/* prepweave-public-preview v1.2.3 */
:root {
  color-scheme: light;
  --page: #f7f8fb;
  --surface: #ffffff;
  --surface-soft: #f1f3f7;
  --line: #dfe3eb;
  --ink: #171b26;
  --muted: #626b7c;
  --cyan: #087f8d;
  --violet: #6553c8;
  --green: #69dca8;
  --gold: #f4c46f;
  --danger: #b83a4b;
  --code: #f3f5f9;
  --code-ink: #202633;
  --radius: 1.15rem;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  background:
    radial-gradient(circle at 10% 0, rgba(84, 220, 255, 0.08), transparent 30rem),
    radial-gradient(circle at 90% 0, rgba(152, 119, 255, 0.08), transparent 28rem),
    var(--page);
  font: 16px/1.5 ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

a { color: var(--cyan); text-underline-offset: 0.22em; }
a:hover { text-decoration-thickness: 0.13em; }
button, input, select { font: inherit; }

.skip-link {
  position: fixed;
  z-index: 20;
  top: 0.75rem;
  left: 0.75rem;
  padding: 0.65rem 0.85rem;
  color: #07131a;
  background: var(--cyan);
  border-radius: 0.7rem;
  transform: translateY(-180%);
}
.skip-link:focus { transform: translateY(0); }

.site-nav {
  position: sticky;
  z-index: 10;
  top: 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  min-height: 4.25rem;
  padding: 0.65rem max(1.1rem, calc((100vw - 70rem) / 2));
  border-bottom: 1px solid var(--line);
  background: color-mix(in srgb, var(--surface) 92%, transparent);
  backdrop-filter: blur(18px);
}

.site-brand {
  display: flex;
  flex-direction: column;
  color: var(--ink);
  text-decoration: none;
  font-weight: 800;
  line-height: 1.05;
  letter-spacing: -0.025em;
}
.site-brand small {
  margin-top: 0.22rem;
  color: var(--violet);
  font-size: 0.72rem;
  font-weight: 720;
  letter-spacing: 0.02em;
}

.site-links { display: flex; flex-wrap: wrap; align-items: center; gap: 0.55rem 1rem; }
.site-links a { color: var(--muted); text-decoration: none; font-size: 0.9rem; font-weight: 650; }
.site-links a:hover, .site-links a[aria-current="page"] { color: var(--ink); }
.site-links .pro-link { color: #16101f; background: var(--violet); padding: 0.5rem 0.8rem; border-radius: 999px; }

.page-shell { width: min(70rem, calc(100% - 2.2rem)); margin: 0 auto; padding: 3.5rem 0 4rem; }
.hero { max-width: 52rem; margin-bottom: 2.2rem; }
.kicker { margin: 0 0 0.65rem; color: var(--cyan); font-size: 0.76rem; font-weight: 800; letter-spacing: 0.14em; text-transform: uppercase; }
h1, h2, h3 { text-wrap: balance; }
h1 { margin: 0; font-size: clamp(2.45rem, 7vw, 5.4rem); line-height: 0.98; letter-spacing: -0.055em; }
h2 { margin: 2.7rem 0 1rem; font-size: clamp(1.55rem, 3vw, 2.25rem); line-height: 1.12; letter-spacing: -0.035em; }
h3 { margin: 0; font-size: 1.12rem; line-height: 1.25; letter-spacing: -0.018em; }
.lede { max-width: 46rem; margin: 1.15rem 0 0; color: var(--muted); font-size: clamp(1rem, 2vw, 1.18rem); }

.notice {
  margin: 1.4rem 0;
  padding: 1rem 1.1rem;
  border: 1px solid color-mix(in srgb, var(--gold) 55%, var(--line));
  border-radius: 0.9rem;
  color: color-mix(in srgb, var(--ink) 82%, #7c4a00);
  background: color-mix(in srgb, var(--gold) 16%, var(--surface));
}
.notice strong { color: var(--ink); }

.stats, .feature-grid, .family-grid, .pattern-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.9rem;
}
.stats { margin: 1.8rem 0 0; }
.stat, .feature-card, .family-card, .pattern-card, .catalog-item, .candidate-card, .pro-panel {
  min-width: 0;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
}
.stat { padding: 1.15rem; }
.stat strong { display: block; font-size: 1.55rem; letter-spacing: -0.035em; }
.stat span { color: var(--muted); font-size: 0.86rem; }

.feature-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.feature-card, .family-card, .pattern-card { padding: 1.2rem; }
.feature-card p, .family-card p, .pattern-card p { margin: 0.55rem 0 0; color: var(--muted); }
.feature-card .actions, .family-card .actions, .pattern-card .actions { margin-top: 1rem; }

.family-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.family-card { position: relative; min-height: 9.5rem; }
.family-card.is-locked { opacity: 0.78; }

.membership {
  display: inline-flex;
  align-items: center;
  width: fit-content;
  margin-bottom: 0.72rem;
  padding: 0.27rem 0.58rem;
  border-radius: 999px;
  font-size: 0.72rem;
  font-weight: 800;
  letter-spacing: 0.045em;
  text-transform: uppercase;
}
.membership.free { color: #062815; background: var(--green); }
.membership.pro { color: #1c1230; background: var(--violet); }
.membership.candidate { color: #2d1b00; background: var(--gold); }

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 2.75rem;
  padding: 0.62rem 0.95rem;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--ink);
  background: var(--surface-soft);
  text-decoration: none;
  font-weight: 720;
}
.button.primary { color: #07131a; border-color: transparent; background: var(--cyan); }
.button.pro { color: #171020; border-color: transparent; background: var(--violet); }

.catalog-controls {
  position: relative;
  display: grid;
  grid-template-columns: minmax(15rem, 2fr) repeat(3, minmax(8rem, 0.65fr));
  gap: 0.8rem;
  margin: 1.5rem 0 1rem;
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
}
.control { display: grid; gap: 0.38rem; color: var(--muted); font-size: 0.78rem; font-weight: 700; }
.control input, .control select {
  width: 100%;
  min-height: 2.65rem;
  padding: 0.55rem 0.7rem;
  border: 1px solid var(--line);
  border-radius: 0.7rem;
  color: var(--ink);
  background: var(--surface);
}
.control input:focus, .control select:focus { outline: 2px solid var(--cyan); outline-offset: 2px; }
.search-control { position: relative; }
.suggestions {
  position: absolute;
  z-index: 6;
  top: calc(100% + 0.25rem);
  right: 0;
  left: 0;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 0.8rem;
  background: var(--surface);
  box-shadow: 0 1.1rem 2.5rem color-mix(in srgb, var(--ink) 14%, transparent);
}
.suggestions button { display: block; width: 100%; padding: 0.72rem; border: 0; border-bottom: 1px solid var(--line); color: var(--ink); background: transparent; text-align: left; }
.suggestions button:hover, .suggestions button:focus { background: var(--surface-soft); }

.catalog-status { display: flex; align-items: center; justify-content: space-between; gap: 1rem; margin: 0.9rem 0; color: var(--muted); }
.catalog-grid { display: grid; gap: 0.65rem; }
.catalog-item { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 1rem; padding: 1rem; }
.catalog-item-main { min-width: 0; }
.catalog-item-title { display: inline; color: var(--ink); font-size: 1rem; font-weight: 760; text-decoration: none; }
.catalog-item-title:hover { color: var(--cyan); }
.catalog-template-tags { display: flex; flex-wrap: wrap; gap: .38rem; margin-top: .55rem; }
.catalog-template-tag { text-decoration: none; }
.catalog-meta { margin: 0.32rem 0 0; color: var(--muted); font-size: 0.84rem; overflow-wrap: anywhere; }
.catalog-teaser { margin: 0.5rem 0 0; color: var(--ink); font-size: 0.9rem; }
.catalog-item-side { display: flex; flex-direction: column; align-items: flex-end; justify-content: center; gap: 0.45rem; }
.catalog-item-side small { color: var(--muted); text-align: right; }

.pagination { display: flex; flex-wrap: wrap; align-items: center; justify-content: center; gap: 0.55rem; margin-top: 1.2rem; }
.pagination button { min-height: 2.5rem; padding: 0.45rem 0.8rem; border: 1px solid var(--line); border-radius: 0.65rem; color: var(--ink); background: var(--surface); }
.pagination button:disabled { opacity: 0.38; }
.pagination span { color: var(--muted); }

.pattern-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.pattern-card dl { margin: 0.9rem 0 0; }
.pattern-card dt { margin-top: 0.7rem; color: var(--cyan); font-size: 0.74rem; font-weight: 800; letter-spacing: 0.07em; text-transform: uppercase; }
.pattern-card dd { margin: 0.2rem 0 0; color: var(--muted); }
.pattern-card pre { width: 100%; max-width: 100%; overflow: auto; max-height: 18rem; padding: 0.9rem; border: 1px solid var(--line); border-radius: 0.75rem; color: var(--code-ink); background: var(--code); font-size: 0.83rem; }
.pattern-card pre code { color: inherit; background: transparent; }

.graph-board { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 0.8rem; margin: 1.4rem 0; }
.graph-node { min-height: 8rem; padding: 1rem; border: 1px solid rgba(118, 228, 247, 0.35); border-radius: 1rem; background: rgba(118, 228, 247, 0.075); }
.graph-node span { display: block; margin-top: 0.5rem; color: var(--muted); font-size: 0.82rem; }
.edge-list { display: flex; flex-wrap: wrap; gap: 0.55rem; padding: 0; list-style: none; }
.edge-list li { padding: 0.5rem 0.7rem; border: 1px solid var(--line); border-radius: 999px; color: var(--muted); background: var(--surface); font-size: 0.82rem; }

.problem-header { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 1rem; align-items: start; }
.problem-id { color: var(--cyan); font-size: 0.95rem; font-weight: 800; letter-spacing: 0.08em; }
.tag-list { display: flex; flex-wrap: wrap; gap: 0.4rem; margin-top: 0.8rem; }
.tag-list span { padding: 0.3rem 0.55rem; border-radius: 999px; color: var(--muted); background: var(--surface-soft); font-size: 0.78rem; }
.candidate-list { display: grid; gap: 0.75rem; }
.candidate-card { padding: 1.05rem; }
.candidate-card header { display: flex; align-items: flex-start; justify-content: space-between; gap: 0.8rem; }
.candidate-card p { margin: 0.6rem 0 0; color: var(--muted); }
.candidate-card .actions { margin-top: 0.8rem; }

.pro-panel { max-width: 46rem; padding: clamp(1.25rem, 4vw, 2.2rem); }
.pro-panel h1 { font-size: clamp(2.25rem, 6vw, 4.8rem); }
.pro-panel .product-subtitle { margin: 0.75rem 0 1.3rem; color: var(--violet); font-size: 1.35rem; font-weight: 750; }

.visually-hidden { position: absolute !important; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
.page-footer { margin-top: 3.5rem; padding-top: 1.25rem; border-top: 1px solid var(--line); color: var(--muted); font-size: 0.84rem; }

@media (max-width: 850px) {
  .stats, .family-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .catalog-controls { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .search-control { grid-column: 1 / -1; }
  .graph-board { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (max-width: 620px) {
  .site-nav { position: static; align-items: flex-start; }
  .site-links { justify-content: flex-end; }
  .site-links a:not(.pro-link) { display: none; }
  .page-shell { width: min(100% - 1.25rem, 70rem); padding-top: 2.25rem; }
  .stats, .feature-grid, .family-grid, .pattern-grid, .graph-board { grid-template-columns: minmax(0, 1fr); }
  .catalog-controls { grid-template-columns: 1fr; }
  .search-control { grid-column: auto; }
  .catalog-item { grid-template-columns: 1fr; }
  .catalog-item-side { align-items: flex-start; }
  .catalog-item-side small { text-align: left; }
  .problem-header { grid-template-columns: 1fr; }
}

/* Free problem library --------------------------------------------------- */
.page-shell:has(.free-problem-library) {
  width: min(92rem, calc(100% - 1.4rem));
  padding-top: 1rem;
}

.free-problem-library {
  --library-soft: color-mix(in srgb, var(--ink) 4%, var(--surface));
  --library-hover: color-mix(in srgb, var(--cyan) 8%, var(--surface));
  --library-selected: color-mix(in srgb, var(--cyan) 13%, var(--surface));
  min-height: calc(100vh - 7rem);
  color: var(--ink);
}

.free-problem-library button,
.free-problem-library input,
.free-problem-library select,
.free-problem-library summary { font: inherit; }

.free-problem-library button:focus-visible,
.free-problem-library input:focus-visible,
.free-problem-library select:focus-visible,
.free-problem-library summary:focus-visible,
.free-problem-library a:focus-visible {
  outline: 3px solid color-mix(in srgb, var(--cyan) 68%, transparent);
  outline-offset: 2px;
}

.problem-library-toolbar {
  position: sticky;
  z-index: 8;
  top: 4.45rem;
  display: grid;
  grid-template-columns: minmax(12rem, 18rem) minmax(20rem, 1fr) auto;
  gap: 0.45rem 0.8rem;
  align-items: center;
  padding: 0.75rem;
  border: 1px solid var(--line);
  border-radius: 0.9rem 0.9rem 0 0;
  background: color-mix(in srgb, var(--surface) 94%, transparent);
  backdrop-filter: blur(16px);
}

body:has(.ps-app-shell) .problem-library-toolbar { top: 0; }

.problem-library-heading { min-width: 0; }
.problem-library-heading .kicker { margin-bottom: 0.22rem; }
.problem-library-heading p:last-child {
  margin: 0;
  color: var(--muted);
  font-size: 0.74rem;
  line-height: 1.35;
}

.problem-library-search {
  position: relative;
  display: grid;
  grid-template-columns: 2.2rem minmax(0, 1fr) 2.25rem;
  align-items: center;
  min-height: 3.1rem;
  border: 1px solid transparent;
  border-radius: 1.6rem;
  background: var(--surface-soft);
  box-shadow: var(--ps-shadow-sm, 0 1px 2px rgb(20 26 40 / 6%));
}

.problem-library-search:focus-within {
  border-color: color-mix(in srgb, var(--cyan) 48%, var(--line));
  background: var(--surface);
  box-shadow: var(--ps-shadow, 0 0.8rem 2.5rem rgb(20 26 40 / 10%));
}

.search-glyph {
  display: grid;
  place-items: center;
  color: var(--muted);
  font-size: 1.3rem;
}

.problem-library-search input {
  width: 100%;
  min-width: 0;
  min-height: 3rem;
  padding: 0.55rem 0.2rem;
  border: 0;
  outline: 0;
  color: var(--ink);
  background: transparent;
}

.problem-library-search input::placeholder { color: var(--muted); opacity: 1; }
.problem-library-search .search-clear {
  width: 2rem;
  min-height: 2rem;
  padding: 0;
  border: 0;
  border-radius: 999px;
  color: var(--muted);
  background: transparent;
  cursor: pointer;
  font-size: 1.25rem;
}
.problem-library-search .search-clear:hover { color: var(--ink); background: var(--library-hover); }

.problem-library-toolbar .search-hint {
  grid-column: 2;
  margin: 0 0.55rem;
  color: var(--muted);
  font-size: 0.7rem;
}

.problem-library-advanced { position: relative; align-self: stretch; }
.problem-library-advanced > summary {
  display: inline-flex;
  min-height: 3.1rem;
  padding: 0.55rem 0.8rem;
  align-items: center;
  gap: 0.4rem;
  border: 1px solid var(--line);
  border-radius: 0.72rem;
  color: var(--muted);
  background: var(--surface);
  cursor: pointer;
  font-size: 0.78rem;
  font-weight: 720;
  list-style: none;
  white-space: nowrap;
}
.problem-library-advanced > summary::-webkit-details-marker { display: none; }
.problem-library-advanced[open] > summary,
.problem-library-advanced > summary:hover { color: var(--cyan); border-color: var(--cyan); }
.advanced-count {
  display: inline-flex;
  min-width: 1.25rem;
  height: 1.25rem;
  align-items: center;
  justify-content: center;
  border-radius: 999px;
  color: #fff;
  background: var(--cyan);
  font-size: 0.65rem;
}

.problem-library-advanced .advanced-panel {
  position: absolute;
  z-index: 30;
  top: calc(100% + 0.45rem);
  right: 0;
  display: grid;
  width: min(58rem, calc(100vw - 2rem));
  padding: 0.9rem;
  grid-template-columns: repeat(5, minmax(8.2rem, 1fr)) auto;
  gap: 0.65rem;
  align-items: end;
  border: 1px solid var(--line);
  border-radius: 0.85rem;
  background: var(--surface);
  box-shadow: var(--ps-shadow, 0 1rem 3rem rgb(20 26 40 / 16%));
}
.problem-library-advanced .advanced-panel > p {
  grid-column: 1 / -1;
  margin: 0;
  color: var(--muted);
  font-size: 0.75rem;
}
.problem-library-advanced .advanced-close { display: none; }
.problem-library-advanced label {
  display: grid;
  min-width: 0;
  gap: 0.3rem;
  color: var(--muted);
  font-size: 0.7rem;
  font-weight: 720;
}
.problem-library-advanced input,
.problem-library-advanced select {
  width: 100%;
  min-width: 0;
  min-height: 2.5rem;
  padding: 0.48rem 0.6rem;
  border: 1px solid var(--line);
  border-radius: 0.58rem;
  color: var(--ink);
  background: var(--surface-soft);
}

.free-problem-library .reset-filters,
.free-problem-library .problem-pager button,
.free-problem-library .detail-action,
.free-problem-library .similar-action,
.free-problem-library .mobile-back {
  display: inline-flex;
  min-height: 2.5rem;
  padding: 0.48rem 0.72rem;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--line);
  border-radius: 0.58rem;
  color: var(--ink);
  background: var(--surface);
  cursor: pointer;
  font-weight: 720;
  text-decoration: none;
}
.free-problem-library .reset-filters:hover,
.free-problem-library .problem-pager button:hover:not(:disabled),
.free-problem-library .detail-action:hover,
.free-problem-library .similar-action:hover,
.free-problem-library .mobile-back:hover { color: var(--cyan); border-color: var(--cyan); }

.problem-library-workspace {
  display: grid;
  min-height: calc(100vh - 12rem);
  grid-template-columns: minmax(19rem, 23rem) minmax(0, 1fr);
  border: 1px solid var(--line);
  border-top: 0;
  border-radius: 0 0 0.9rem 0.9rem;
  background: var(--surface);
  overflow: hidden;
}

.free-problem-library .problem-master {
  display: grid;
  min-width: 0;
  grid-template-rows: auto minmax(0, 1fr) auto;
  border-right: 1px solid var(--line);
  background: color-mix(in srgb, var(--surface) 97%, var(--ink));
}

.free-problem-library .master-status {
  display: flex;
  min-height: 2.6rem;
  padding: 0.55rem 0.72rem;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  border-bottom: 1px solid var(--line);
  color: var(--muted);
  font-size: 0.72rem;
}
.free-problem-library .master-status strong { color: var(--ink); font-variant-numeric: tabular-nums; }
.free-problem-library .scope-filter {
  min-height: 1.65rem;
  margin-left: 0.45rem;
  padding: 0.18rem 0.48rem;
  border: 1px solid color-mix(in srgb, var(--cyan) 42%, var(--line));
  border-radius: 999px;
  color: var(--cyan);
  background: var(--library-hover);
  cursor: pointer;
  font-size: 0.66rem;
  font-weight: 760;
}
.free-problem-library .scope-filter::after { margin-left: 0.3rem; content: "×"; }

.free-problem-library .problem-list {
  min-height: 0;
  max-height: calc(100vh - 15rem);
  padding: 0;
  margin: 0;
  overflow-y: auto;
  list-style: none;
  scrollbar-gutter: stable;
}
.free-problem-library .problem-row {
  position: relative;
  display: grid;
  width: 100%;
  min-height: 4.25rem;
  padding: 0.66rem 0.72rem 0.66rem 0.85rem;
  gap: 0.35rem;
  border: 0;
  border-bottom: 1px solid var(--line);
  color: var(--ink);
  background: transparent;
  text-align: left;
  text-decoration: none;
  cursor: pointer;
  content-visibility: auto;
  contain-intrinsic-size: auto 4.25rem;
}
.free-problem-library .problem-row::before {
  position: absolute;
  inset: 0 auto 0 0;
  width: 0.2rem;
  background: transparent;
  content: "";
}
.free-problem-library .problem-row:hover { background: var(--library-hover); }
.free-problem-library .problem-row[aria-current="true"] { background: var(--library-selected); }
.free-problem-library .problem-row[aria-current="true"]::before { background: var(--cyan); }
.free-problem-library .problem-row-heading {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 0.5rem;
  align-items: baseline;
}
.free-problem-library .problem-row-title {
  min-width: 0;
  font-size: 0.86rem;
  font-weight: 680;
  line-height: 1.3;
  overflow-wrap: anywhere;
}
.free-problem-library .problem-row-meta,
.free-problem-library .chip-row {
  display: flex;
  min-width: 0;
  flex-wrap: wrap;
  gap: 0.3rem;
  align-items: center;
}
.free-problem-library .membership { margin: 0; flex: none; }
.free-problem-library .problem-row .membership { padding: 0.16rem 0.4rem; font-size: 0.6rem; }
.free-problem-library .tag-chip,
.free-problem-library .template-token {
  display: inline-flex;
  min-height: 1.55rem;
  padding: 0.18rem 0.44rem;
  align-items: center;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--muted);
  background: var(--surface-soft);
  font-size: 0.66rem;
  line-height: 1.15;
  overflow-wrap: anywhere;
}
.free-problem-library .template-token {
  border-color: var(--ps-template-0-line, #9ebce7);
  color: var(--ps-template-0, #275fae);
  background: var(--ps-template-0-soft, #e9f2ff);
  font-weight: 740;
}
.free-problem-library .template-token[data-template-series="1"] { border-color: var(--ps-template-1-line); color: var(--ps-template-1); background: var(--ps-template-1-soft); }
.free-problem-library .template-token[data-template-series="2"] { border-color: var(--ps-template-2-line); color: var(--ps-template-2); background: var(--ps-template-2-soft); }
.free-problem-library .template-token[data-template-series="3"] { border-color: var(--ps-template-3-line); color: var(--ps-template-3); background: var(--ps-template-3-soft); }
.free-problem-library .template-token[data-template-series="4"] { border-color: var(--ps-template-4-line); color: var(--ps-template-4); background: var(--ps-template-4-soft); }
.free-problem-library .template-token[data-template-series="5"] { border-color: var(--ps-template-5-line); color: var(--ps-template-5); background: var(--ps-template-5-soft); }

.free-problem-library .empty-state { padding: 2rem 1rem; color: var(--muted); text-align: center; }
.free-problem-library .problem-pager {
  display: grid;
  min-height: 3.2rem;
  padding: 0.45rem 0.55rem;
  grid-template-columns: auto minmax(0, 1fr) auto;
  gap: 0.45rem;
  align-items: center;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 0.7rem;
  text-align: center;
}
.free-problem-library .problem-pager button { min-height: 2.2rem; padding: 0.35rem 0.55rem; font-size: 0.7rem; }
.free-problem-library .problem-pager button:disabled { opacity: 0.4; cursor: not-allowed; }

.free-problem-library .problem-preview {
  min-width: 0;
  max-height: calc(100vh - 11.5rem);
  padding: clamp(0.9rem, 2.4vw, 1.5rem);
  overflow-y: auto;
  background: var(--surface);
  scrollbar-gutter: stable;
}
.free-problem-library .preview-article { display: grid; max-width: 64rem; margin: 0 auto; gap: 1rem; }
.free-problem-library .preview-header { display: grid; gap: 0.65rem; }
.free-problem-library .mobile-back { display: none; width: fit-content; }
.free-problem-library .preview-eyebrow {
  margin: 0;
  color: var(--cyan);
  font-size: 0.76rem;
  font-weight: 820;
  letter-spacing: 0.07em;
  text-transform: uppercase;
}
.free-problem-library .preview-title {
  margin: 0;
  font-size: clamp(1.75rem, 4vw, 2.75rem);
  line-height: 1.07;
  letter-spacing: -0.038em;
  overflow-wrap: anywhere;
}
.free-problem-library .preview-actions { display: flex; flex-wrap: wrap; gap: 0.5rem; }
.free-problem-library .detail-action.primary { color: #fff; border-color: transparent; background: var(--cyan); }
.free-problem-library .metadata-note { margin: 0; color: var(--muted); font-size: 0.76rem; }

.free-problem-library .content-section {
  --section-tone: var(--ps-template-0, #275fae);
  padding: clamp(0.8rem, 2vw, 1.1rem);
  border: 1px solid color-mix(in srgb, var(--section-tone) 38%, var(--line));
  border-radius: 0.9rem;
  background: color-mix(in srgb, var(--section-tone) 7%, var(--surface));
}
.free-problem-library .content-section.similar-section { --section-tone: var(--ps-template-3, #855600); }
.free-problem-library .content-section.locked-section { --section-tone: var(--violet); }
.free-problem-library .content-section > h2 { margin: 0 0 0.65rem; font-size: 1.2rem; }
.free-problem-library .section-heading { margin-bottom: 0.75rem; }
.free-problem-library .section-heading h2 {
  margin: 0;
  color: color-mix(in srgb, var(--section-tone) 78%, var(--ink));
  font-size: 1.1rem;
}
.free-problem-library .section-heading p { margin: 0.28rem 0 0; color: var(--muted); font-size: 0.76rem; }
.free-problem-library .fold-list { display: grid; gap: 0.55rem; }
.free-problem-library .fold-card {
  border: 1px solid color-mix(in srgb, var(--section-tone) 30%, var(--line));
  border-radius: 0.72rem;
  background: color-mix(in srgb, var(--surface) 92%, var(--section-tone));
  overflow: hidden;
}
.free-problem-library .fold-card > summary {
  display: flex;
  min-height: 3.15rem;
  padding: 0.65rem 0.75rem;
  align-items: center;
  gap: 0.55rem;
  cursor: pointer;
  list-style: none;
}
.free-problem-library .fold-card > summary::-webkit-details-marker { display: none; }
.free-problem-library .fold-card > summary::before {
  flex: none;
  color: var(--muted);
  content: "›";
  font-size: 1.2rem;
  transition: transform 0.15s ease;
}
.free-problem-library .fold-card[open] > summary::before { transform: rotate(90deg); }
.free-problem-library .fold-summary-copy { display: grid; min-width: 0; gap: 0.12rem; }
.free-problem-library .fold-summary-copy strong { line-height: 1.25; overflow-wrap: anywhere; }
.free-problem-library .fold-summary-copy small { color: var(--muted); font-size: 0.68rem; }
.free-problem-library .fold-summary-trailing { display: flex; margin-left: auto; flex: none; gap: 0.3rem; align-items: center; }
.free-problem-library .fold-body {
  display: grid;
  padding: 0.8rem;
  gap: 0.7rem;
  border-top: 1px solid color-mix(in srgb, var(--section-tone) 22%, var(--line));
}
.free-problem-library .explanation-block { display: grid; gap: 0.22rem; }
.free-problem-library .explanation-block h3 {
  margin: 0;
  color: var(--muted);
  font-size: 0.68rem;
  font-weight: 820;
  letter-spacing: 0.055em;
  text-transform: uppercase;
}
.free-problem-library .explanation-block p,
.free-problem-library .locked-copy { margin: 0; line-height: 1.55; overflow-wrap: anywhere; }
.free-problem-library .similar-action { width: fit-content; }
.free-problem-library .no-similar { margin: 0; color: var(--muted); }

@media (max-width: 72rem) {
  .problem-library-toolbar { grid-template-columns: minmax(0, 1fr) auto; }
  .problem-library-heading { display: none; }
  .problem-library-search { grid-column: 1; }
  .problem-library-toolbar .search-hint { grid-column: 1 / -1; grid-row: 2; }
  .problem-library-advanced { grid-column: 2; grid-row: 1; }
  .problem-library-advanced .advanced-panel { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .problem-library-advanced .reset-filters { width: fit-content; }
}

@media (max-width: 56rem) {
  .page-shell:has(.free-problem-library) { width: min(100% - 0.7rem, 92rem); padding-top: 0.35rem; }
  .free-problem-library { min-height: 100vh; }
  .problem-library-toolbar { position: static; padding: 0.6rem; border-radius: 0.78rem 0.78rem 0 0; }
  .problem-library-toolbar .search-hint { display: none; }
  .problem-library-advanced > summary { width: 2.9rem; padding: 0.5rem; justify-content: center; }
  .problem-library-advanced > summary > span:nth-child(2) { display: none; }
  .problem-library-advanced .advanced-panel {
    position: fixed;
    z-index: 40;
    inset: max(0.65rem, env(safe-area-inset-top)) 0.65rem auto;
    width: auto;
    grid-template-columns: 1fr;
    max-height: calc(100vh - 1.3rem - env(safe-area-inset-top));
    overflow-y: auto;
  }
  .problem-library-advanced .advanced-close {
    display: inline-flex;
    width: fit-content;
    min-height: 2.5rem;
    padding: 0.45rem 0.7rem;
    align-items: center;
    justify-self: end;
    gap: 0.35rem;
    border: 1px solid var(--line);
    border-radius: 0.58rem;
    color: var(--ink);
    background: var(--surface);
    cursor: pointer;
    font-weight: 720;
  }
  .problem-library-workspace { display: block; min-height: calc(100vh - 5rem); border-radius: 0 0 0.78rem 0.78rem; }
  .free-problem-library .problem-master { min-height: calc(100vh - 5rem); border-right: 0; }
  .free-problem-library .problem-list { max-height: none; }
  .free-problem-library .problem-preview { display: none; max-height: none; min-height: calc(100vh - 5rem); padding: 0.75rem; overflow: visible; }
  .problem-library-workspace.is-mobile-detail .problem-master { display: none; }
  .problem-library-workspace.is-mobile-detail .problem-preview { display: block; }
  .free-problem-library .mobile-back { display: inline-flex; }
  .free-problem-library .fold-card > summary { min-height: 3.4rem; align-items: flex-start; }
  .free-problem-library .fold-summary-trailing { display: none; }
  .free-problem-library .preview-actions .detail-action { flex: 1 1 10rem; }
}

@media (prefers-reduced-motion: reduce) {
  .free-problem-library * { scroll-behavior: auto !important; transition-duration: 0.01ms !important; }
}