/* ============================================================================
   Formalizing Materials R&D — modular reference site
   Design system v2 — "editorial scientific monograph meets premium docs".
   OKLCH luminance-first palette (hex fallbacks), IBM Plex superfamily,
   constrained measure, borders+tints over shadows, tuned dark mode.
   Framework-free. Legacy var aliases keep the SVG diagrams re-theming for free.
   ============================================================================ */

/* ---------------------------------------------------------------- TOKENS ---- */
:root{
  color-scheme: light;

  /* fonts -------------------------------------------------------------------- */
  --font-sans:"IBM Plex Sans",system-ui,-apple-system,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;
  --font-serif:"IBM Plex Serif","Iowan Old Style",Charter,"Source Serif 4",Georgia,Cambria,"Times New Roman",serif;
  --font-mono:"IBM Plex Mono",ui-monospace,"SF Mono","JetBrains Mono","Cascadia Code",Menlo,Consolas,monospace;
  --font-body:var(--font-serif);
  --font-heading:var(--font-sans);
  /* legacy aliases */
  --sans:var(--font-sans); --serif:var(--font-serif); --mono:var(--font-mono);

  /* type scale (1.25 major third) ------------------------------------------- */
  --text-xs:.78rem; --text-sm:.875rem; --text-base:1rem; --text-md:1.075rem;
  --text-lg:1.2rem; --text-xl:1.5rem; --text-2xl:1.85rem; --text-3xl:2.3rem;
  --fluid-h1:clamp(1.95rem,1.5rem+1.9vw,2.5rem);
  --fluid-h2:clamp(1.5rem,1.3rem+0.9vw,1.85rem);
  --fluid-h3:clamp(1.22rem,1.12rem+0.45vw,1.45rem);
  --lead-body:1.68; --lead-tight:1.18; --lead-ui:1.45; --track-h:-0.012em;
  --measure:43rem;          /* prose column ≈70ch          */
  --measure-narrow:34rem;

  /* spacing & shape --------------------------------------------------------- */
  --s1:.25rem; --s2:.5rem; --s3:.75rem; --s4:1rem; --s5:1.5rem; --s6:2rem; --s7:3rem; --s8:4rem; --s9:6rem;
  --r-xs:3px; --r-sm:6px; --r-md:10px; --r-lg:16px; --r-full:9999px;
  --radius:var(--r-md); --radius-sm:var(--r-sm);     /* legacy */

  /* layout ------------------------------------------------------------------ */
  --topbar-h:3.5rem; --sb:17rem; --rail:14rem; --shell-max:92rem;

  /* motion ------------------------------------------------------------------ */
  --dur-fast:140ms; --dur:200ms; --dur-slow:320ms;
  --ease:cubic-bezier(.2,0,0,1); --ease-io:cubic-bezier(.4,0,.2,1);

  /* focus ------------------------------------------------------------------- */
  --focus-w:2px; --focus-off:2px;

  /* COLOR · light (hex fallback first, then OKLCH) --------------------------- */
  --bg-page:#fbfaf8;     --bg-page:oklch(98.5% .004 95);
  --bg-surface:#ffffff;  --bg-surface:oklch(100% 0 95);
  --bg-elevated:#ffffff; --bg-elevated:oklch(100% 0 95);
  --bg-sunken:#f3f1ec;   --bg-sunken:oklch(96% .006 95);

  --text-primary:#1b1a17;   --text-primary:oklch(22% .006 95);
  --text-secondary:#5a564e; --text-secondary:oklch(45% .008 95);
  --text-faint:#8a857a;     --text-faint:oklch(62% .008 95);
  --text-on-accent:#ffffff; --text-on-accent:oklch(99% 0 0);

  --border:#e6e2d9;        --border:oklch(91% .006 95);
  --border-strong:#cbc6ba; --border-strong:oklch(82% .008 95);

  --accent-primary:#2f62e8; --accent-primary:oklch(54% .18 258);
  --accent-teal:#0a8c86;    --accent-teal:oklch(57% .11 192);
  --accent-violet:#7a45d6;  --accent-violet:oklch(55% .19 295);
  --accent-warn:#b5560f;    --accent-warn:oklch(57% .15 55);
  --accent-green:#2f8f57;   --accent-green:oklch(57% .13 150);
  --accent-rose:#c5354b;    --accent-rose:oklch(55% .18 18);

  --tint-primary:#eaf0ff; --tint-primary:oklch(96% .03 258);
  --tint-teal:#e3f4f2;    --tint-teal:oklch(96% .03 192);
  --tint-violet:#f1ebfc;  --tint-violet:oklch(96% .03 295);
  --tint-warn:#fdecdd;    --tint-warn:oklch(95% .04 55);
  --tint-green:#e6f4ec;   --tint-green:oklch(96% .03 150);
  --tint-rose:#fcebed;    --tint-rose:oklch(96% .03 18);

  /* elevation · light */
  --shadow-xs:0 1px 2px rgba(20,20,18,.06);
  --shadow-sm:0 1px 2px rgba(20,20,18,.06),0 2px 4px rgba(20,20,18,.05);
  --shadow:0 2px 4px rgba(20,20,18,.06),0 8px 24px rgba(20,20,18,.09);
  --shadow-lg:0 8px 16px rgba(20,20,18,.10),0 24px 48px rgba(20,20,18,.16);
  --edge:inset 0 1px 0 rgba(255,255,255,.5);

  /* ---- legacy aliases (so existing markup + SVG diagrams re-theme free) ---- */
  --bg:var(--bg-page); --surface:var(--bg-surface); --surface2:var(--bg-sunken); --surface3:var(--border);
  --fg:var(--text-primary); --muted:var(--text-secondary); --faint:var(--text-faint);
  --border2:var(--border-strong); --code-bg:var(--bg-sunken);
  --accent:var(--accent-primary); --accent2:var(--accent-teal); --accent3:var(--accent-violet);
  --warn:var(--accent-warn); --ok:var(--accent-green); --rose:var(--accent-rose);
  --warn-bg:var(--tint-warn); --ok-bg:var(--tint-green); --acc-bg:var(--tint-primary);
  --acc2-bg:var(--tint-teal); --acc3-bg:var(--tint-violet); --note-bg:var(--bg-sunken); --def-bg:var(--tint-primary);
  --shadow-sm:var(--shadow-sm);
}
html[data-theme="dark"]{
  color-scheme: dark;
  --bg-page:#14151a;     --bg-page:oklch(17% .008 260);
  --bg-surface:#1b1d24;  --bg-surface:oklch(21% .009 260);
  --bg-elevated:#23262f; --bg-elevated:oklch(25% .010 260);
  --bg-sunken:#101116;   --bg-sunken:oklch(14% .008 260);

  --text-primary:#ecedf1;   --text-primary:oklch(93% .004 260);
  --text-secondary:#b3b6c0; --text-secondary:oklch(76% .008 260);
  --text-faint:#7e8290;     --text-faint:oklch(58% .010 260);
  --text-on-accent:#0c0d11; --text-on-accent:oklch(15% .01 260);

  --border:#2b2e38;        --border:oklch(28% .010 260);
  --border-strong:#3b3f4b; --border-strong:oklch(35% .012 260);

  --accent-primary:#7aa0ff; --accent-primary:oklch(72% .14 258);
  --accent-teal:#41c8be;    --accent-teal:oklch(76% .10 192);
  --accent-violet:#b694f5;  --accent-violet:oklch(74% .14 295);
  --accent-warn:#e8945a;    --accent-warn:oklch(74% .12 55);
  --accent-green:#5cc485;   --accent-green:oklch(76% .11 150);
  --accent-rose:#fb7185;    --accent-rose:oklch(72% .14 18);

  --tint-primary:#1a2236; --tint-primary:oklch(26% .05 258);
  --tint-teal:#11302e;    --tint-teal:oklch(26% .04 192);
  --tint-violet:#241a39;  --tint-violet:oklch(26% .05 295);
  --tint-warn:#2e2013;    --tint-warn:oklch(26% .05 55);
  --tint-green:#11271b;   --tint-green:oklch(26% .04 150);
  --tint-rose:#2e1820;    --tint-rose:oklch(26% .05 18);

  --shadow-xs:0 1px 2px rgba(0,0,0,.4);
  --shadow-sm:0 1px 2px rgba(0,0,0,.45),0 2px 4px rgba(0,0,0,.35);
  --shadow:0 2px 6px rgba(0,0,0,.5),0 10px 24px rgba(0,0,0,.42);
  --shadow-lg:0 8px 16px rgba(0,0,0,.55),0 24px 48px rgba(0,0,0,.5);
  --edge:inset 0 1px 0 rgba(255,255,255,.05);
}

/* ---------------------------------------------------------------- BASE ------ */
*{box-sizing:border-box}
html{scroll-behavior:smooth;scroll-padding-top:calc(var(--topbar-h) + 1.2rem)}
@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*::before,*::after{transition-duration:.01ms!important;animation-duration:.01ms!important}}
body{margin:0;background:var(--bg-page);color:var(--text-primary);
  font:var(--text-md)/var(--lead-body) var(--font-body);
  -webkit-font-smoothing:antialiased;text-rendering:optimizeLegibility;overflow-wrap:break-word;
  -webkit-text-size-adjust:100%;text-size-adjust:100%;font-feature-settings:"kern" 1,"liga" 1}
:focus-visible{outline:var(--focus-w) solid var(--accent-primary);outline-offset:var(--focus-off);border-radius:var(--r-xs)}
:focus:not(:focus-visible){outline:none}
::selection{background:color-mix(in oklab,var(--accent-primary) 24%,transparent)}
img,svg{max-width:100%}

/* ---------------------------------------------------------------- TOPBAR ---- */
#progress{position:fixed;top:0;left:0;height:2px;width:0;z-index:80;
  background:linear-gradient(90deg,var(--accent-primary),var(--accent-teal));transition:width .1s linear}
.topbar{position:sticky;top:0;z-index:60;display:flex;align-items:center;gap:.85rem;height:var(--topbar-h);
  padding:0 1.1rem;background:color-mix(in oklab,var(--bg-page) 82%,transparent);
  backdrop-filter:saturate(160%) blur(12px);border-bottom:1px solid var(--border);font-family:var(--font-sans)}
.topbar .brand{display:flex;align-items:center;gap:.6rem;font-weight:650;font-size:.92rem;color:var(--text-primary);text-decoration:none;white-space:nowrap;letter-spacing:-.01em}
.topbar .brand .logo{width:1.6rem;height:1.6rem;flex:none}
.topbar .brand small{display:block;font-weight:450;color:var(--text-faint);font-size:.68rem;letter-spacing:.02em}
.topbar .spacer{flex:1}
.topbar .seg{display:flex;gap:.1rem;background:var(--bg-sunken);border:1px solid var(--border);border-radius:var(--r-sm);padding:.18rem}
.topbar .seg a{color:var(--text-secondary);text-decoration:none;font-size:.8rem;font-weight:550;padding:.28rem .65rem;border-radius:calc(var(--r-sm) - 2px);white-space:nowrap;transition:color var(--dur-fast) var(--ease),background var(--dur-fast) var(--ease)}
.topbar .seg a:hover{color:var(--text-primary)}
.topbar .seg a.cur{color:var(--text-primary);background:var(--bg-surface);box-shadow:var(--shadow-xs)}
.iconbtn{cursor:pointer;border:1px solid var(--border);background:var(--bg-surface);color:var(--text-primary);
  border-radius:var(--r-sm);padding:.4rem .55rem;font-size:.9rem;font-family:var(--font-sans);line-height:1;
  display:inline-flex;align-items:center;gap:.4rem;transition:background var(--dur-fast) var(--ease),border-color var(--dur-fast) var(--ease)}
.iconbtn:hover{background:var(--bg-sunken);border-color:var(--border-strong)}
.iconbtn kbd,.kbd{font-family:var(--font-mono);font-size:.66rem;color:var(--text-secondary);background:var(--bg-sunken);
  border:1px solid var(--border);border-bottom-width:2px;border-radius:4px;padding:.05em .3em;line-height:1}
#searchbtn{min-width:10rem;justify-content:space-between;color:var(--text-faint);font-size:.8rem;font-weight:450}
#searchbtn:hover{color:var(--text-secondary)}
#menubtn{display:none}

/* ---------------------------------------------------------------- SHELL ----- */
.shell{display:grid;grid-template-columns:var(--sb) minmax(0,1fr);max-width:var(--shell-max);margin:0 auto}
.sidebar{position:sticky;top:var(--topbar-h);align-self:start;height:calc(100vh - var(--topbar-h));height:calc(100dvh - var(--topbar-h));overflow:auto;
  padding:1.4rem .7rem 3rem 1.2rem;border-right:1px solid var(--border);font-family:var(--font-sans);font-size:.83rem;
  scrollbar-width:thin}
.sidebar .homelink{display:inline-flex;gap:.4rem;align-items:center;color:var(--text-faint);text-decoration:none;font-weight:550;font-size:.76rem;padding:.25rem .5rem;border-radius:var(--r-sm)}
.sidebar .homelink:hover{color:var(--text-primary);background:var(--bg-sunken)}
.sidebar .refswitch{display:none}
.sidebar .secttl{font-weight:600;font-size:.66rem;letter-spacing:.1em;text-transform:uppercase;color:var(--text-faint);margin:1.1rem .5rem .4rem}
.sidebar nav ul{list-style:none;margin:0;padding:0}
.sidebar nav>ul>li>a{display:flex;gap:.6rem;align-items:baseline;color:var(--text-secondary);text-decoration:none;
  padding:.34rem .55rem;border-radius:var(--r-sm);border-left:2px solid transparent;line-height:1.3;
  transition:color var(--dur-fast) var(--ease),background var(--dur-fast) var(--ease)}
.sidebar nav a .n{font-family:var(--font-mono);font-size:.72rem;color:var(--text-faint);min-width:1.2rem;font-weight:500}
.sidebar nav>ul>li>a:hover{color:var(--text-primary);background:var(--bg-sunken)}
.sidebar nav>ul>li>a.cur{color:var(--accent-primary);background:var(--tint-primary);font-weight:600}
.sidebar nav>ul>li>a.cur .n{color:var(--accent-primary)}
.sidebar nav .sub{list-style:none;margin:.15rem 0 .5rem;padding:0}
.sidebar nav .sub a{display:block;padding:.2rem .55rem .2rem 1.95rem;font-size:.92em;color:var(--text-faint);text-decoration:none;border-left:2px solid var(--border);margin-left:.7rem}
.sidebar nav .sub a:hover{color:var(--text-primary)}
.sidebar nav .sub a.active{color:var(--accent-primary);border-left-color:var(--accent-primary);font-weight:600}

.main{min-width:0}
.modwrap{display:grid;grid-template-columns:minmax(0,1fr) var(--rail);gap:2.6rem;
  padding:2rem clamp(1.1rem,3.5vw,3.2rem) 4rem;max-width:76rem;margin:0 auto}
.rail{position:sticky;top:calc(var(--topbar-h) + 1.4rem);align-self:start;max-height:calc(100vh - var(--topbar-h) - 2.5rem);max-height:calc(100dvh - var(--topbar-h) - 2.5rem);overflow:auto;font-family:var(--font-sans);scrollbar-width:thin}
.rail .ttl{font-weight:600;font-size:.66rem;letter-spacing:.1em;text-transform:uppercase;color:var(--text-faint);margin:.2rem 0 .55rem}
.rail ul{list-style:none;margin:0;padding:0;font-size:.79rem;border-left:1px solid var(--border)}
.rail a{display:block;color:var(--text-faint);text-decoration:none;padding:.24rem .75rem;margin-left:-1px;border-left:2px solid transparent;line-height:1.35;transition:color var(--dur-fast) var(--ease)}
.rail a:hover{color:var(--text-primary)}
.rail a.active{color:var(--accent-primary);border-left-color:var(--accent-primary);font-weight:600}
.rail a.h3{padding-left:1.5rem;font-size:.95em}
.sidebar nav a,.rail a{overflow-wrap:anywhere}

/* ---------------------------------------------------------------- ARTICLE --- */
.article{max-width:52rem;min-width:0;counter-reset:figure}
.article>*{max-width:var(--measure)}
.article>figure.diagram,.article>.tablewrap{max-width:52rem}
.crumbs{font-family:var(--font-sans);font-size:.76rem;color:var(--text-faint);margin:0 0 1rem;display:flex;flex-wrap:wrap;gap:.4rem;align-items:center}
.crumbs a{color:var(--text-faint);text-decoration:none}
.crumbs a:hover{color:var(--accent-primary)}
.crumbs .sep{opacity:.6}
.eyebrow{font-family:var(--font-sans);font-size:.72rem;font-weight:600;letter-spacing:.09em;text-transform:uppercase;color:var(--accent-primary)}
.article h1{font-family:var(--font-heading);font-size:var(--fluid-h1);line-height:1.1;letter-spacing:-.02em;margin:.4rem 0 .5rem;font-weight:600}
.article .standfirst{font-family:var(--font-sans);font-size:1.1rem;color:var(--text-secondary);margin:.3rem 0 1.2rem;line-height:1.5;font-weight:400}
.article .meta{display:flex;flex-wrap:wrap;gap:.55rem;align-items:center;font-family:var(--font-sans);font-size:.74rem;color:var(--text-faint);margin:0 0 2rem;padding-bottom:1.2rem;border-bottom:1px solid var(--border)}
.article h2{font-family:var(--font-heading);font-size:var(--fluid-h2);line-height:var(--lead-tight);margin:3rem 0 .5rem;padding-top:.2rem;font-weight:600;letter-spacing:var(--track-h);scroll-margin-top:5rem}
.article h3{font-family:var(--font-heading);font-size:var(--fluid-h3);margin:2rem 0 .4rem;font-weight:600;letter-spacing:-.008em;scroll-margin-top:5rem}
.article h4{font-family:var(--font-sans);font-size:.8rem;margin:1.5rem 0 .3rem;font-weight:600;color:var(--text-secondary);text-transform:uppercase;letter-spacing:.06em}
.article h2 .anchor,.article h3 .anchor{opacity:0;text-decoration:none;color:var(--accent-primary);margin-left:.4rem;font-weight:400}
.article h2:hover .anchor,.article h3:hover .anchor{opacity:.65}
.article p{margin:.85rem 0}
.article p.lead{font-size:1.12rem;line-height:1.55;color:var(--text-primary)}
.article a{color:var(--accent-primary);text-decoration:underline;text-decoration-thickness:1px;text-underline-offset:.16em;
  text-decoration-color:color-mix(in oklab,var(--accent-primary) 35%,transparent);transition:text-decoration-color var(--dur-fast) var(--ease)}
.article a:hover{text-decoration-color:var(--accent-primary)}
.article strong{font-weight:600;color:var(--text-primary)}
.article em{font-style:italic}
.article ul,.article ol{margin:.7rem 0 1rem;padding-left:1.4rem}
.article li{margin:.35rem 0}
.article li::marker{color:var(--text-faint)}
.article blockquote{margin:1.3rem 0;padding:.4rem 1.2rem;border-left:3px solid var(--accent-teal);color:var(--text-secondary);font-style:italic}
.article blockquote p{margin:.35rem 0}
.article hr{border:none;border-top:1px solid var(--border);margin:2.6rem 0}
.article code{font-family:var(--font-mono);font-size:.86em;background:var(--bg-sunken);padding:.12em .38em;border-radius:var(--r-xs);border:1px solid color-mix(in oklab,var(--border) 60%,transparent)}
.article pre{background:var(--bg-sunken);border:1px solid var(--border);border-radius:var(--r-md);padding:1rem 1.15rem;overflow:auto;font-size:.88rem;position:relative}
.article pre code{background:none;border:none;padding:0;font-size:.95em}
.copybtn{position:absolute;top:.5rem;right:.5rem;font-family:var(--font-sans);font-size:.68rem;font-weight:600;color:var(--text-secondary);
  background:var(--bg-surface);border:1px solid var(--border);border-radius:var(--r-sm);padding:.2rem .5rem;cursor:pointer;opacity:0;transition:opacity var(--dur) var(--ease)}
.article pre:hover .copybtn,.copybtn:focus-visible{opacity:1}

/* math */
.math.display{display:block;overflow-x:auto;overflow-y:hidden;margin:1.5rem 0;padding:.2rem 0;max-width:none}
mjx-container[display="true"]{margin:1.4rem 0!important}
mjx-container{overflow-x:auto;overflow-y:hidden;max-width:100%}

/* ---------------------------------------------------------------- CALLOUTS -- */
.callout{position:relative;margin:1.5rem 0;padding:.95rem 1.1rem .95rem 2.9rem;
  border:1px solid var(--border);border-left:3px solid var(--cc,var(--accent-primary));
  border-radius:0 var(--r-md) var(--r-md) 0;background:var(--cbg,var(--bg-sunken));font-size:.98rem;line-height:1.6}
.callout::before{content:var(--icon,"•");position:absolute;left:.85rem;top:.86rem;font-size:1.05rem;line-height:1;opacity:.95}
.callout>:first-child{margin-top:0}.callout>:last-child{margin-bottom:0}
.callout>p:first-child>strong:first-child{color:var(--cc,var(--accent-primary));font-family:var(--font-sans);font-size:.86em;font-weight:600;letter-spacing:.01em;text-transform:uppercase}
.callout.intuition {--cc:var(--accent-teal);  --cbg:var(--tint-teal);  --icon:"\1F4A1"}
.callout.definition{--cc:var(--accent-primary);--cbg:var(--tint-primary);--icon:"\1F4D0"}
.callout.theorem   {--cc:var(--accent-violet);--cbg:var(--tint-violet);--icon:"\03A3"}
.callout.example   {--cc:var(--accent-green); --cbg:var(--tint-green); --icon:"\1F9EA"}
.callout.synthesis {--cc:var(--accent-green); --cbg:var(--tint-green); --icon:"\1F517"}
.callout.pitfall   {--cc:var(--accent-warn);  --cbg:var(--tint-warn);  --icon:"\26A0"}
.callout.note      {--cc:var(--text-faint);   --cbg:var(--bg-sunken);  --icon:"\1F4DD"}
.callout.key       {--cc:var(--accent-primary);--cbg:var(--tint-primary);--icon:"\1F511"}
.callout.bridge    {--cc:var(--accent-rose);  --cbg:var(--tint-rose);  --icon:"\1F309"}
.callout.history   {--cc:var(--text-faint);   --cbg:var(--bg-sunken);  --icon:"\1F4DC"}

/* progressive disclosure */
details.disc{margin:1.4rem 0;border:1px solid var(--border);border-radius:var(--r-md);background:var(--bg-surface);overflow:hidden}
details.disc>summary{cursor:pointer;padding:.7rem 1rem;font-family:var(--font-sans);font-weight:600;font-size:.86rem;color:var(--accent-primary);list-style:none;display:flex;gap:.5rem;align-items:center}
details.disc>summary::-webkit-details-marker{display:none}
details.disc>summary::before{content:"\25B8";transition:transform var(--dur) var(--ease);color:var(--text-faint)}
details.disc[open]>summary::before{transform:rotate(90deg)}
details.disc>summary:hover{background:var(--bg-sunken)}
details.disc .body{padding:.4rem 1.15rem 1rem;border-top:1px solid var(--border)}

/* ---------------------------------------------------------------- TABLES ---- */
.tablewrap{overflow:auto;margin:1.6rem 0;border:1px solid var(--border);border-radius:var(--r-md)}
.article table{border-collapse:collapse;width:100%;font-family:var(--font-sans);font-size:.84rem;line-height:1.45;font-variant-numeric:tabular-nums}
.article table th,.article table td{text-align:left;padding:.55rem .8rem;border-bottom:1px solid var(--border);vertical-align:top}
.article table thead th{background:var(--bg-sunken);font-weight:600;position:sticky;top:0;z-index:1;color:var(--text-primary)}
.article table tbody tr:last-child td{border-bottom:none}
.article table tbody tr:hover td{background:color-mix(in oklab,var(--bg-sunken) 50%,transparent)}
.article table code{font-size:.92em}

/* ---------------------------------------------------------------- FIGURES --- */
figure.diagram{counter-increment:figure;margin:2rem 0;padding:1.3rem 1.3rem 1rem;background:var(--bg-surface);
  border:1px solid var(--border);border-radius:var(--r-lg);box-shadow:var(--shadow-xs);text-align:center;color:var(--text-primary)}
figure.diagram svg{height:auto;display:block;margin:0 auto}
figure.diagram figcaption{margin-top:1rem;padding-top:.75rem;border-top:1px solid var(--border);color:var(--text-secondary);font-family:var(--font-sans);font-size:.78rem;line-height:1.5;text-align:left}
figure.diagram figcaption::before{content:"Fig. " counter(figure) "  ·  ";font-weight:600;color:var(--accent-primary)}
figure.diagram figcaption .tag{font-weight:600;color:var(--text-primary)}
.diagram text{font-family:var(--font-sans);font-size:13px;fill:var(--fg)}
.diagram .sm{font-size:11px}.diagram .bg{font-size:15px;font-weight:600}
.diagram .mut{fill:var(--muted)}.diagram .ac{fill:var(--accent)}.diagram .ac2{fill:var(--accent2)}.diagram .wn{fill:var(--warn)}.diagram .ac3{fill:var(--accent3)}
.diagram .b{font-weight:600}.diagram .i{font-style:italic}
.diagram .box{fill:var(--bg-sunken);stroke:var(--border-strong);stroke-width:1.5}
.diagram .boxac{fill:color-mix(in oklab,var(--accent) 12%,var(--bg-surface));stroke:var(--accent);stroke-width:1.8}
.diagram .boxac2{fill:color-mix(in oklab,var(--accent2) 14%,var(--bg-surface));stroke:var(--accent2);stroke-width:1.8}
.diagram .boxac3{fill:color-mix(in oklab,var(--accent3) 14%,var(--bg-surface));stroke:var(--accent3);stroke-width:1.8}
.diagram .ln{stroke:var(--fg);stroke-width:1.6;fill:none}
.diagram .lnac{stroke:var(--accent);stroke-width:2;fill:none}
.diagram .lnac2{stroke:var(--accent2);stroke-width:2;fill:none}
.diagram .lnac3{stroke:var(--accent3);stroke-width:2;fill:none}
.diagram .lnmut{stroke:var(--muted);stroke-width:1.3;fill:none}
.diagram .axis{stroke:var(--muted);stroke-width:1.3;fill:none}
.diagram .grid{stroke:var(--border);stroke-width:1;fill:none}
.diagram .dash{stroke-dasharray:5 4}.diagram .dot{stroke-dasharray:1.5 3}
.diagram .soft{fill:var(--accent);opacity:.12}.diagram .soft2{fill:var(--accent2);opacity:.12}.diagram .softw{fill:var(--warn);opacity:.13}.diagram .soft3{fill:var(--accent3);opacity:.12}
#arr path{fill:var(--fg)}#arrac path{fill:var(--accent)}#arrac2 path{fill:var(--accent2)}#arrac3 path{fill:var(--accent3)}#arrm path{fill:var(--muted)}

/* ---------------------------------------------------------------- PAGER ----- */
.pager{display:grid;grid-template-columns:1fr 1fr;gap:1rem;margin:3.5rem 0 0;max-width:52rem;font-family:var(--font-sans)}
.pager a{display:flex;flex-direction:column;gap:.25rem;padding:1rem 1.15rem;border:1px solid var(--border);border-radius:var(--r-md);text-decoration:none;color:var(--text-primary);background:var(--bg-surface);transition:border-color var(--dur) var(--ease),box-shadow var(--dur) var(--ease)}
.pager a:hover{border-color:var(--accent-primary);box-shadow:var(--shadow-sm)}
.pager .dir{font-size:.72rem;color:var(--text-faint);font-weight:550}
.pager .ttl{font-weight:600;font-size:.95rem;color:var(--accent-primary)}
.pager a.next{text-align:right}
.pager a.disabled{visibility:hidden}

/* ---------------------------------------------------------------- FOOTER ---- */
.foot{max-width:52rem;margin:3rem 0 0;padding-top:1.5rem;border-top:1px solid var(--border);color:var(--text-faint);font-family:var(--font-sans);font-size:.8rem;line-height:1.65}
.foot a{color:var(--accent-primary);text-decoration:none}.foot a:hover{text-decoration:underline}
.foot .small{font-size:.73rem}

/* ---------------------------------------------------------------- HUB ------- */
.wide{max-width:74rem;margin:0 auto;padding:2rem clamp(1.1rem,4vw,3.2rem) 4rem}
.hero{padding:2rem 0 1.4rem;max-width:48rem}
.hero .eyebrow{margin-bottom:.6rem;display:block}
.hero h1{font-family:var(--font-heading);font-size:clamp(2.1rem,4.4vw,3.1rem);line-height:1.06;letter-spacing:-.025em;margin:.15rem 0 .7rem;font-weight:600}
.hero p.sub{font-family:var(--font-sans);font-size:1.18rem;color:var(--text-secondary);max-width:42rem;line-height:1.55;margin:.3rem 0 1.3rem;font-weight:400}
.hero .cta{display:flex;flex-wrap:wrap;gap:.65rem;margin-top:.4rem}
.btn{font-family:var(--font-sans);font-weight:550;font-size:.88rem;text-decoration:none;padding:.62rem 1.15rem;border-radius:var(--r-sm);border:1px solid var(--border-strong);color:var(--text-primary);background:var(--bg-surface);display:inline-flex;gap:.45rem;align-items:center;transition:border-color var(--dur) var(--ease),background var(--dur) var(--ease)}
.btn:hover{border-color:var(--accent-primary)}
.btn.primary{background:var(--accent-primary);color:var(--text-on-accent);border-color:var(--accent-primary)}
.btn.primary:hover{filter:brightness(1.06)}

.sectionhead{font-family:var(--font-heading);font-size:1.35rem;font-weight:600;margin:3rem 0 .3rem;letter-spacing:-.015em}
.sectionsub{color:var(--text-secondary);font-family:var(--font-sans);font-size:.9rem;margin:0 0 1.2rem}

.cardgrid{display:grid;grid-template-columns:repeat(auto-fill,minmax(min(17.5rem,100%),1fr));gap:1.1rem}
.card{position:relative;display:flex;flex-direction:column;gap:.55rem;padding:1.2rem 1.25rem 1.3rem;border:1px solid var(--border);border-radius:var(--r-lg);background:var(--bg-surface);text-decoration:none;color:var(--text-primary);transition:border-color var(--dur) var(--ease),box-shadow var(--dur) var(--ease),transform var(--dur) var(--ease)}
.card::after{content:"";position:absolute;inset:0;border-radius:inherit;box-shadow:var(--edge);pointer-events:none}
.card:hover{border-color:var(--accent-primary);box-shadow:var(--shadow);transform:translateY(-2px)}
.card .num{font-family:var(--font-mono);font-size:.74rem;font-weight:600;color:var(--text-on-accent);background:var(--accent-primary);width:1.8rem;height:1.8rem;border-radius:var(--r-sm);display:grid;place-items:center}
.card.mat .num{background:var(--accent-rose)}
.card h3{font-family:var(--font-heading);font-size:1.05rem;font-weight:600;margin:.15rem 0 0;line-height:1.25;letter-spacing:-.01em}
.card p{font-family:var(--font-sans);font-size:.84rem;color:var(--text-secondary);margin:0;line-height:1.5}
.card .chips{margin-top:auto;display:flex;flex-wrap:wrap;gap:.32rem;padding-top:.35rem}
.chip{font-family:var(--font-sans);font-size:.68rem;font-weight:550;color:var(--text-secondary);background:var(--bg-sunken);border:1px solid var(--border);border-radius:var(--r-full);padding:.12rem .55rem;white-space:nowrap}
.chip.p{color:var(--accent-primary);border-color:color-mix(in oklab,var(--accent-primary) 30%,var(--border))}
.chip.rd{color:var(--accent-violet);border-color:color-mix(in oklab,var(--accent-violet) 30%,var(--border))}

.refpick{display:grid;grid-template-columns:1fr 1fr;gap:1.3rem;margin:1.6rem 0}
.refcard{position:relative;display:flex;flex-direction:column;gap:.65rem;padding:1.7rem;border:1px solid var(--border);border-radius:var(--r-lg);background:var(--bg-surface);text-decoration:none;color:var(--text-primary);transition:border-color var(--dur) var(--ease),box-shadow var(--dur) var(--ease),transform var(--dur) var(--ease)}
.refcard:hover{border-color:var(--accent-primary);box-shadow:var(--shadow);transform:translateY(-3px)}
.refcard .ico{width:2.8rem;height:2.8rem}
.refcard h2{font-family:var(--font-heading);font-size:1.35rem;margin:.25rem 0 0;font-weight:600;letter-spacing:-.015em}
.refcard p{font-family:var(--font-sans);font-size:.92rem;color:var(--text-secondary);margin:0;line-height:1.55}
.refcard .go{font-family:var(--font-sans);font-weight:600;font-size:.85rem;color:var(--accent-primary);margin-top:.35rem}

.paths{display:grid;grid-template-columns:repeat(auto-fit,minmax(min(15.5rem,100%),1fr));gap:1.1rem}
.path{padding:1.1rem 1.2rem;border:1px solid var(--border);border-radius:var(--r-md);background:var(--bg-sunken)}
.path h4{font-family:var(--font-heading);font-size:.95rem;font-weight:600;margin:0 0 .35rem;color:var(--text-primary)}
.path p{font-family:var(--font-sans);font-size:.8rem;color:var(--text-secondary);margin:0 0 .6rem;line-height:1.5}
.path .seq{font-family:var(--font-sans);font-size:.78rem;display:flex;flex-wrap:wrap;gap:.3rem;align-items:center}
.path .seq a{text-decoration:none;color:var(--accent-primary);font-weight:550}
.path .seq a:hover{text-decoration:underline}
.path .seq .arr{color:var(--text-faint)}

/* ---------------------------------------------------------------- SEARCH ---- */
#searchwrap{position:fixed;inset:0;z-index:90;display:none;background:color-mix(in oklab,#0a0a0c 55%,transparent);backdrop-filter:blur(3px);padding:9vh 1rem 1rem}
#searchwrap.open{display:block}
.searchbox{max-width:40rem;margin:0 auto;background:var(--bg-elevated);border:1px solid var(--border-strong);border-radius:var(--r-lg);box-shadow:var(--shadow-lg);overflow:hidden}
.searchbox input{width:100%;border:none;outline:none;background:none;color:var(--text-primary);font-family:var(--font-sans);font-size:1.05rem;padding:1.05rem 1.25rem;border-bottom:1px solid var(--border)}
.searchbox input::placeholder{color:var(--text-faint)}
#searchresults{max-height:60vh;max-height:60dvh;overflow:auto;padding:.45rem}
#searchresults .res{display:block;padding:.6rem .85rem;border-radius:var(--r-sm);text-decoration:none;color:var(--text-primary)}
#searchresults .res:hover,#searchresults .res.sel{background:var(--bg-sunken)}
#searchresults .res .t{font-family:var(--font-sans);font-weight:600;font-size:.92rem}
#searchresults .res .c{font-family:var(--font-sans);font-size:.77rem;color:var(--text-secondary);margin-top:.1rem}
#searchresults .res mark{background:color-mix(in oklab,var(--accent-primary) 26%,transparent);color:inherit;border-radius:2px;padding:0 .05em}
#searchresults .res .badge{font-family:var(--font-sans);font-size:.65rem;font-weight:600;color:var(--accent-primary);text-transform:uppercase;letter-spacing:.05em}
#searchresults .empty{padding:1.3rem;color:var(--text-secondary);font-family:var(--font-sans);font-size:.85rem;text-align:center}
.searchfoot{display:flex;gap:1.1rem;padding:.55rem .95rem;border-top:1px solid var(--border);font-family:var(--font-sans);font-size:.72rem;color:var(--text-faint)}

/* ---------------------------------------------------------------- RESPONSIVE */
/* >1180: full 3-col (sidebar + article + on-this-page rail) */
@media (max-width:1180px){:root{--rail:0px}.modwrap{grid-template-columns:minmax(0,1fr)}.rail{display:none}}
/* <=920: sidebar collapses to an off-canvas drawer */
@media (max-width:920px){
  :root{--sb:0px}
  #menubtn{display:inline-flex}
  .shell{grid-template-columns:1fr}
  .sidebar{position:fixed;left:0;top:0;height:100vh;height:100dvh;width:18.5rem;max-width:85vw;z-index:95;background:var(--bg-surface);
    transform:translateX(-104%);transition:transform var(--dur-slow) var(--ease);box-shadow:var(--shadow-lg);padding-top:1.2rem;border-right:1px solid var(--border)}
  .sidebar.open{transform:none}
  .sidebar nav>ul>li>a{padding-top:.5rem;padding-bottom:.5rem}   /* comfortable tap targets */
  .sidebar nav .sub a{padding-top:.4rem;padding-bottom:.4rem}
  .sidebar .refswitch{display:flex;gap:.25rem;margin:.4rem .4rem .6rem;background:var(--bg-sunken);border:1px solid var(--border);border-radius:var(--r-sm);padding:.2rem}
  .sidebar .refswitch a{flex:1;text-align:center;text-decoration:none;color:var(--text-secondary);font-weight:600;font-size:.82rem;padding:.4rem;border-radius:calc(var(--r-sm) - 2px)}
  .sidebar .refswitch a.cur{background:var(--bg-surface);color:var(--accent-primary);box-shadow:var(--shadow-xs)}
  body.navopen::after{content:"";position:fixed;inset:0;background:rgba(0,0,0,.5);z-index:90}
  .topbar .seg{display:none}
  .iconbtn{padding:.5rem .6rem}
  .refpick{grid-template-columns:1fr}.pager{grid-template-columns:1fr}
  #searchbtn span.lbl{display:none}#searchbtn{min-width:auto}
}
/* <=640: keep wide diagrams legible (scroll within the figure rather than shrink to nothing) */
@media (max-width:640px){
  .modwrap{gap:2rem}
  figure.diagram{padding:1rem .85rem .85rem;overflow-x:auto}
  figure.diagram svg{min-width:30rem}
  .wide{padding-top:1.4rem}
}
/* <=520: phones — tighten chrome, shrink the brand */
@media (max-width:520px){
  body{font-size:1rem}
  .article h1,.hero h1{letter-spacing:-.02em}
  .modwrap{padding-left:1.1rem;padding-right:1.1rem}
  .topbar{gap:.5rem;padding:0 .7rem}
  .topbar .brand small{display:none}
  .article .meta{gap:.4rem}
}
/* <=380: very small — logo only in the brand */
@media (max-width:380px){
  .topbar .brand span{display:none}
}
/* touch / no-hover devices: reveal hover-only affordances */
@media (hover:none){
  .copybtn{opacity:1}
  .article h2 .anchor,.article h3 .anchor{opacity:.45}
}

/* ---------------------------------------------------------------- PRINT ----- */
@media print{
  .topbar,.sidebar,.rail,#progress,#menubtn,.iconbtn,.pager,#searchwrap,.copybtn{display:none!important}
  .shell,.modwrap{display:block;max-width:none;padding:0}
  .article,.article>*{max-width:none}
  body{font-size:11pt;background:#fff;color:#000}
  figure.diagram,.tablewrap,.callout,.card{box-shadow:none;break-inside:avoid}
  .article h2,.article h3{break-after:avoid}
  .article a{color:#000;text-decoration:underline}
}