/* فونت و متغیرهای پایه */
:root {
  --bg: #f6f8fb;
  --card: #ffffff;
  --text: #1f2937;
  --muted: #6b7280;
  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --error-bg: #fef2f2;
  --error-text: #991b1b;
  --border: #e5e7eb;
  --radius: 12px;
  --shadow: 0 1px 3px rgba(0,0,0,.08), 0 1px 2px rgba(0,0,0,.06);
  --shadow-hover: 0 4px 12px rgba(0,0,0,.1);
  --font: 'Vazirmatn', system-ui, -apple-system, sans-serif;
}

* { box-sizing: border-box; }
html { font-size: 16px; }
body {
  margin: 0;
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
}

.container {
  max-width: 720px;
  margin: 0 auto;
  padding: 24px 16px 40px;
}

header {
  text-align: center;
  margin-bottom: 32px;
}
header h1 {
  margin: 0 0 8px;
  font-size: 2rem;
  font-weight: 700;
  color: var(--primary);
}
.subtitle {
  margin: 0;
  color: var(--muted);
  font-size: 1rem;
}

.card {
  background: var(--card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px;
  margin-bottom: 24px;
  transition: box-shadow .2s;
}
.card:hover { box-shadow: var(--shadow-hover); }
.card h2 {
  margin: 0 0 20px;
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text);
  border-bottom: 1px solid var(--border);
  padding-bottom: 12px;
}

.row { display: flex; gap: 16px; flex-wrap: wrap; }
.fraction-inputs { gap: 24px; }
.fraction-inputs-vertical {
  display: flex;
  flex-direction: column;
  gap: 16px;
}
.fraction-group { flex: 1; min-width: 200px; }
.fraction-group.single { max-width: 360px; }
.fraction-group label {
  display: block;
  font-size: .875rem;
  font-weight: 500;
  color: var(--muted);
  margin-bottom: 6px;
}
.fraction-row {
  display: flex;
  align-items: center;
  gap: 8px;
}
.fraction-row input {
  flex: 1;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-family: inherit;
  font-size: 1rem;
  text-align: center;
  transition: border-color .15s, box-shadow .15s;
}
.fraction-row input:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(37,99,235,.15);
}
.frac-bar {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--muted);
  user-select: none;
}

.two-inputs .input-group { flex: 1; min-width: 180px; }
.input-group label {
  display: block;
  font-size: .875rem;
  font-weight: 500;
  color: var(--muted);
  margin-bottom: 6px;
}
.input-group input {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-family: inherit;
  font-size: 1rem;
  text-align: center;
  transition: border-color .15s, box-shadow .15s;
}
.input-group input:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(37,99,235,.15);
}

.ops {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  margin-top: 16px;
}
.btn {
  padding: 10px 18px;
  border: none;
  border-radius: 8px;
  font-family: inherit;
  font-size: .95rem;
  font-weight: 500;
  cursor: pointer;
  transition: background .15s, transform .05s;
}
.btn:active { transform: scale(.98); }
.btn.primary {
  background: var(--primary);
  color: #fff;
}
.btn.primary:hover { background: var(--primary-hover); }
.btn:not(.primary) {
  background: #eef2ff;
  color: var(--primary);
}
.btn:not(.primary):hover { background: #e0e7ff; }

.result-area {
  margin-top: 16px;
  padding: 16px;
  background: #f0fdf4;
  border-radius: 8px;
  border: 1px solid #bbf7d0;
  animation: fadeIn .2s;
}
@keyframes fadeIn { from { opacity: 0; transform: translateY(-4px); } to { opacity: 1; transform: none; } }
.result-line {
  margin: 6px 0;
  font-size: 1rem;
}
.result-line:first-child { margin-top: 0; }
.result-line:last-child { margin-bottom: 0; }
.result-line span {
  font-family: 'SF Mono', 'Fira Code', monospace;
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--primary);
}
.result-line.decimal { margin-top: 10px; padding-top: 10px; border-top: 1px solid #dcfce7; }
.result-line.decimal span { color: var(--text); font-weight: 500; }

.hint {
  margin: -8px 0 16px;
  font-size: .875rem;
  color: var(--muted);
}

.error {
  margin-top: 12px;
  padding: 12px 14px;
  background: var(--error-bg);
  border: 1px solid #fecaca;
  border-radius: 8px;
  color: var(--error-text);
  font-size: .9rem;
  animation: fadeIn .2s;
}

footer {
  text-align: center;
  margin-top: 32px;
  color: var(--muted);
  font-size: .85rem;
}

/* ریسپانسیو */
@media (max-width: 560px) {
  .fraction-inputs { flex-direction: column; gap: 16px; }
  .ops { justify-content: center; }
}