#birthday-tool * { box-sizing:border-box; font-size:18px; line-height:1.9; }
#birthday-tool { max-width:680px; margin:30px auto; padding:0 12px; }

#birthday-tool .card{
  background:#fff; padding:26px; border-radius:18px;
  box-shadow:0 6px 25px rgba(0,0,0,.1);
}

#birthday-tool h2{ font-size:22px; margin:0 0 18px; text-align:center; color:#333; }

#birthday-tool .row{ display:flex; gap:14px; margin-bottom:18px; }
#birthday-tool select{
  flex:1; padding:14px 12px; border:1px solid #ccc; border-radius:8px;
}

#birthday-tool .btn{
  width:100%; padding:18px; border:none; border-radius:10px;
  background:#0066cc; color:#fff; font-weight:700; cursor:pointer;
}
#birthday-tool .btn:hover{ background:#0055aa; }

#birthday-tool .result{
  display:none; margin-top:20px; padding:18px; border-radius:12px;
  background:#f8f9fa; border-left:6px solid #0066cc;
  white-space:pre-line;
}
#birthday-tool .hl{ color:#0066cc; font-weight:800; font-size:20px; }

@media (max-width:480px){
  #birthday-tool .row{ flex-direction:column; }
}