.ex-board {
  margin: 1rem auto 1.25rem;
  max-width: 36rem;
  text-align: center;
}

.ex-equation {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 0.35rem 0.45rem;
  margin: 0.25rem 0 1rem;
  min-height: 3.2rem;
}

.ex-token {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 2.6rem;
  min-height: 2.8rem;
  padding: 0.35rem 0.7rem;
  border: 1px solid var(--color-border, #c5d4e0);
  border-radius: 8px;
  background: var(--color-surface, #fff);
  font-size: clamp(1.5rem, 4vw, 2.1rem);
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  line-height: 1;
  cursor: pointer;
}

.ex-token:hover:not(:disabled) {
  border-color: var(--color-primary, #2a6f97);
  background: #ecfeff;
}

.ex-token:focus-visible {
  outline: 2px solid var(--color-primary, #2a6f97);
  outline-offset: 2px;
}

.ex-token:disabled {
  cursor: default;
  opacity: 1;
}

.ex-token.is-op,
.ex-token.is-eq {
  border-color: transparent;
  background: transparent;
  cursor: default;
  min-width: 1.6rem;
  font-weight: 600;
  opacity: 0.85;
}

.ex-token.is-selected {
  border-color: var(--color-primary, #2a6f97);
  background: #ecfeff;
  box-shadow: 0 0 0 2px #ecfeff;
}

.ex-equation.is-wait-sign .ex-token:not(.is-selected) {
  opacity: 0.7;
}

.ex-token.is-bad {
  background: var(--color-danger-bg, #fee2e2);
  border-color: #dc2626;
}

.ex-workspace {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  min-height: 3rem;
  margin: 0.5rem 0 1rem;
  font-size: clamp(1.45rem, 3.8vw, 2rem);
  font-weight: 700;
  font-variant-numeric: tabular-nums;
}

.ex-workspace-x {
  opacity: 0.9;
}

.ex-slot {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 2.4rem;
  min-height: 2.5rem;
  padding: 0.2rem 0.45rem;
  border-bottom: 2px solid var(--color-border, #c5d4e0);
}

.ex-slot.is-empty {
  color: #94a3b8;
  min-width: 2.8rem;
}

.ex-slot.is-answer {
  border-bottom-color: #2d6a4f;
  color: #2d6a4f;
  min-width: 2.8rem;
}

.ex-ops {
  display: flex;
  flex-wrap: wrap;
  gap: 0.65rem;
  justify-content: center;
  margin: 0.25rem 0 1rem;
}

.ex-op {
  min-width: 3.4rem;
  font-size: 1.6rem;
  font-weight: 700;
  line-height: 1;
  padding: 0.55rem 0.9rem;
  cursor: pointer;
}

.ex-op.is-used {
  outline: 2px solid #2d6a4f;
  outline-offset: 1px;
}

.ex-op:disabled {
  cursor: default;
}

.ex-prompt {
  margin: 0.35rem 0 0.5rem;
  font-size: 1.08rem;
}

.ex-ops.is-wait,
.ex-equation.is-wait-op .ex-token.is-number,
.ex-equation.is-wait-op .ex-token.is-x {
  opacity: 0.55;
}

.ex-ops.is-active .ex-op {
  box-shadow: 0 0 0 2px #ecfeff;
}

.ex-token.is-paren {
  min-width: 1.85rem;
  padding: 0.35rem 0.5rem;
}

.ex-token.is-group-body {
  min-width: 4.2rem;
  font-size: clamp(1.25rem, 3.4vw, 1.75rem);
}

.ex-token.is-zero {
  border-color: transparent;
  background: transparent;
  cursor: default;
}

.ex-flip {
  min-width: 9rem;
  font-size: 1.05rem;
  padding: 0.55rem 1rem;
}

.ex-equation.is-parens {
  max-width: 44rem;
  gap: 0.28rem 0.38rem;
}

.ex-board.is-parens-trace {
  display: grid;
  grid-template-columns: minmax(9rem, 0.4fr) minmax(0, 1fr);
  grid-template-areas:
    "old prev"
    "old current"
    "old workspace"
    "old prompt"
    "old ops";
  column-gap: 1.35rem;
  row-gap: 0.35rem;
  align-items: start;
  text-align: left;
  max-width: 54rem;
  margin-left: 0;
  margin-right: auto;
}

.ex-board.is-parens-trace:not(.has-old) {
  grid-template-columns: minmax(0, 1fr);
  grid-template-areas:
    "prev"
    "current"
    "workspace"
    "prompt"
    "ops";
}

.ex-trace-old {
  grid-area: old;
  display: flex;
  flex-direction: column;
  gap: 0.28rem;
  padding-top: 0.2rem;
}

.ex-trace-old[hidden],
.ex-previous[hidden] {
  display: none !important;
}

.ex-trace-item {
  font-size: 0.95rem;
  font-weight: 600;
  font-variant-numeric: tabular-nums;
  line-height: 1.35;
  color: #64748b;
}

.ex-previous {
  grid-area: prev;
  font-size: clamp(1.35rem, 3.5vw, 1.9rem);
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  line-height: 1.3;
  color: #334155;
  user-select: none;
  min-height: 1.5rem;
}

.ex-board.is-parens-trace .ex-equation {
  grid-area: current;
  justify-content: flex-start;
  margin: 0;
  max-width: none;
}

.ex-board.is-parens-trace .ex-workspace {
  grid-area: workspace;
  justify-content: flex-start;
  margin: 0.15rem 0 0;
}

.ex-board.is-parens-trace .ex-prompt {
  grid-area: prompt;
  text-align: left;
}

.ex-board.is-parens-trace .ex-ops {
  grid-area: ops;
  justify-content: flex-start;
}

@media (max-width: 42rem) {
  .ex-board.is-parens-trace,
  .ex-board.is-parens-trace:not(.has-old) {
    grid-template-columns: minmax(0, 1fr);
    grid-template-areas:
      "old"
      "prev"
      "current"
      "workspace"
      "prompt"
      "ops";
  }
}