* { box-sizing: border-box; margin: 0; padding: 0; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang HK", sans-serif;
  background: #fff8e1;
  color: #222;
  padding: 10px;
  max-width: 420px;
  margin: 0 auto;
}
header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 20px; }
h1 { font-size: 1.6rem; }
.big-btn {
  background: #ff9800;
  color: white;
  border: none;
  border-radius: 12px;
  padding: 16px 24px;
  font-size: 1.3rem;
  min-height: 56px;
  cursor: pointer;
}
.coin {
  width: 70px;
  height: 70px;
  border-radius: 50%;
  background: #ffd700;
  border: 4px solid #b8860b;
  font-size: 1.2rem;
  font-weight: bold;
  margin: 8px;
  cursor: pointer;
}
#wallet { display: flex; flex-wrap: wrap; justify-content: center; margin: 20px 0; }
#itemArea { background: white; border-radius: 16px; padding: 30px; text-align: center; font-size: 2rem; margin: 20px 0; }
#paid { font-size: 1.5rem; text-align: center; margin: 15px 0; }
#msg { text-align: center; font-size: 1.4rem; min-height: 2rem; }