html,body{height:100%;margin:0;font-family:system-ui,Arial}
body{
  background:url("back.jpg") center/cover no-repeat fixed;
  display:grid;place-items:center;padding:16px;
}
.box{
  background:white;
  padding:16px;border-radius:12px;max-width:420px;width:100%;
  box-shadow:0 6px 20px rgba(0,0,0,.15);text-align:center;
}
h1{margin:0 0 10px;font-size:20px}
.row{display:flex;gap:8px;justify-content:center;margin:8px 0}
input{width:90px;padding:8px;border:1px solid #ccc;border-radius:8px}
button{padding:8px 14px;border-radius:8px;border:1px solid #2f9e44;background:#2f9e44;color:#fff;cursor:pointer}
button:disabled{opacity:.6;cursor:default}
.out{font:700 34px/1 monospace;margin:6px 0 10px}