qualifier 0.6.1

/* ============================================================
   QUALIFIER — Design System
   Aesthetic: Inspector's logbook. Blueprint precision.
   Cool dark grounds, indigo accent. Light theme is a cool
   pencil-on-paper inversion. Cascade layered:
     reset < base < layout < components.
   ============================================================ */

/* --- Self-hosted fonts ---
   Atkinson Hyperlegible Next, Instrument Sans, JetBrains Mono.
   font-display: optional on the preloaded latin subset weights —
   with <link rel="preload"> the woff2 lands inside the browser's
   ~100ms initial block window, the web font is used, and no swap
   is ever visible. Italic and ext subsets stay on swap (rare on
   the critical path). */

/* Atkinson Hyperlegible Next — body text */
@font-face {
  font-family: "Atkinson Hyperlegible Next";
  font-style: normal;
  font-weight: 400;
  font-display: optional;
  src: url(/fonts/atkinson-regular.woff2) format("woff2");
  unicode-range:
    U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC,
    U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212,
    U+2215, U+FEFF, U+FFFD;
}
@font-face {
  font-family: "Atkinson Hyperlegible Next";
  font-style: normal;
  font-weight: 400;
  font-display: swap;
  src: url(/fonts/atkinson-regular-ext.woff2) format("woff2");
  unicode-range:
    U+0100-02BA, U+02BD-02C5, U+02C7-02CC, U+02CE-02D7, U+02DD-02FF, U+0304,
    U+0308, U+0329, U+1D00-1DBF, U+1E00-1E9F, U+1EF2-1EFF, U+2020, U+20A0-20AB,
    U+20AD-20C0, U+2113, U+2C60-2C7F, U+A720-A7FF;
}
@font-face {
  font-family: "Atkinson Hyperlegible Next";
  font-style: normal;
  font-weight: 600;
  font-display: optional;
  src: url(/fonts/atkinson-regular.woff2) format("woff2");
  unicode-range:
    U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC,
    U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212,
    U+2215, U+FEFF, U+FFFD;
}
@font-face {
  font-family: "Atkinson Hyperlegible Next";
  font-style: normal;
  font-weight: 600;
  font-display: swap;
  src: url(/fonts/atkinson-regular-ext.woff2) format("woff2");
  unicode-range:
    U+0100-02BA, U+02BD-02C5, U+02C7-02CC, U+02CE-02D7, U+02DD-02FF, U+0304,
    U+0308, U+0329, U+1D00-1DBF, U+1E00-1E9F, U+1EF2-1EFF, U+2020, U+20A0-20AB,
    U+20AD-20C0, U+2113, U+2C60-2C7F, U+A720-A7FF;
}
@font-face {
  font-family: "Atkinson Hyperlegible Next";
  font-style: italic;
  font-weight: 400;
  font-display: swap;
  src: url(/fonts/atkinson-italic.woff2) format("woff2");
  unicode-range:
    U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC,
    U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212,
    U+2215, U+FEFF, U+FFFD;
}
@font-face {
  font-family: "Atkinson Hyperlegible Next";
  font-style: italic;
  font-weight: 400;
  font-display: swap;
  src: url(/fonts/atkinson-italic-ext.woff2) format("woff2");
  unicode-range:
    U+0100-02BA, U+02BD-02C5, U+02C7-02CC, U+02CE-02D7, U+02DD-02FF, U+0304,
    U+0308, U+0329, U+1D00-1DBF, U+1E00-1E9F, U+1EF2-1EFF, U+2020, U+20A0-20AB,
    U+20AD-20C0, U+2113, U+2C60-2C7F, U+A720-A7FF;
}

/* Instrument Sans — display/headings (variable weight 400–700) */
@font-face {
  font-family: "Instrument Sans";
  font-style: normal;
  font-weight: 400 700;
  font-stretch: 100%;
  font-display: optional;
  src: url(/fonts/instrument-sans.woff2) format("woff2");
  unicode-range:
    U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC,
    U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212,
    U+2215, U+FEFF, U+FFFD;
}
@font-face {
  font-family: "Instrument Sans";
  font-style: normal;
  font-weight: 400 700;
  font-stretch: 100%;
  font-display: swap;
  src: url(/fonts/instrument-sans-ext.woff2) format("woff2");
  unicode-range:
    U+0100-02BA, U+02BD-02C5, U+02C7-02CC, U+02CE-02D7, U+02DD-02FF, U+0304,
    U+0308, U+0329, U+1D00-1DBF, U+1E00-1E9F, U+1EF2-1EFF, U+2020, U+20A0-20AB,
    U+20AD-20C0, U+2113, U+2C60-2C7F, U+A720-A7FF;
}

/* JetBrains Mono — code (variable weight 400–600) */
@font-face {
  font-family: "JetBrains Mono";
  font-style: normal;
  font-weight: 400 600;
  font-display: optional;
  src: url(/fonts/jetbrains-mono.woff2) format("woff2");
  unicode-range:
    U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC,
    U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212,
    U+2215, U+FEFF, U+FFFD;
}
@font-face {
  font-family: "JetBrains Mono";
  font-style: normal;
  font-weight: 400 600;
  font-display: swap;
  src: url(/fonts/jetbrains-mono-ext.woff2) format("woff2");
  unicode-range:
    U+0100-02BA, U+02BD-02C5, U+02C7-02CC, U+02CE-02D7, U+02DD-02FF, U+0304,
    U+0308, U+0329, U+1D00-1DBF, U+1E00-1E9F, U+1EF2-1EFF, U+2020, U+20A0-20AB,
    U+20AD-20C0, U+2113, U+2C60-2C7F, U+A720-A7FF;
}

@layer reset, base, layout, components;

@layer reset {
  *,
  *::before,
  *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
  }
  img,
  svg {
    display: block;
    max-width: 100%;
  }
  a {
    color: inherit;
    text-decoration: none;
  }
  button {
    background: none;
    border: none;
    color: inherit;
    cursor: pointer;
    font: inherit;
  }
  ul,
  ol {
    list-style: none;
  }
}

@layer base {
  :root {
    /* --- Typography --- */
    --display: "Instrument Sans", "Inter", "Helvetica Neue", sans-serif;
    --body:
      "Atkinson Hyperlegible Next", "Atkinson Hyperlegible", system-ui,
      sans-serif;
    --mono: "JetBrains Mono", "SF Mono", "Consolas", monospace;

    /* --- Spacing --- */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2.5rem;
    --space-2xl: 4rem;

    /* --- Layout primitives --- */
    --max-w: 56rem; /* ~896px — single content width; matches family rhythm */
    --nav-h: 3.5rem; /* ~56px */

    /* --- Dark theme (canonical) --- */
    /* Surfaces — the lift ramp */
    --void: #0c0e11;
    --slab: #141720;
    --plate: #1b1f2a;
    --ridge: #252a38;

    /* Text — graphite to chalk */
    --steel: #3a4158;
    --flint: #6b7394;
    --ash: #9ba3bf;
    --chalk: #d0d5e3;
    --white: #eef0f6;

    /* Accent — the inspector's mark (indigo) */
    --accent: #818cf8;
    --accent-dim: #818cf815;
    --accent-mid: #818cf840;

    /* Signal — verdict colors */
    --pass: #34d399;
    --pass-dim: #34d39920;
    --warn: #fbbf24;
    --warn-dim: #fbbf2420;
    --fail: #f87171;
    --fail-dim: #f8717120;
    --info: #60a5fa;
    --info-dim: #60a5fa20;

    /* Grid paper */
    --grid-line: #ffffff06;
    --grid-line-major: #ffffff0a;

    /* Prism token colors — dark theme */
    --syn-property: #c4b5fd;
    --syn-string: #6ee7b7;
    --syn-number: #fcd34d;
    --syn-keyword: #f0abfc;
    --syn-function: #93c5fd;
  }

  /* --- Light theme — cool pencil-on-paper inversion ---
     Cool off-white grounds (never warm beige), graphite text, an
     indigo-600 accent that meets WCAG AA on the lifted grounds. The
     surface ramp stays cool-cast so the grid paper still reads as
     blueprint paper, not a kraft sheet. */
  [data-theme="light"] {
    /* Surfaces invert: lightest at the page ground, darker on lifts */
    --void: #f5f7fa;
    --slab: #eaeef4;
    --plate: #dde2eb;
    --ridge: #c8cdd9;

    /* Text inverts: --white is now max-contrast graphite at the top.
       --steel is the lightest hint tier on the light ground; we hold it
       a touch darker than --ridge so the ramp doesn't collapse and so
       footer / code comments stay readable (≈3.4:1 on --void — same
       low-but-legible "hint" register as on the dark theme). */
    --steel: #9098ad;
    --flint: #6b7394;
    --ash: #4a5168;
    --chalk: #1a1d2a;
    --white: #0a0c14;

    /* Accent — indigo-600 for AA contrast on light grounds */
    --accent: #4f46e5;
    --accent-dim: #4f46e515;
    --accent-mid: #4f46e540;

    /* Signal — slightly desaturated for light bg */
    --pass: #059669;
    --pass-dim: #05966920;
    --warn: #d97706;
    --warn-dim: #d9770620;
    --fail: #dc2626;
    --fail-dim: #dc262620;
    --info: #2563eb;
    --info-dim: #2563eb20;

    /* Grid lines — much fainter on light */
    --grid-line: #00000008;
    --grid-line-major: #0000000d;

    /* Prism tokens — darker variants for AA contrast on light bg */
    --syn-property: #6d28d9; /* violet-700 */
    --syn-string: #047857; /* emerald-700 */
    --syn-number: #b45309; /* amber-700 */
    --syn-keyword: #a21caf; /* fuchsia-700 */
    --syn-function: #1d4ed8; /* blue-700 */
  }

  html {
    font-size: 16px;
    line-height: 1.6;
    color: var(--chalk);
    background: var(--void);
    scroll-behavior: smooth;
    scroll-padding-top: var(--nav-h);
  }

  /* Font load coordination. The inline <head> script adds
     `.fonts-loading` to <html> and removes it once every preloaded
     weight has resolved (or a 1500ms timeout fires). Hiding the body
     during that window collapses multi-stage FOUT into a single
     render commit. The page still has its bg color from <html>, so
     it doesn't flash white. */
  html.fonts-loading body {
    visibility: hidden;
  }

  body {
    font-family: var(--body);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
  }

  ::selection {
    background: var(--accent);
    color: var(--void);
  }

  /* --- Typography --- */
  h1 {
    font-family: var(--display);
    font-weight: 700;
    font-size: 1.5rem;
    line-height: 1.2;
    color: var(--white);
    margin: 2.5rem 0 1rem;
    letter-spacing: -0.01em;
  }
  h2 {
    font-family: var(--display);
    font-weight: 600;
    font-size: 1.15rem;
    line-height: 1.3;
    color: var(--white);
    margin: 2.5rem 0 0.6rem;
    letter-spacing: -0.005em;
    border-bottom: 1px solid var(--ridge);
    padding-bottom: 0.4rem;
  }
  h3 {
    font-family: var(--display);
    font-weight: 600;
    font-size: 0.82rem;
    line-height: 1.3;
    color: var(--ash);
    margin: 1.5rem 0 0.4rem;
    text-transform: uppercase;
    letter-spacing: 0.06em;
  }
  h4 {
    font-family: var(--mono);
    font-weight: 600;
    font-size: 0.8rem;
    line-height: 1.3;
    color: var(--flint);
    text-transform: uppercase;
    letter-spacing: 0.04em;
    margin: 1.25rem 0 0.4rem;
  }

  p {
    margin: 0.75rem 0;
  }
  a {
    color: var(--accent);
    text-decoration: none;
    transition: color 0.15s;
  }
  a:hover {
    color: var(--white);
    text-decoration: underline;
    text-decoration-thickness: 1px;
    text-underline-offset: 2px;
  }

  ul,
  ol {
    margin: 0.75rem 0 0.75rem 1.5rem;
  }
  ul {
    list-style: disc;
  }
  ol {
    list-style: decimal;
  }
  li {
    margin: 0.25rem 0;
  }
  strong {
    font-weight: 600;
    color: var(--white);
  }

  /* --- Heading anchors --- */
  h1 > a.header-anchor,
  h2 > a.header-anchor,
  h3 > a.header-anchor,
  h4 > a.header-anchor {
    color: inherit;
    text-decoration: none;
  }
  h1 > a.header-anchor:hover,
  h2 > a.header-anchor:hover,
  h3 > a.header-anchor:hover,
  h4 > a.header-anchor:hover {
    text-decoration: underline;
    text-decoration-color: var(--accent);
    text-decoration-thickness: 2px;
    text-underline-offset: 3px;
  }

  /* --- Code --- */
  code {
    font-family: var(--mono);
    font-size: 0.84em;
    background: var(--plate);
    padding: 0.15em 0.4em;
    border-radius: 3px;
    color: var(--chalk);
    border: 1px solid var(--ridge);
  }
  pre {
    background: var(--slab);
    border: 1px solid var(--ridge);
    border-left: 3px solid var(--accent-mid);
    padding: 1rem 1.25rem;
    overflow-x: auto;
    margin: 1rem 0;
    line-height: 1.55;
    border-radius: 2px;
  }
  pre code {
    background: none;
    padding: 0;
    font-size: 0.82rem;
    border: none;
    border-radius: 0;
  }

  /* --- Prism syntax tokens --- */
  .token.property {
    color: var(--syn-property);
  }
  .token.string,
  .token.url {
    color: var(--syn-string);
  }
  .token.number {
    color: var(--syn-number);
  }
  .token.keyword,
  .token.selector {
    color: var(--syn-keyword);
  }
  .token.function,
  .token.class-name {
    color: var(--syn-function);
  }
  .token.operator {
    color: var(--ash);
  }
  .token.punctuation {
    color: var(--flint);
  }
  .token.comment {
    color: var(--steel);
    font-style: italic;
  }
  .token.namespace {
    opacity: 0.7;
  }

  /* --- Tables --- */
  table {
    border-collapse: collapse;
    width: 100%;
    margin: 1rem 0;
    font-size: 0.92rem;
  }
  th,
  td {
    text-align: left;
    padding: 0.5rem 0.75rem;
    border-bottom: 1px solid var(--ridge);
  }
  th {
    font-family: var(--mono);
    font-weight: 600;
    font-size: 0.72rem;
    color: var(--flint);
    text-transform: uppercase;
    letter-spacing: 0.08em;
  }
}

@layer layout {
  body {
    /* Push content below the fixed nav. */
    padding: var(--nav-h) var(--space-lg) 0;
  }

  main {
    max-width: var(--max-w);
    margin: 0 auto;
    padding: var(--space-lg) 0 var(--space-2xl);
  }

  /* --- Prose container ---
     Long-form pages constrain prose-flow children to ~62ch for
     comfortable reading. Wide elements (code blocks, tables,
     code-compare, figures, headings) stay at the body's full width
     so the spec's wide tables and anchored heading structure render
     unchanged. */
  /* Long-form pages share one content width with the rest of the site
     (--max-w on main). The .prose class is kept as a hook for any
     future prose-specific overrides but applies no layout constraint
     of its own. */

  @media (max-width: 600px) {
    body {
      padding-left: 1.25rem;
      padding-right: 1.25rem;
    }
    main {
      padding: var(--space-md) 0 var(--space-2xl);
    }
  }
}

@layer components {
  /* --- Navigation --- */
  .site-nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 100;
    height: var(--nav-h);
    background: var(--void);
    border-bottom: 1px solid var(--ridge);
    display: flex;
    align-items: center;
    /* Nav is chrome — mono throughout, regardless of body type. */
    font-family: var(--mono);
    font-size: 0.78rem;
  }
  .site-nav-inner {
    /* +2*space-lg matches the body's outer side padding so nav and main
       share content edges on viewports wider than the container. */
    max-width: calc(var(--max-w) + 2 * var(--space-lg));
    margin: 0 auto;
    width: 100%;
    padding: 0 var(--space-lg);
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-md);
    height: 100%;
  }
  .nav-logo {
    font-family: var(--display);
    font-weight: 700;
    font-size: 0.9rem;
    text-decoration: none;
    color: var(--white);
    letter-spacing: -0.02em;
    display: flex;
    align-items: center;
    gap: 0.5rem;
  }
  .nav-logo::before {
    content: "";
    display: inline-block;
    width: 8px;
    height: 8px;
    background: var(--accent);
    border-radius: 1px;
    flex-shrink: 0;
  }
  .nav-right {
    display: flex;
    align-items: center;
    gap: 2px;
  }
  .nav-links {
    display: flex;
    align-items: center;
    gap: 1.25rem;
  }
  .nav-links a {
    font-family: var(--mono);
    font-weight: 500;
    text-decoration: none;
    font-size: 0.75rem;
    color: var(--flint);
    letter-spacing: 0.02em;
    padding: 6px 0;
    transition: color 0.15s;
  }
  .nav-links a:hover {
    color: var(--white);
    text-decoration: none;
  }
  .nav-links a[aria-current] {
    color: var(--accent);
  }
  .nav-github {
    opacity: 0.5;
  }
  .nav-github:hover {
    opacity: 1;
  }

  /* --- Theme toggle --- */
  .theme-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 6px 8px;
    margin-left: var(--space-sm);
    color: var(--flint);
    line-height: 1;
    transition: color 0.15s;
  }
  .theme-toggle:hover {
    color: var(--accent);
  }
  .theme-toggle svg {
    display: none;
    width: 14px;
    height: 14px;
  }
  /* Default: system pref shows the desktop (monitor) icon */
  [data-theme-pref="system"] .theme-toggle .icon-system-desktop {
    display: block;
  }
  /* Touch / coarse-pointer devices: show the phone icon for system pref */
  @media (hover: none) and (pointer: coarse) {
    [data-theme-pref="system"] .theme-toggle .icon-system-desktop {
      display: none;
    }
    [data-theme-pref="system"] .theme-toggle .icon-system-mobile {
      display: block;
    }
  }
  [data-theme-pref="dark"] .theme-toggle .icon-dark {
    display: block;
  }
  [data-theme-pref="light"] .theme-toggle .icon-light {
    display: block;
  }

  /* --- Mobile menu --- */
  .nav-menu-btn {
    display: none;
    font-size: 18px;
    line-height: 1;
    padding: 4px 6px;
    color: var(--flint);
  }
  .nav-menu-btn:hover {
    color: var(--white);
  }
  @media (max-width: 700px) {
    .nav-links a:not(.nav-github):not(.theme-toggle) {
      display: none;
    }
    .nav-menu-btn {
      display: block;
    }
    [data-menu-open] .nav-links {
      position: absolute;
      top: var(--nav-h);
      left: 0;
      right: 0;
      flex-direction: column;
      align-items: stretch;
      background: var(--void);
      border-bottom: 1px solid var(--ridge);
      padding: 0.5rem var(--space-lg) 0.75rem;
      gap: 0;
    }
    [data-menu-open] .nav-links a:not(.nav-github):not(.theme-toggle) {
      display: block;
      padding: 0.5rem 0;
    }
  }
  @media (max-width: 600px) {
    .site-nav-inner {
      padding: 0 1.25rem;
    }
  }

  /* --- Divider --- */
  .divider {
    height: 1px;
    background: var(--ridge);
    margin: 0;
    position: relative;
  }
  .divider::after {
    content: "";
    position: absolute;
    left: 0;
    top: 0;
    width: 48px;
    height: 1px;
    background: var(--accent);
  }

  /* --- Footer ---
     Family standard: a single centered paragraph, mono, --steel.
     Copyright + GitHub + docs.rs + crates.io separated by middots. */
  .site-footer {
    margin-top: var(--space-2xl);
    padding: var(--space-lg) 0;
    border-top: 1px solid var(--ridge);
    font-family: var(--mono);
    font-size: 0.72rem;
    color: var(--steel);
    text-align: center;
    letter-spacing: 0.04em;
  }
  .site-footer a {
    color: var(--steel);
  }
  .site-footer a:hover {
    color: var(--accent);
  }

  /* --- Hero --- */
  .hero {
    padding: 4rem 0 3rem;
    border-bottom: none;
    margin-bottom: 0;
    display: flex;
    align-items: flex-start;
    gap: 3rem;
  }
  .hero-content {
    flex: 1;
    min-width: 0;
  }
  .hero h1 {
    font-size: clamp(1.8rem, 5vw, 2.6rem);
    margin: 0 0 0.75rem;
    line-height: 1.2;
    letter-spacing: -0.02em;
    color: var(--white);
  }
  .hero h1 .hero-mark {
    color: var(--accent);
  }
  .hero .tagline {
    font-family: var(--body);
    font-size: 1.05rem;
    color: var(--ash);
    margin: 0 0 1.75rem;
    max-width: 44rem;
    line-height: 1.6;
  }
  .hero .tagline strong {
    color: var(--white);
    font-weight: 600;
  }
  .hero-install {
    font-family: var(--mono);
    font-size: 0.85rem;
    background: var(--slab);
    border: 1px solid var(--ridge);
    border-left: 3px solid var(--accent-mid);
    padding: 0.6rem 1rem;
    display: inline-block;
    border-radius: 2px;
  }
  .hero-install .prompt {
    color: var(--flint);
    user-select: none;
  }
  .try-it-btn {
    font-family: var(--mono);
    font-size: 0.78rem;
    font-weight: 500;
    letter-spacing: 0.06em;
    text-transform: uppercase;
    color: var(--accent);
    background: transparent;
    border: 1px solid var(--accent);
    padding: 0.6rem 1.25rem;
    margin-left: var(--space-md);
    cursor: pointer;
    transition:
      background-color 0.15s,
      color 0.15s;
    vertical-align: middle;
    border-radius: 2px;
  }
  .try-it-btn:hover {
    background: var(--accent);
    color: var(--void);
  }
  .try-it-btn:disabled {
    opacity: 0.3;
    cursor: default;
  }
  .hero + .divider {
    margin-bottom: 2rem;
  }

  /* --- Stacked code comparison ---
     Two records, each at full content width, stacked vertically with a
     small uppercase label above each. Side-by-side at our measure
     forced narrow panes that wrapped or scrolled pretty-printed JSON;
     stacking trades vertical space for legibility. */
  .code-compare {
    margin: 1.25rem 0;
    display: flex;
    flex-direction: column;
    gap: 1rem;
  }
  .code-compare .cc-section {
    display: flex;
    flex-direction: column;
  }
  .code-compare .cc-label {
    font-family: var(--mono);
    font-size: 0.72rem;
    color: var(--flint);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    padding: 0.25rem 0;
    margin-bottom: 0.4rem;
    border-bottom: 1px solid var(--ridge);
    user-select: none;
  }
  .code-compare .cc-pane > pre {
    margin: 0;
  }
  /* Distinguish the record body from the envelope: heavier weight and
     slightly brighter text. Stays inline so there's no layout disruption. */
  .record-body .token {
    font-weight: 600;
  }
  .record-body .token.property {
    color: var(--white);
  }

  /* --- Concept cards --- */
  .concepts {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(17rem, 1fr));
    gap: 1px;
    margin: 1.5rem 0;
    background: var(--ridge);
  }
  .concept-card {
    background: var(--slab);
    padding: 1.25rem 1.5rem;
  }
  .concept-card h3 {
    margin: 0 0 0.5rem;
    font-size: 0.78rem;
    color: var(--accent);
    letter-spacing: 0.06em;
  }
  .concept-card p {
    margin: 0;
    font-size: 0.9rem;
    color: var(--ash);
    line-height: 1.55;
  }

  /* --- Score bar (inline) --- */
  .score-bar {
    font-family: var(--mono);
    font-size: 0.82rem;
    letter-spacing: 0.02em;
  }
  .score-bar .filled {
    color: var(--pass);
  }
  .score-bar .empty {
    color: var(--ridge);
  }
  .score-bar .negative {
    color: var(--fail);
  }

  /* --- Propagation diagram --- */
  .propagation-figure {
    background: var(--slab);
    border: 1px solid var(--ridge);
    padding: 1.5rem 1.5rem 1rem;
    margin: 1.25rem 0;
    overflow-x: auto;
    border-radius: 2px;
  }
  .propagation-svg {
    display: block;
    width: 100%;
    max-width: 700px;
    height: auto;
    margin: 0 auto;
  }

  /* --- Subtitle --- */
  .subtitle {
    font-family: var(--body);
    font-size: 1rem;
    color: var(--ash);
    margin-bottom: 2rem;
    line-height: 1.6;
  }

  /* --- Blueprint illustrations --- */
  .topo {
    display: block;
    pointer-events: none;
  }
  .topo-hero {
    width: clamp(200px, 35%, 340px);
    height: auto;
    flex-shrink: 0;
  }
  .topo-wide {
    width: 100%;
    height: auto;
    margin: 1.5rem 0;
  }

  /* --- Page title --- */
  .page-title {
    margin-top: 2rem;
  }

  /* --- Kind badge --- */
  .kind-badge {
    font-family: var(--mono);
    font-size: 0.68rem;
    font-weight: 600;
    letter-spacing: 0.04em;
    text-transform: uppercase;
    padding: 0.15rem 0.5rem;
    display: inline-block;
    border-radius: 2px;
  }
  .kind-badge.positive {
    background: var(--pass-dim);
    color: var(--pass);
    border: 1px solid var(--pass-dim);
  }
  .kind-badge.negative {
    background: var(--fail-dim);
    color: var(--fail);
    border: 1px solid var(--fail-dim);
  }
  .kind-badge.neutral {
    background: var(--accent-dim);
    color: var(--accent);
    border: 1px solid var(--accent-mid);
  }

  /* --- Spec content --- */
  .spec-content h2 {
    margin-top: 3rem;
  }
  .spec-content h3 {
    margin-top: 2rem;
  }

  /* --- Responsive --- */
  @media (max-width: 640px) {
    html {
      font-size: 15px;
    }
    .hero {
      flex-direction: column;
      padding: 2.5rem 0 2rem;
    }
    .topo-hero {
      width: 80%;
      max-width: 280px;
    }
    .concepts {
      grid-template-columns: 1fr;
    }
    .try-it-btn {
      margin-left: 0;
      margin-top: var(--space-sm);
    }
  }
}