:root {
  --bg: #f3f6fb;
  --card: #fff;
  --blue: #157efb;
  --ok: #16a34a;
  --err: #ef4444;
}
* { box-sizing: border-box; }
body {
  background: var(--bg);
  font-family: SolaimanLipi, Inter, Arial, sans-serif;
  margin: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  padding: 20px;
}
.card {
  background: var(--card);
  width: 100%;
  max-width: 720px;
  border-radius: 12px;
  padding: 24px;
  box-shadow: 0 8px 30px rgba(10,20,40,0.08);
}
h1 {
  margin: 0 0 12px;
  font-size: 22px;
  text-align: center;
}
.row {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  justify-content: center;
  margin: 10px 0;
}
.btn {
  background: var(--blue);
  color: #fff;
  border: none;
  padding: 10px 16px;
  border-radius: 10px;
  cursor: pointer;
  font-weight: 600;
}
.btn.secondary {
  background: #e6eefc;
  color: var(--blue);
}
.btn.small {
  padding: 8px 12px;
  font-size: 15px;
  border-radius: 8px;
}
#question {
  text-align: center;
  font-size: 26px;
  margin: 18px 0;
  font-weight: 700;
}
input[type="text"] {
  width: 100%;
  padding: 16px;
  font-size: 18px;
  border: 1px solid #ccd9f1;
  border-radius: 8px;
  text-align: center;
  margin-bottom: 12px;
}
.result {
  text-align: center;
  font-weight: 700;
  min-height: 1.2em;
}
.steps {
  margin-top: 8px;
  text-align: center;
  color: #334155;
  font-weight: 600;
  min-height: 1.2em;
}
.note {
  font-size: 13px;
  color: #475569;
  text-align: center;
  margin-top: 12px;
}
@media(max-width:480px) {
  .row { gap: 6px; }
}