:root {
  --lm-accent: #0056b3;
  --lm-accent-soft: rgba(0, 86, 179, 0.14);
  --lm-surface: #f7fbff;
  --lm-surface-strong: #eef5ff;
  --lm-border: #d6e1ef;
  --lm-text: #122033;
  --lm-muted: #526173;
  --lm-guide: #9db4d0;
  --lm-shift: #dbe9fb;
  --lm-write: #ffd76a;
  --lm-answer: #0a7a4b;
}

:root.dark {
  --lm-surface: #0f1722;
  --lm-surface-strong: #152234;
  --lm-border: #233247;
  --lm-text: #e5eef8;
  --lm-muted: #b8c5d4;
  --lm-guide: #5c708c;
  --lm-shift: #203048;
  --lm-write: #8a6a00;
  --lm-answer: #5bd49d;
}

.long-multiplication .eyebrow {
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--lm-accent);
  font-weight: 800;
  margin-bottom: 6px;
}

.long-multiplication .long-grid {
  display: grid;
  gap: 16px;
}

.long-multiplication .long-grid.two-col {
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  align-items: start;
}

.long-multiplication .long-field-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 12px;
}

.long-multiplication .long-field,
.long-multiplication .long-options {
  background: var(--lm-surface);
  border: 1px solid var(--lm-border);
  border-radius: 14px;
  padding: 12px;
}

.long-multiplication .long-field .label,
.long-multiplication .long-options .label {
  display: block;
  font-weight: 700;
  color: var(--lm-text);
  margin-bottom: 6px;
}

.long-multiplication .long-options .checkbox {
  display: flex;
  gap: 8px;
  align-items: flex-start;
  margin-top: 8px;
  color: var(--lm-text);
}

.long-multiplication .long-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.long-multiplication .long-actions .button {
  min-width: 120px;
}

.long-multiplication .chip-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.long-multiplication .chip {
  border: 1px solid var(--lm-border);
  background: var(--lm-surface-strong);
  color: var(--lm-text);
  padding: 8px 12px;
  border-radius: 999px;
  font-weight: 700;
  cursor: pointer;
}

.long-multiplication .chip:hover,
.long-multiplication .chip:focus-visible {
  border-color: var(--lm-accent);
  outline: none;
}

.long-multiplication .result-panel {
  background: linear-gradient(180deg, rgba(0, 86, 179, 0.08) 0%, rgba(0, 86, 179, 0.02) 100%);
  border: 1px solid var(--lm-border);
  border-radius: 16px;
  padding: 16px;
  box-shadow: 0 16px 40px rgba(0, 86, 179, 0.12);
}

.long-multiplication .result-value {
  font-size: clamp(2rem, 5vw, 3rem);
  font-weight: 900;
  color: var(--lm-text);
  line-height: 1.1;
  word-break: break-word;
}

.long-multiplication #result-note {
  margin-top: 10px;
  display: grid;
  gap: 6px;
}

.long-multiplication .result-line {
  color: var(--lm-muted);
}

.long-multiplication .check-panel {
  margin-top: 12px;
  display: grid;
  gap: 10px;
  padding: 12px;
  background: rgba(255, 255, 255, 0.7);
  border: 1px solid var(--lm-border);
  border-radius: 14px;
}

.long-multiplication .check-panel__title,
.long-multiplication .check-card__title {
  font-weight: 800;
  color: var(--lm-text);
}

.long-multiplication .check-panel__cards {
  display: grid;
  gap: 10px;
}

.long-multiplication .check-card {
  display: grid;
  gap: 6px;
  padding: 10px;
  background: var(--lm-surface);
  border: 1px solid var(--lm-border);
  border-radius: 12px;
}

.long-multiplication .check-card--approx {
  background: var(--lm-surface-strong);
}

.long-multiplication .check-card__expression {
  font-weight: 700;
  color: var(--lm-text);
  word-break: break-word;
}

.long-multiplication .check-card__note {
  color: var(--lm-muted);
}

.long-multiplication .step-controls {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
  margin: 10px 0;
}

.long-multiplication .layout-shell {
  background: #fff;
  border: 1px solid var(--lm-border);
  border-radius: 14px;
  padding: 12px;
  overflow-x: auto;
}

.long-multiplication .layout-shell .lm-layout {
  min-width: max-content;
}

.long-multiplication .steps-list {
  margin: 0;
  padding-inline-start: 20px;
  display: grid;
  gap: 8px;
}

.long-multiplication .steps-list li {
  background: var(--lm-surface);
  border: 1px solid var(--lm-border);
  border-radius: 10px;
  padding: 8px 10px;
  line-height: 1.6;
}

.long-multiplication .steps-list li.active-step {
  background: var(--lm-accent-soft);
  border-color: var(--lm-accent);
  font-weight: 700;
}

.long-multiplication.is-teacher .check-card,
.long-multiplication.teacher-mode .check-card {
  border-width: 2px;
}

.long-multiplication .input-hint.warning {
  color: #8a5a00;
}

.long-multiplication .lm-layout {
  display: grid;
  gap: 3px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
}

.long-multiplication .lm-row-group {
  display: grid;
  gap: 4px;
}

.long-multiplication .lm-row-group.is-active .lm-row {
  background: rgba(0, 86, 179, 0.04);
  border-radius: 10px;
}

.long-multiplication .lm-row {
  display: grid;
  grid-template-columns: 1.75rem auto;
  align-items: center;
  gap: 8px;
}

.long-multiplication .lm-operator {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 1.75rem;
  font-weight: 800;
  color: var(--lm-text);
}

.long-multiplication .lm-operator--times,
.long-multiplication .lm-operator--plus {
  color: var(--lm-accent);
}

.long-multiplication .lm-digits {
  display: grid;
  grid-template-columns: repeat(var(--lm-cols, 1), minmax(1.8rem, 1.8rem));
  gap: 2px;
}

.long-multiplication .lm-rule {
  border-top: 3px solid var(--lm-text);
  width: calc(var(--lm-cols, 1) * 1.8rem + (var(--lm-cols, 1) - 1) * 2px);
}

.long-multiplication .lm-cell {
  min-height: 1.8rem;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 8px;
  color: var(--lm-text);
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  position: relative;
}

.long-multiplication .has-guides .lm-cell {
  border: 1px dashed var(--lm-guide);
}

.long-multiplication .lm-cell--carry {
  font-size: 0.9rem;
  color: var(--lm-accent);
  font-weight: 800;
}

.long-multiplication .lm-cell--shift-guide {
  background: var(--lm-shift);
}

.long-multiplication .lm-cell--shift-guide::before {
  content: "";
  width: 0.5rem;
  height: 0.5rem;
  border-right: 2px solid var(--lm-guide);
  border-bottom: 2px solid var(--lm-guide);
  transform: rotate(-45deg);
  opacity: 0.9;
}

.long-multiplication .lm-cell--row-active {
  background: rgba(0, 86, 179, 0.06);
}

.long-multiplication .lm-cell--addition {
  background: rgba(10, 122, 75, 0.12);
  outline: 2px solid rgba(10, 122, 75, 0.32);
  outline-offset: -1px;
}

.long-multiplication .lm-cell--write {
  background: rgba(255, 215, 106, 0.45);
  outline: 2px solid rgba(138, 106, 0, 0.7);
  outline-offset: -1px;
}

.long-multiplication .lm-cell--answer {
  color: var(--lm-answer);
}

.long-multiplication .lm-cell.is-active {
  background: var(--lm-accent-soft);
  outline: 2px solid rgba(0, 86, 179, 0.48);
  outline-offset: -1px;
  text-decoration: underline;
  text-underline-offset: 0.12em;
}

.long-multiplication .lm-row-note {
  margin: 0 0 0 calc(1.75rem + 8px);
  padding: 8px 10px;
  border-radius: 10px;
  background: var(--lm-surface);
  border: 1px solid var(--lm-border);
  color: var(--lm-muted);
  font-size: 0.95rem;
  line-height: 1.55;
}

.long-multiplication.is-teacher .layout-shell,
.long-multiplication.teacher-mode .layout-shell,
.long-multiplication .lm-layout.is-teacher {
  border-width: 2px;
}

.long-multiplication.is-teacher .lm-cell,
.long-multiplication.is-teacher .steps-list li,
.long-multiplication.teacher-mode .lm-cell,
.long-multiplication.teacher-mode .steps-list li {
  font-size: 1.05rem;
}

.long-multiplication.is-teacher .lm-row-note,
.long-multiplication.teacher-mode .lm-row-note {
  font-size: 1rem;
  color: var(--lm-text);
  border-width: 2px;
}

@media (min-width: 1080px) {
  .long-multiplication .long-grid.two-col {
    grid-template-columns: minmax(360px, 520px) 1fr;
  }
}