/* Layered-stack kit (stk-*) — a reusable "request descends top→down through
   layers" visual language. Bands (.stk-layer) joined by the shared .mod-conn
   connector; each carries decision blocks (.stk-dec); an optional sticky side
   channel (.stk-side) runs a parallel path. Per-page layer accents are driven
   by one custom property — set --lc on a .stk-layer--* preset (presets live in
   the consuming module's sheet, e.g. auth.css). Wider canvas via .page--wide.
   Decision blocks are static (not links) — no hover affordance.
   Loaded on top of module.css by pages that use the stack.
   Placement convention: docs/architecture/README.md §Styling. */

.stk-stage {
  display: grid;
  grid-template-columns: 1fr 280px;
  gap: 1.4rem;
  align-items: start;
}

/* Solo stage — no side channel: drop the reserved side column and center the
   stack on the canvas instead of leaving it pinned left under empty space. */
.stk-stage--solo {
  grid-template-columns: minmax(0, 1fr);
  justify-items: center;
}

.stk-stage--solo .stk-stack {
  width: 100%;
  max-width: 920px;
}

.stk-stack {
  display: flex;
  flex-direction: column;
}

/* Landing highlight for the cross-linked layers, reusing the
   .section:target keyframes without .section's block margin */
/* Compact targets land in the upper third of the viewport — the eye's
   natural landing zone — with context above still visible. */
.stk-layer[id],
.stk-side__chan[id],
.stk-dec[id] {
  scroll-margin-top: 28vh;
}

.stk-layer:target,
.stk-side__chan:target,
.stk-dec:target {
  animation: target-highlight 2.6s ease-out;
}

@media (prefers-reduced-motion: reduce) {
  .stk-layer:target,
  .stk-side__chan:target,
  .stk-dec:target {
    animation: none;
    box-shadow: 0 0 0 2px var(--accent-muted);
  }
}

/* A prose paragraph can also be a cross-link target (e.g. a sub-topic anchored
   inside a .section). Give it the same landing flash, with the section's own
   scroll-margin so it isn't glued to the viewport top. */
.desc[id] {
  scroll-margin-top: 1rem;
}

.desc[id]:target {
  border-radius: var(--radius-md);
  animation: target-highlight 2.6s ease-out;
}

@media (prefers-reduced-motion: reduce) {
  .desc[id]:target {
    animation: none;
    box-shadow: 0 0 0 2px var(--accent-muted);
  }
}

/* ── Layer band ── */
.stk-layer {
  background: var(--paper);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--card-shadow);
  overflow: hidden;
}

.stk-layer__bar {
  display: flex;
  align-items: center;
  gap: 0.7rem;
  flex-wrap: wrap;
  padding: 0.7rem 1.1rem;
  border-left: 6px solid var(--stk-lc, var(--accent));
  background: var(--stk-lc-pale, var(--tint-6));
}

.stk-layer__n {
  flex: 0 0 auto;
  width: 1.7rem;
  height: 1.7rem;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-family: var(--mono);
  font-size: 0.74rem;
  font-weight: 700;
  color: var(--stk-lc, var(--accent));
  background: var(--paper);
  border: 1.5px solid var(--stk-lc, var(--accent));
  border-radius: 50%;
}

.stk-layer__name {
  font-size: 1.12rem;
  font-weight: 700;
  letter-spacing: var(--heading-spacing);
}

.stk-layer__role {
  margin-left: auto;
  max-width: 38ch;
  font-size: 0.78rem;
  font-style: italic;
  color: var(--text-dim);
  text-align: right;
}

.stk-layer__body {
  display: flex;
  flex-wrap: wrap;
  gap: var(--grid-gap);
  padding: 0.9rem 1.1rem 1.05rem;
}

/* ── Decision block (one inventory item) ── */
.stk-dec {
  flex: 1 1 220px;
  min-width: 200px;
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  padding: 0.7rem 0.8rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
}

.stk-dec--wide {
  flex-basis: 320px;
}
.stk-dec--full {
  flex-basis: 100%;
}

/* ── Warning variant — an implementation caveat to revisit during testing,
   not a settled decision. Amber accent (--s4) reads as caution inside the
   warm palette; the ⚠ marker is owned by the variant, not the markup. ── */
.stk-dec--warn {
  background: var(--s4-pale);
  border-color: var(--s4-glow);
  border-left: var(--border-w) solid var(--s4);
}

.stk-dec--warn .stk-dec__h::before {
  content: "⚠";
  font-size: 0.95rem;
  line-height: 1;
  color: var(--s4);
}

.stk-dec--warn .stk-dec__t {
  color: var(--s4);
}

.stk-dec__h {
  display: flex;
  align-items: center;
  gap: 0.45rem;
  flex-wrap: wrap;
}

.stk-dec__t {
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--text);
  line-height: 1.25;
}

.stk-dec__d {
  font-size: 0.78rem;
  color: var(--text-dim);
  line-height: 1.45;
}

.stk-dec__cols {
  display: flex;
  gap: 0.8rem;
  flex-wrap: wrap;
}

.stk-dec__list {
  margin: 0;
  padding: 0;
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.18rem;
}

.stk-dec__list li {
  position: relative;
  padding-left: 0.85rem;
}

.stk-dec__list li::before {
  content: "";
  position: absolute;
  left: 0.1rem;
  top: 0.55em;
  width: 4px;
  height: 4px;
  border-radius: 50%;
  background: var(--text-dim);
}

.stk-dec details {
  font-size: 0.76rem;
  color: var(--text-dim);
}

.stk-dec summary {
  user-select: none;
  font-size: 0.74rem;
  font-weight: 600;
  color: var(--accent);
}

.stk-dec summary::before {
  content: "▸ ";
}

.stk-dec details[open] summary::before {
  content: "▾ ";
}

.stk-dec details > div {
  margin-top: 0.3rem;
  line-height: 1.5;
}

/* ── Side channel (a parallel path beside the stack) ── */
.stk-side__chan {
  padding: 0.8rem 0.9rem 1rem;
  background: var(--s4-pale);
  border: 1px dashed var(--s4);
  border-radius: var(--radius);
  box-shadow: var(--card-shadow);
}

.stk-side__chan + .stk-side__chan {
  margin-top: 1rem;
}

.stk-side__head {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.stk-side__name {
  font-size: 1rem;
  font-weight: 700;
  color: var(--s4);
  letter-spacing: var(--heading-spacing);
}

.stk-side__tag {
  display: block;
  margin-top: 0.1rem;
  font-family: var(--mono);
  font-size: 0.62rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--s4);
}

.stk-side__xrefs {
  display: flex;
  flex-wrap: wrap;
  gap: 0.3rem;
  margin-top: 0.35rem;
}

.stk-side__flow {
  margin: 0.55rem 0 0.7rem;
  padding: 0.4rem 0.5rem;
  font-family: var(--mono);
  font-size: 0.66rem;
  color: var(--text-dim);
  text-align: center;
  background: var(--paper);
  border: 1px solid var(--border);
  border-radius: 6px;
}

.stk-side__flow b {
  color: var(--s4);
}

.stk-side__decs {
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
}

.stk-side__decs .stk-dec {
  flex: none;
  min-width: 0;
  background: var(--paper);
}

.stk-side__into {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  margin-top: 0.7rem;
  font-family: var(--mono);
  font-size: 0.64rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--s4);
}

.stk-side__into::before,
.stk-side__into::after {
  content: "";
  flex: 1;
  height: 1px;
  background: var(--s4);
  opacity: 0.4;
}

.stk-side__merge {
  margin-top: 0.35rem;
  font-size: 0.7rem;
  font-style: italic;
  color: var(--text-dim);
  text-align: center;
}

@media (max-width: 880px) {
  .stk-stage {
    grid-template-columns: 1fr;
  }
  .stk-layer__role {
    display: none;
  }
}