* { box-sizing: border-box; margin: 0; padding: 0; }
body { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang HK", sans-serif; background: #f1f8e9; 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: 20px; }
h1 { font-size: 1.6rem; }
.big-btn { background: #8bc34a; color: white; border: none; border-radius: 12px; padding: 16px 24px; font-size: 1.3rem; min-height: 56px; cursor: pointer; margin: 5px; }
#num { font-size: 6rem; background: white; border-radius: 20px; padding: 20px; margin: 20px 0; border: 4px solid #c5e1a5; }