* { box-sizing: border-box; margin: 0; padding: 0; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang HK", sans-serif;
  background: #e0f7fa;
  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: #00bcd4;
  color: white;
  border: none;
  border-radius: 12px;
  padding: 14px 22px;
  font-size: 1.2rem;
  min-height: 50px;
  cursor: pointer;
}
#items { display: flex; flex-wrap: wrap; justify-content: center; gap: 15px; margin: 20px 0; }
.item {
  font-size: 3rem;
  padding: 20px;
  background: white;
  border-radius: 16px;
  border: 3px solid #80deea;
  cursor: pointer;
  min-width: 100px;
}