/* ══════════════════════════════════════════
   datastructures.css — DS visualization
══════════════════════════════════════════ */

/* ─── DS Canvas ─── */
.ds-canvas {
  flex: 1;
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-8);
  overflow: auto;
  position: relative;
  min-height: 0;
}

.ds-canvas-inner {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  flex-wrap: wrap;
  max-width: 100%;
}

/* ─── Stack layout ─── */
.ds-stack-container {
  display: flex;
  flex-direction: column-reverse;
  align-items: center;
  gap: var(--space-2);
  position: relative;
}

.ds-stack-label {
  font-size: 0.65rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-muted);
  margin-top: var(--space-4);
}

.ds-stack-pointer {
  font-size: 0.7rem;
  color: var(--accent);
  margin-left: var(--space-2);
  animation: blink 1s step-end infinite;
}

/* ─── Queue layout ─── */
.ds-queue-container {
  display: flex;
  flex-direction: row;
  align-items: center;
  gap: var(--space-2);
  position: relative;
}

.ds-queue-label {
  font-size: 0.6rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  position: absolute;
  bottom: -24px;
  white-space: nowrap;
}

.ds-queue-label.front {
  left: 0;
  color: var(--color-success);
}
.ds-queue-label.rear {
  right: 0;
  color: var(--color-comparing);
}

/* ─── Linked list layout ─── */
.ds-list-container {
  display: flex;
  flex-direction: row;
  align-items: center;
  gap: 0;
  flex-wrap: wrap;
  row-gap: var(--space-6);
}

/* ─── Generic node ─── */
.ds-node {
  display: flex;
  flex-direction: column;
  align-items: center;
  animation: nodeEnter 0.35s cubic-bezier(0.34, 1.56, 0.64, 1) forwards;
}

.ds-node-cell {
  min-width: 56px;
  height: 56px;
  background: var(--bg-card);
  border: 1.5px solid var(--border-subtle);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
  font-weight: 700;
  color: var(--text-primary);
  position: relative;
  transition: all var(--transition-normal);
  cursor: default;
  padding: 0 var(--space-3);
}

.ds-node-cell:hover {
  border-color: var(--border-accent);
  box-shadow: var(--shadow-accent);
}

.ds-node.top-node .ds-node-cell,
.ds-node.front-node .ds-node-cell {
  border-color: var(--color-success);
  box-shadow: 0 0 12px rgba(0, 210, 150, 0.2);
}

.ds-node.entering .ds-node-cell {
  background: var(--accent-dim);
  border-color: var(--accent);
  animation: highlightFlash 0.5s ease;
}

.ds-node.leaving .ds-node-cell {
  background: rgba(239, 68, 68, 0.1);
  border-color: var(--color-error);
  animation: leaveFlash 0.35s ease forwards;
}

.ds-node-index {
  font-size: 0.58rem;
  color: var(--text-muted);
  margin-top: 4px;
  font-variant-numeric: tabular-nums;
}

/* ─── Linked list node (with pointer section) ─── */
.ll-node {
  display: flex;
  flex-direction: row;
  align-items: center;
  animation: nodeEnter 0.35s cubic-bezier(0.34, 1.56, 0.64, 1) forwards;
}

.ll-node-body {
  display: flex;
  height: 52px;
  border: 1.5px solid var(--border-subtle);
  border-radius: var(--radius-md);
  overflow: hidden;
  transition: border-color var(--transition-normal);
}

.ll-node-body:hover {
  border-color: var(--border-accent);
}

.ll-node-value {
  min-width: 52px;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg-card);
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--text-primary);
  padding: 0 var(--space-3);
  border-right: 1px solid var(--border-subtle);
}

.ll-node-pointer {
  width: 36px;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg-elevated);
  color: var(--text-muted);
  font-size: 0.7rem;
}

.ll-arrow {
  display: flex;
  align-items: center;
  color: var(--border-strong);
  font-size: 1.2rem;
  padding: 0 4px;
  user-select: none;
}

.ll-null {
  font-size: 0.75rem;
  color: var(--text-muted);
  padding: 0 var(--space-2);
  font-style: italic;
}

.ll-node.head-node .ll-node-body {
  border-color: var(--color-success);
}
.ll-node.tail-node .ll-node-body {
  border-color: var(--color-comparing);
}

.ll-node.entering .ll-node-body {
  border-color: var(--accent);
  animation: highlightFlash 0.5s ease;
}

.ll-node.leaving .ll-node-body {
  border-color: var(--color-error);
  animation: leaveFlash 0.35s ease forwards;
}

/* ─── Empty state ─── */
.ds-empty {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-3);
  color: var(--text-muted);
}

.ds-empty-icon {
  font-size: 2.5rem;
  opacity: 0.3;
}

.ds-empty-text {
  font-size: 0.78rem;
  letter-spacing: 0.05em;
}

/* ─── Node labels (HEAD, TOP, etc.) ─── */
.node-badge {
  font-size: 0.55rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  padding: 1px 6px;
  border-radius: 2px;
  margin-bottom: 4px;
}

.node-badge.top {
  background: rgba(0, 210, 150, 0.15);
  color: var(--color-success);
}
.node-badge.head {
  background: rgba(0, 210, 150, 0.15);
  color: var(--color-success);
}
.node-badge.tail {
  background: rgba(245, 158, 11, 0.15);
  color: var(--color-comparing);
}
.node-badge.front {
  background: rgba(0, 210, 150, 0.15);
  color: var(--color-success);
}
.node-badge.rear {
  background: rgba(245, 158, 11, 0.15);
  color: var(--color-comparing);
}