* { box-sizing: border-box; margin: 0; padding: 0; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang HK", sans-serif;
  background: #e3f2fd;
  color: #222;
  padding: 10px;
  max-width: 420px;
  margin: 0 auto;
  text-align: center;
}
header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 15px; }
h1 { font-size: 1.6rem; }
.big-btn {
  background: #2196f3;
  color: white;
  border: none;
  border-radius: 12px;
  padding: 16px 28px;
  font-size: 1.3rem;
  min-height: 56px;
  cursor: pointer;
  margin: 8px;
}
#choices { display: flex; flex-wrap: wrap; justify-content: center; gap: 15px; margin: 20px 0; }
.choice {
  font-size: 4rem;
  padding: 15px;
  background: white;
  border-radius: 16px;
  border: 3px solid #90caf9;
  cursor: pointer;
  min-width: 100px;
}
.choice:active { transform: scale(0.95); }