:root {
  --card-font-size: 10pt;
  --card-width: 6.5ch;
  --card-padding: 0.2rem;
  --card-cols: 10;
}

body {
  font-family: Arial, sans-serif;
  padding: 2rem;
  background: #fdfdfd;
  color: #222;
}

h1 {
  text-align: center;
  margin-bottom: 1rem;
  font-size: clamp(1.5rem, 3vw, 2.5rem); /* Responsive title scaling */
}

.controls {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  margin-bottom: 1.5rem;
}

.control-row {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  align-items: flex-end;
}

.controls label {
  display: flex;
  flex-direction: column;
  font-size: 0.9rem;
  min-width: 140px;
  gap: 0.25rem;
}

label.disabled {
  opacity: 0.5;
  pointer-events: none;
}


button {
  padding: 0.5rem 1rem;
  font-size: 1rem;
  margin-top: auto;
  cursor: pointer;
}

.cards {
  display: grid;
  grid-template-columns: repeat(var(--card-cols), var(--card-width));
  gap: 0.25rem;
}

.card {
  padding: var(--card-padding);
  text-align: right;
  background: white;
  white-space: pre;
  font-size: var(--card-font-size);
  height: auto;
  position: relative;
}

/* Answer hidden by default */
.card .answer {
  visibility: hidden;
  height: 1em;
  display: block;
  background: white;
}

.card.show-answer .answer {
  visibility: visible;
  background: #dff0d8; /* Light green answer highlight */
}

/* Optional visual note (e.g., for violated constraints) */
.card .note {
  position: absolute;
  top: 0.1em;
  left: 0.2em;
  font-size: 0.9em;
  color: #c00;
}

/* Optional operator-based coloring (add/remove class in JS if needed) */
.card.addition .answer { background: #e0f7fa; }
.card.subtraction .answer { background: #fff3e0; }
.card.multiplication .answer { background: #f3e5f5; }
.card.division .answer { background: #ede7f6; }

.print-note {
  font-size: 0.8rem;
  color: #666;
  margin-top: 1rem;
}

.print-header {
  display: none;
  font-size: 1rem;
  margin-bottom: 1rem;
  justify-content: space-between;
  flex-wrap: wrap;
  border-bottom: 1px dashed #ccc;
  padding-bottom: 0.5rem;
}

@page {
  size: A4 portrait;
  margin: 0.5cm;
}

@media print {
  body {
    padding: 0.5cm;
  }

  .controls,
  .print-note {
    display: none;
  }

  .card {
    padding: 0;
    margin: 0;
    page-break-inside: avoid;
  }

  .cards {
    gap: 0;
  }

  .print-header {
    display: flex;
    font-size: 9pt;
    margin-bottom: 0.25rem;
    padding-bottom: 0.25rem;
  }
}