/* VPN Learning: product layer on top of family.css.

   Identity: a field guide. A numbered route line runs through the reading
   path, articles read like chapters with a contents rail and a hairline of
   reading progress, and legal and policy notices are set apart by a double
   rule (shape, not colour alone). One accent: petrol ink, used for action,
   focus, the current section, step numbers and progress only.

   Breakpoints (media queries cannot read custom properties):
     600px   tables stop stacking; two-column compare blocks
     769px   navigation expands (family); 769 to 1099px hides the brand
             subtitle so the header stays on one row
     834px   two-column topic grid
     1024px  intro beside the policy panel; article contents rail
   Review widths: 390, 834 and 1440 CSS pixels; 200% zoom on 1440 behaves
   as 720 and uses the single-column layout.

   Motion: this layer animates only transform and opacity, 120 to 200ms;
   reduced motion removes it (family.css).                                   */

:root {
  --accent: #1d5a63;
  --accent-hover: #134249;
  --accent-soft: #dce9ea;
  --on-accent: #fbf9f5;
  --focus: #1d5a63;
  --caution: #8a4a00;
  --legal-edge: #1c1b19;
}

[data-theme="dark"] {
  --accent: #8dcdd4;
  --accent-hover: #b6e1e5;
  --accent-soft: #16292c;
  --on-accent: #0b1a1c;
  --focus: #8dcdd4;
  --caution: #f0b66a;
  --legal-edge: #ece7de;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --accent: #8dcdd4;
    --accent-hover: #b6e1e5;
    --accent-soft: #16292c;
    --on-accent: #0b1a1c;
    --focus: #8dcdd4;
    --caution: #f0b66a;
    --legal-edge: #ece7de;
  }
}

/* ---- Progressive enhancement and header --------------------------------- */

html:not(.js) .js-only {
  display: none;
}

.js .glossary-filter.js-only {
  display: block;
}

.js .checklist-reset.js-only {
  display: inline-flex;
}

.js .reading-progress.js-only {
  display: block;
}

@media (min-width: 769px) and (max-width: 1099px) {
  .brand-sub {
    display: none;
  }
}

/* ---- Small shared parts --------------------------------------------------- */

.arrow {
  display: inline-block;
  transition: transform var(--dur-fast) var(--ease-out);
}

a:hover .arrow {
  transform: translateX(2px);
}

a:hover .arrow-back {
  transform: translateX(-2px);
}

.crumbs ol {
  display: flex;
  flex-wrap: wrap;
  gap: 0 var(--space-2);
  margin: 0 0 var(--space-3);
  padding: 0;
  list-style: none;
  font-size: var(--text-sm);
}

.crumbs li {
  margin: 0;
  color: var(--text-muted);
}

.crumbs li + li::before {
  content: "/";
  margin-right: var(--space-2);
  color: var(--border-strong);
}

.crumbs a {
  display: inline-flex;
  align-items: center;
  min-height: var(--target);
  color: var(--text-muted);
}

.crumbs a:hover {
  color: var(--text);
}

.intro-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  margin: var(--space-4) 0 0;
}

.mark-list {
  padding: 0;
  list-style: none;
}

.mark-list li {
  position: relative;
  padding-left: var(--space-5);
}

.mark-list li::before {
  position: absolute;
  left: 0;
  top: 0;
  font-family: var(--font-mono);
  font-weight: 700;
}

.mark-yes li::before {
  content: "+";
  color: var(--success);
}

.mark-no li::before {
  content: "\2212";
  color: var(--danger);
}

/* ---- Home ------------------------------------------------------------------ */

.vl-intro {
  padding: var(--space-7) 0 var(--space-6);
  border-bottom: 1px solid var(--border);
}

.vl-intro-grid {
  display: grid;
  gap: var(--space-6);
}

.vl-intro h1 {
  max-width: 13em;
}

.principles {
  display: grid;
  gap: var(--space-2);
  margin: var(--space-5) 0 0;
  padding: var(--space-4) 0 0;
  border-top: 1px solid var(--border);
  list-style: none;
  color: var(--text-muted);
  font-size: var(--text-sm);
}

.principles li {
  position: relative;
  margin: 0;
  padding-left: var(--space-5);
}

.principles li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.55em;
  width: 0.625rem;
  height: 0.625rem;
  border: 2px solid var(--accent);
  border-radius: 50%;
}

@media (min-width: 1024px) {
  .vl-intro-grid {
    grid-template-columns: minmax(0, 7fr) minmax(0, 5fr);
    gap: var(--space-8);
    align-items: start;
  }
}

/* Legal and policy notices: a double rule, the one place it is used. */
.policy-panel {
  padding: var(--space-5);
  border: 1px solid var(--border);
  border-top: 4px double var(--legal-edge);
  border-radius: 0 0 var(--radius-lg) var(--radius-lg);
  background: var(--surface-raised);
  box-shadow: var(--shadow-1);
}

.policy-tone {
  margin: 0 0 var(--space-2);
  color: var(--text-muted);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.policy-title {
  margin-bottom: var(--space-3);
  font-size: var(--text-lg);
}

.policy-rules {
  padding: 0;
  list-style: none;
}

.policy-rules li {
  margin: 0;
  padding: var(--space-3) 0;
  border-top: 1px solid var(--border);
}

.policy-rules strong {
  display: block;
}

.policy-foot {
  margin: 0;
  color: var(--text-muted);
  font-size: var(--text-sm);
}

.policy-foot a {
  display: inline-flex;
  align-items: center;
  min-height: var(--target);
}

/* The reading path: a route line through numbered steps. */
.path-intro {
  max-width: 60ch;
}

.path-list {
  position: relative;
  margin: 0;
  padding: 0;
  list-style: none;
}

.path-list::before {
  content: "";
  position: absolute;
  left: 1.25rem;
  top: 1.5rem;
  bottom: 1.5rem;
  border-left: 2px dotted var(--border-strong);
}

.path-row {
  position: relative;
  display: grid;
  grid-template-columns: 2.5rem minmax(0, 1fr);
  gap: var(--space-4);
  margin: 0;
  padding: var(--space-4) 0;
}

.path-step {
  position: relative;
  display: grid;
  place-items: center;
  width: 2.5rem;
  height: 2.5rem;
  border: 2px solid var(--accent);
  border-radius: 50%;
  background: var(--bg);
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  font-weight: 700;
}

.path-meta {
  margin: 0 0 var(--space-1);
  color: var(--text-muted);
}

.path-title {
  margin: 0 0 var(--space-1);
  font-family: var(--font-display);
  font-size: var(--text-lg);
  font-weight: 600;
}

.path-title a {
  display: inline-flex;
  align-items: center;
  min-height: var(--target);
  color: var(--text);
  text-decoration: none;
}

.path-title a:hover {
  color: var(--accent);
  text-decoration: underline;
}

.path-summary {
  max-width: 64ch;
  margin: 0;
  color: var(--text-muted);
}

.topic-grid {
  display: grid;
  gap: 0 var(--space-6);
  margin: 0;
  padding: 0;
  list-style: none;
}

.topic-grid li {
  margin: 0;
}

.topic-link {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: var(--space-1) var(--space-4);
  min-height: var(--target);
  padding: var(--space-4) var(--space-2);
  border-bottom: 1px solid var(--border);
  color: var(--text);
  text-decoration: none;
}

.topic-link:hover {
  background: var(--surface-raised);
  color: var(--text);
}

.topic-link:hover .topic-label {
  text-decoration: underline;
}

.topic-label {
  font-weight: 650;
}

.topic-desc {
  grid-column: 1;
  color: var(--text-muted);
  font-size: var(--text-sm);
}

.topic-count {
  grid-column: 2;
  grid-row: 1;
  color: var(--accent);
  font-weight: 600;
}

@media (min-width: 834px) {
  .topic-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

.term-teaser,
.term-list {
  display: grid;
  gap: var(--space-4) var(--space-6);
  margin: 0;
}

.term-teaser div,
.term-list div {
  padding-top: var(--space-3);
  border-top: 1px solid var(--border);
}

.term-teaser dt a,
.term-list dt a {
  display: inline-flex;
  align-items: center;
  min-height: var(--target);
  font-weight: 650;
}

.term-teaser dd,
.term-list dd {
  margin: 0;
  color: var(--text-muted);
  font-size: var(--text-sm);
}

@media (min-width: 834px) {
  .term-teaser {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

/* ---- Learn ------------------------------------------------------------------ */

.topic-jump {
  margin-top: var(--space-5);
}

.learn-groups {
  padding-top: var(--space-6);
}

.topic-block {
  margin-bottom: var(--space-7);
}

/* ---- Article ---------------------------------------------------------------- */

.reading-progress {
  position: sticky;
  top: var(--header-height);
  z-index: 40;
  height: 3px;
  margin-bottom: -3px;
  pointer-events: none;
}

.reading-progress span {
  display: block;
  height: 100%;
  background: var(--accent);
  transform: scaleX(0);
  transform-origin: left center;
  transition: transform var(--dur-fast) linear;
}

.lesson-head {
  padding: var(--space-5) 0 var(--space-5);
  border-bottom: 1px solid var(--border);
}

.lesson-head h1 {
  max-width: 20em;
  margin-bottom: var(--space-3);
  font-size: clamp(1.875rem, 1.35rem + 1.9vw, 2.75rem);
}

.lesson-meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2) var(--space-6);
  margin: var(--space-4) 0 0;
}

.lesson-meta dt {
  color: var(--text-muted);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.lesson-meta dd {
  margin: 0;
}

.lesson-grid {
  display: grid;
  gap: var(--space-5);
  padding-top: var(--space-6);
}

.toc {
  padding: var(--space-3) 0 var(--space-3) var(--space-4);
  border-left: 2px solid var(--border);
}

.toc-title {
  margin: 0 0 var(--space-1);
  color: var(--text-muted);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.toc ol,
.about-contents ol {
  margin: 0;
  padding: 0;
  list-style: none;
}

.toc li + li,
.about-contents li + li {
  margin-top: 0;
}

.toc a,
.about-contents a {
  display: flex;
  align-items: center;
  min-height: var(--target);
  padding: var(--space-1) 0;
  color: var(--text-muted);
  font-size: var(--text-sm);
  line-height: 1.35;
  text-decoration: none;
}

.toc a:hover,
.about-contents a:hover {
  color: var(--text);
  text-decoration: underline;
}

/* The current section lights its segment of the contents rule. */
.toc a[aria-current="location"] {
  margin-left: calc(-1 * var(--space-4) - 2px);
  padding-left: var(--space-4);
  border-left: 2px solid var(--accent);
  color: var(--accent);
  font-weight: 600;
}

.toc-status {
  margin: var(--space-2) 0 0;
  color: var(--text-muted);
}

@media (min-width: 1024px) {
  .lesson-grid {
    grid-template-columns: 15rem minmax(0, 1fr);
    gap: var(--space-8);
    align-items: start;
  }

  .toc,
  .about-contents {
    position: sticky;
    top: calc(var(--header-height) + var(--space-5));
    max-height: calc(100vh - var(--header-height) - var(--space-7));
    overflow-y: auto;
  }
}

.lesson-body {
  min-width: 0;
  max-width: 72ch;
}

.key-points {
  margin-bottom: var(--space-6);
  padding: var(--space-4) var(--space-5);
  border-left: 3px solid var(--accent);
  background: var(--surface);
}

.key-points-title {
  margin: 0 0 var(--space-2);
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.key-points ul {
  margin: 0;
}

.prose {
  font-size: var(--text-md);
  line-height: 1.7;
}

.lesson-section,
.about-block {
  margin-bottom: var(--space-7);
}

.lesson-section h2,
.about-block h2 {
  padding-bottom: var(--space-2);
  border-bottom: 2px solid var(--rule);
  font-size: var(--text-xl);
}

.lesson-section.is-scope {
  padding: var(--space-5);
  border: 1px solid var(--border);
  border-top: 4px double var(--legal-edge);
  background: var(--surface-raised);
}

.lesson-section.is-scope h2 {
  border-bottom: 0;
  font-size: var(--text-lg);
}

.lesson-body > .policy-panel {
  margin: var(--space-6) 0;
}

.lesson-extra {
  margin-top: var(--space-6);
}

.lesson-extra h2 {
  font-size: var(--text-lg);
}

.related-list {
  padding: 0;
  list-style: none;
}

.related-list a {
  display: inline-flex;
  align-items: center;
  min-height: var(--target);
}

.pager {
  display: grid;
  gap: var(--space-3);
  margin-top: var(--space-7);
  padding-top: var(--space-4);
  border-top: 2px solid var(--rule);
}

@media (min-width: 600px) {
  .pager {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

.pager-link {
  display: grid;
  gap: var(--space-1);
  min-height: var(--target);
  padding: var(--space-3) var(--space-4);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  color: var(--text);
  text-decoration: none;
}

.pager-link:hover {
  border-color: var(--text);
  background: var(--surface-raised);
  color: var(--text);
}

.pager-next {
  grid-column: -2;
  text-align: right;
}

.pager-label {
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.pager-title {
  font-weight: 600;
}

/* ---- Blocks (family/blockkit.py) ------------------------------------------- */

.block-steps {
  padding: 0;
  list-style: none;
  counter-reset: step;
}

.block-step {
  position: relative;
  padding-left: var(--space-7);
  counter-increment: step;
}

.block-step::before {
  content: counter(step);
  position: absolute;
  left: 0;
  top: 0.1rem;
  display: grid;
  place-items: center;
  width: 2rem;
  height: 2rem;
  border-radius: 50%;
  background: var(--accent);
  color: var(--on-accent);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  font-weight: 700;
}

.block-step p {
  margin-bottom: var(--space-1);
}

.callout {
  margin: var(--space-5) 0;
  padding: var(--space-4) var(--space-5);
  border: 1px solid var(--border);
  border-left: 4px solid var(--text-muted);
  border-radius: 0 var(--radius) var(--radius) 0;
  background: var(--surface-raised);
  font-size: var(--text-base);
}

.callout p {
  margin-bottom: var(--space-2);
}

.callout p:last-child {
  margin-bottom: 0;
}

.callout-caution {
  border-left-color: var(--caution);
}

.callout-legal {
  border-left: 6px double var(--legal-edge);
}

.callout-tone {
  color: var(--text-muted);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.compare {
  display: grid;
  gap: var(--space-4) var(--space-6);
}

@media (min-width: 600px) {
  .compare {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

.compare-col {
  padding-top: var(--space-3);
  border-top: 2px solid var(--rule);
}

.block-defs {
  font-size: var(--text-base);
}

/* Checklists: real checkboxes with 44px labels. */
.checklist {
  margin: var(--space-5) 0;
  padding: var(--space-4) var(--space-5);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-lg);
  background: var(--surface-raised);
  font-size: var(--text-base);
}

.checklist-head {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--space-2) var(--space-4);
}

.checklist-title {
  margin: 0 0 var(--space-2);
}

.checklist-progress {
  margin: 0;
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 600;
}

.checklist-items {
  margin: 0 0 var(--space-2);
  padding: 0;
  list-style: none;
}

.checklist-items li {
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  margin: 0;
  border-top: 1px solid var(--border);
}

.checklist-items input {
  flex: none;
  width: 1.25rem;
  height: 1.25rem;
  margin: 0.75rem 0 0;
  accent-color: var(--accent);
}

.checklist-items label {
  flex: 1;
  min-height: var(--target);
  padding: var(--space-2) 0;
  cursor: pointer;
}

.checklist-items input:checked + label {
  color: var(--text-muted);
}

/* Tables stack into labelled cards on narrow screens. */
table.stack caption {
  font-size: var(--text-sm);
}

table.stack td,
table.stack th {
  font-size: var(--text-sm);
}

@media (max-width: 599px) {
  table.stack thead {
    position: absolute;
    width: 1px;
    height: 1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
  }

  table.stack,
  table.stack tbody,
  table.stack tr,
  table.stack th,
  table.stack td {
    display: block;
    width: 100%;
  }

  table.stack tr {
    padding: var(--space-3) 0;
    border-bottom: 1px solid var(--border);
  }

  table.stack th[scope="row"] {
    padding: 0 0 var(--space-1);
    border: 0;
    color: var(--text);
    font-size: var(--text-base);
  }

  table.stack td {
    padding: var(--space-1) 0;
    border: 0;
  }

  table.stack td::before {
    content: attr(data-label);
    display: block;
    color: var(--text-muted);
    font-family: var(--font-mono);
    font-size: var(--text-xs);
    font-weight: 600;
    letter-spacing: 0.04em;
    text-transform: uppercase;
  }
}

/* ---- Glossary --------------------------------------------------------------- */

.glossary-filter {
  max-width: 32rem;
  margin-bottom: var(--space-5);
}

.glossary-list {
  display: grid;
  gap: 0 var(--space-6);
  margin: 0;
}

.term {
  padding: var(--space-4) 0;
  border-bottom: 1px solid var(--border);
}

.term:target {
  background: var(--accent-soft);
  box-shadow: -0.75rem 0 0 var(--accent-soft), 0.75rem 0 0 var(--accent-soft);
}

.term dt {
  font-size: var(--text-md);
  font-weight: 650;
}

.term dfn {
  font-style: normal;
}

.term dd {
  margin: var(--space-1) 0 0;
  color: var(--text-muted);
}

.term-see {
  margin: var(--space-2) 0 0;
  font-size: var(--text-sm);
}

.term-see a {
  display: inline-flex;
  align-items: center;
  min-height: var(--target);
}

@media (min-width: 834px) {
  .glossary-list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

/* ---- About ------------------------------------------------------------------ */

.about-layout {
  display: grid;
  gap: var(--space-6);
  padding-top: var(--space-6);
}

.about-contents {
  padding-left: var(--space-4);
  border-left: 2px solid var(--border);
}

@media (min-width: 1024px) {
  .about-layout {
    grid-template-columns: 14rem minmax(0, 1fr);
    gap: var(--space-8);
    align-items: start;
  }
}

.about-layout .prose {
  max-width: 70ch;
}

/* ---- Preferences --------------------------------------------------------- */

/* Reduced motion: family.css collapses the bar's transition, so it follows
   scrolling without easing; it still moves only when the reader scrolls. */

@media (forced-colors: active) {
  .reading-progress span,
  .block-step::before {
    forced-color-adjust: none;
    background: CanvasText;
    color: Canvas;
  }

  .policy-panel,
  .callout-legal,
  .lesson-section.is-scope {
    border-color: CanvasText;
  }
}

@media print {
  .toc,
  .about-contents,
  .reading-progress,
  .pager,
  .glossary-filter,
  .checklist-reset {
    display: none !important;
  }

  .lesson-grid {
    display: block;
  }
}