:root{
  --void:#070a12; --slab:#0d1320; --slab2:#111a2b; --edge:#1d2940;
  --glass:#e8eef7; --dim:#8d9cb5; --blue:#3b82f6; --blue2:#60a5fa; --blueglow:rgba(59,130,246,.14);
  --rise:#34d399; --fall:#f87171;
  --display:'Spectral',Georgia,'Times New Roman',serif;
  --text:'IBM Plex Sans',system-ui,-apple-system,sans-serif;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;background:var(--void);color:var(--glass);font-family:var(--text);
  line-height:1.66;font-size:16.5px;-webkit-font-smoothing:antialiased}
.fts-shell{max-width:1020px;margin:0 auto;padding:0 22px}
a{color:var(--blue2);text-decoration:none}
a:hover{text-decoration:underline}
h1,h2,h3{font-family:var(--display);line-height:1.18;font-weight:600;color:#f4f7fc}
h1{letter-spacing:-.015em}
h2{font-size:clamp(1.42rem,2.6vw,1.95rem);margin:0 0 .5em}
h3{font-size:1.14rem;margin:1.5em 0 .35em;color:#eef3fa}
p{margin:.78em 0}
.fts-dim{color:var(--dim)}
section{padding:46px 0}
section + section{border-top:1px solid var(--edge)}
.fts-tag{font-family:var(--text);font-weight:600;font-size:.72rem;letter-spacing:.2em;
  text-transform:uppercase;color:var(--blue2);margin-bottom:13px}
/* top bar */
.fts-bar{position:sticky;top:0;z-index:50;display:flex;align-items:center;justify-content:space-between;
  gap:18px;padding:13px 22px;background:rgba(7,10,18,.88);backdrop-filter:blur(10px);
  border-bottom:1px solid var(--edge)}
.fts-brand{display:flex;align-items:center;gap:9px;font-family:var(--display);font-weight:600;
  font-size:1.05rem;color:#f4f7fc}
.fts-brand .pip{width:9px;height:9px;border-radius:50%;background:var(--blue);box-shadow:0 0 11px var(--blue)}
.fts-nav{display:flex;gap:21px;list-style:none;margin:0;padding:0;font-size:.92rem}
.fts-nav a{color:var(--dim)}
.fts-nav a:hover{color:var(--glass);text-decoration:none}
.fts-pill{border:1px solid var(--blue);color:var(--blue2)!important;padding:8px 14px;border-radius:7px;
  font-weight:600;font-size:.86rem}
.fts-pill:hover{background:var(--blueglow);text-decoration:none}
.fts-hamb{display:none;background:none;border:0;cursor:pointer;width:30px;height:24px}
.fts-hamb span{display:block;height:2px;background:var(--glass);margin:5px 0;border-radius:2px}
.fts-sheet{display:none;flex-direction:column;padding:6px 22px 18px;border-bottom:1px solid var(--edge);
  background:var(--slab)}
.fts-sheet a{color:var(--glass);padding:11px 0;border-bottom:1px solid var(--edge);font-size:1rem}
.fts-sheet.open{display:flex}
/* lead / opening */
.fts-lead{padding:62px 0 42px;background:radial-gradient(120% 80% at 20% 0%,var(--slab2),var(--void) 60%)}
.fts-kick{font-family:var(--text);font-weight:600;font-size:.76rem;letter-spacing:.18em;
  text-transform:uppercase;color:var(--blue2)}
.fts-lead h1{font-size:clamp(2.05rem,4.5vw,3rem);margin:.32em 0 .35em;max-width:19ch}
.fts-strap{font-size:1.16rem;color:#c6d2e5;max-width:63ch}
.fts-chips{display:flex;flex-wrap:wrap;gap:10px;margin-top:25px;font-size:.86rem}
.fts-chip{background:var(--slab);border:1px solid var(--edge);border-radius:8px;padding:8px 13px;color:var(--dim)}
.fts-chip b{color:var(--blue2);font-weight:600}
.fts-go{display:inline-block;margin-top:27px;background:var(--blue);color:#06122c;font-weight:700;
  padding:13px 23px;border-radius:8px;font-size:.96rem}
.fts-go:hover{background:var(--blue2);text-decoration:none}
.fts-body-lead{font-size:1.08rem;color:#cdd8ea;max-width:66ch}
/* panels & cards */
.fts-slab{background:var(--slab);border:1px solid var(--edge);border-radius:13px;padding:24px 26px;margin:20px 0}
.fts-slab.cast{border-color:#28406b;box-shadow:0 0 0 1px var(--blueglow) inset}
.fts-grid{display:grid;gap:17px}
@media(min-width:720px){.fts-g3{grid-template-columns:repeat(3,1fr)}.fts-g2{grid-template-columns:1fr 1fr}}
.fts-card{background:var(--slab);border:1px solid var(--edge);border-radius:12px;padding:21px}
.fts-card h3{margin-top:0}
.fts-num{font-family:var(--display);font-size:1.5rem;color:var(--blue2);font-weight:600;line-height:1}
.fts-mark{font-family:var(--text);font-size:.7rem;font-weight:700;letter-spacing:.13em;
  text-transform:uppercase;color:var(--blue2)}
/* checklist */
.fts-list{list-style:none;padding:0;margin:18px 0}
.fts-list li{position:relative;padding:11px 0 11px 28px;border-bottom:1px solid var(--edge);color:#cdd8ea}
.fts-list li:before{content:"";position:absolute;left:5px;top:18px;width:8px;height:8px;
  border:2px solid var(--blue);border-radius:50%}
/* record table */
.fts-scroll{overflow-x:auto;margin:20px 0}
table{border-collapse:collapse;width:100%;font-size:.92rem;min-width:520px}
caption{caption-side:bottom;text-align:left;color:var(--dim);font-size:.83rem;padding-top:11px}
th,td{padding:12px 14px;border-bottom:1px solid var(--edge);text-align:left}
thead th{font-family:var(--text);font-size:.71rem;letter-spacing:.09em;text-transform:uppercase;
  color:var(--dim);font-weight:600}
tbody tr.lit td{background:var(--blueglow)}
td .up{color:var(--rise);font-weight:600}
/* crumb + prose */
.fts-crumb{font-size:.83rem;color:var(--dim);padding:17px 0 0}
.fts-crumb a{color:var(--dim)}
.fts-crumb .pt{opacity:.5;margin:0 6px}
.fts-sub{font-size:1.15rem;color:#c6d2e5;max-width:64ch;margin:.5em 0 0}
.fts-prose h2{font-size:1.14rem;margin:1.5em 0 .35em;color:var(--blue2)}
.fts-prose h2:first-child{margin-top:0}
.fts-prose h3{color:var(--blue2)}
.fts-prose code{font-family:'IBM Plex Mono',ui-monospace,SFMono-Regular,Menlo,monospace;font-size:.85em;
  background:var(--slab2);padding:2px 6px;border-radius:4px;color:var(--blue2)}
.fts-pull{border-left:3px solid var(--blue);background:var(--blueglow);padding:6px 0 6px 16px;
  margin:20px 0;color:#cdd8ea;font-size:.95rem}
/* footer */
.fts-foot{border-top:1px solid var(--edge);background:var(--slab2);margin-top:32px;padding:42px 0 30px}
.fts-foot .row{display:grid;gap:23px}
@media(min-width:720px){.fts-foot .row{grid-template-columns:2fr 1fr 1fr 1fr}}
.fts-foot a{color:var(--dim);display:block;padding:3px 0}
.fts-foot a:hover{color:var(--blue2)}
.fts-foot .cap{color:#f4f7fc;font-family:var(--display);font-size:.97rem;font-weight:600;margin-bottom:10px}
.fts-fine{color:#6b7c97;font-size:.82rem;margin-top:25px;border-top:1px solid var(--edge);padding-top:17px}
/* worked-example callout: a framed teaching block, distinct from .fts-pull and from sibling .worked */
.fts-worked{background:var(--slab2);border:1px solid var(--edge);border-left:3px solid var(--blue);
  border-radius:0 12px 12px 0;padding:19px 22px;margin:22px 0}
.fts-worked .fts-mark{margin-bottom:11px}
.fts-worked ol{margin:0;padding-left:21px}
.fts-worked ol li{padding:7px 0;color:#cdd8ea}
.fts-worked ol li b{color:#f4f7fc}
.fts-worked p{color:#cdd8ea}
.fts-worked code,.fts-prose code{font-family:'IBM Plex Mono',ui-monospace,SFMono-Regular,Menlo,monospace;
  font-size:.85em;background:#0a1020;border:1px solid var(--edge);border-radius:4px;padding:1px 6px;
  color:var(--blue2);word-break:break-word}
/* on-brand inline diagram frame (distinct .fts-dgm namespace; siblings use .diagram) */
figure.fts-dgm{margin:26px 0;background:var(--slab);border:1px solid var(--edge);border-radius:13px;
  padding:18px 18px 12px}
figure.fts-dgm svg{display:block;width:100%;height:auto;max-width:780px;margin:0 auto}
figure.fts-dgm figcaption{font-size:.82rem;color:var(--dim);text-align:center;margin-top:11px;max-width:62ch;
  margin-left:auto;margin-right:auto}
.fts-dgm .g-box{fill:var(--slab2,#111a2b);stroke:#28406b;stroke-width:1.2}
.fts-dgm .g-edge{stroke:var(--blue);stroke-width:1.6;fill:none}
.fts-dgm .g-h{font-family:'Spectral',serif;font-size:12.5px;fill:#f4f7fc;font-weight:600}
.fts-dgm .g-t{font-family:'IBM Plex Sans',sans-serif;font-size:9.5px;fill:#8d9cb5}
.fts-dgm .g-ax{font-family:'IBM Plex Mono',monospace;font-size:10px;fill:#8d9cb5}
.fts-dgm .g-up{stroke:var(--rise);stroke-width:1.7;fill:none}
.fts-dgm .g-dn{stroke:var(--fall);stroke-width:1.7;fill:none}
.fts-dgm .g-band{stroke:var(--blue2);stroke-width:1.1;stroke-dasharray:4 4;fill:none}
.fts-dgm .g-lab{font-family:'IBM Plex Mono',monospace;font-size:9.5px;font-weight:600}
.fts-dgm .g-good{fill:var(--rise);font-family:'IBM Plex Mono',monospace;font-size:13px;font-weight:700}
.fts-dgm .g-bad{fill:var(--fall);font-family:'IBM Plex Mono',monospace;font-size:13px;font-weight:700}
/* per-model grade-bar table accent */
.fts-gbar{font-family:'IBM Plex Mono',monospace;color:var(--blue2)}
/* related block at a leaf/hub foot (distinct .fts-rel namespace) */
.fts-rel{margin:32px 0 0;border-top:1px solid var(--edge);padding-top:21px}
.fts-rel .hd{font-size:.74rem;letter-spacing:.18em;text-transform:uppercase;color:var(--blue2);margin-bottom:13px;font-weight:600}
.fts-rel .lk{display:grid;gap:11px}
@media(min-width:620px){.fts-rel .lk{grid-template-columns:1fr 1fr}}
.fts-rel a.rl{display:block;border:1px solid var(--edge);border-radius:10px;padding:13px 15px;background:var(--slab);color:var(--glass)}
.fts-rel a.rl:hover{border-color:#28406b;text-decoration:none}
.fts-rel a.rl b{color:var(--blue2);display:block;font-size:.95rem}
.fts-rel a.rl span{color:var(--dim);font-size:.84rem}
@media(max-width:719px){.fts-nav{display:none}.fts-hamb{display:block}}

/* a11y + responsive polish */
:focus-visible{outline:2px solid currentColor;outline-offset:3px;border-radius:3px}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*{animation-duration:.01ms !important;transition-duration:.01ms !important}}
@media(max-width:719px){table{min-width:0}th,td{padding:8px 10px}}