
}

.example {
  font-size: 19px;
  line-height: 1.7;
  margin: 12px 0;
}

#question {
  font-size: 20px;
  font-weight: bold;
  line-height: 1.6;
}

.choice {
  width: 100%;
  padding: 14px;
  margin: 8px 0;
  border: none;
  border-radius: 12px;
  font-size: 18px;
  background: #e8eee6;
  cursor: pointer;
}

.choice:hover {
  background: #d6e2d3;
}

.answer {
  display: none;
  margin-top: 15px;
  padding: 12px;
  border-radius: 12px;
  background: #eef7ec;
  color: #2f6b3a;
  font-weight: bold;
  font-size: 18px;
}

#practice {
  font-size: 20px;
  background: #f8f8f8;
  padding: 14px;
  border-radius: 12px;
}

.nav {
  display: flex;
  gap: 10px;
}

.nav button {
  flex: 1;
  padding: 14px;
  border: none;
  border-radius: 12px;
  background: #6b8f71;
  color: white;
  font-size: 18px;
}
.audio-btn {
  width: 120px;
  height: 44px;
  border: none;
  border-radius: 22px;
  background: #e8f0e8;
  font-size: 20px;
  margin: 16px 0;
}
.audio-btn {
  width: 120px;
  height: 44px;
  border: none;
  border-radius: 22px;
  background: #e8f0e8;
  font-size: 20px;
  display: block;
  margin: 16px auto;
}