/* 1080 Learner research paper (web edition). Same design family as /1080-demo/ (SPEC-1080-v2 1.2 tokens).
   Fonts are the demo's self-hosted WOFF2 files, reused by URL. No inline styles or scripts anywhere (live CSP). */
@font-face { font-family: "Instrument Serif"; src: url(/1080-demo/fonts/InstrumentSerif-latin.woff2?v=1) format("woff2"); font-weight: 400; font-style: normal; font-display: swap; }
@font-face { font-family: "Instrument Sans"; src: url(/1080-demo/fonts/InstrumentSans-latin.woff2?v=1) format("woff2"); font-weight: 400 700; font-style: normal; font-display: swap; }
@font-face { font-family: "IBM Plex Mono"; src: url(/1080-demo/fonts/IBMPlexMono-400-latin.woff2?v=1) format("woff2"); font-weight: 400 600; font-style: normal; font-display: swap; }
@font-face { font-family: "Serif Fallback"; src: local("Times New Roman"), local("Times"); size-adjust: 83.4%; ascent-override: 118.7%; descent-override: 37.2%; line-gap-override: 0%; }
@font-face { font-family: "Sans Fallback"; src: local("Arial"), local("Helvetica"); size-adjust: 101.2%; ascent-override: 95.8%; descent-override: 24.7%; line-gap-override: 0%; }

:root {
  --ink: #141823; --stone: #F2EEE8; --paper: #FBF9F5; --cobalt: #2346D8; --aqua: #3FC1E8; --aqua-t: #0B6E86;
  --terra: #C8643B; --terra-t: #A84A24; --meta: #5B6474; --line: rgba(20, 24, 35, .12); --line-2: rgba(20, 24, 35, .22);
  --spectral: linear-gradient(90deg, #6E4BF2 0%, #2346D8 24%, #3FC1E8 50%, #F0B23C 76%, #E0702C 100%);
  --serif: "Instrument Serif", "Serif Fallback", Georgia, serif;
  --sans: "Instrument Sans", "Sans Fallback", Arial, system-ui, sans-serif;
  --mono: "IBM Plex Mono", ui-monospace, "Cascadia Mono", Consolas, monospace;
  --ease: cubic-bezier(.2, .8, .2, 1); --wrap: 1240px; --gut: clamp(18px, 4vw, 44px);
  --shadow: 0 1px 0 rgba(255, 255, 255, .9) inset, 0 24px 48px -28px rgba(20, 24, 35, .38), 0 2px 6px -2px rgba(20, 24, 35, .08);
  color-scheme: light;
}
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-padding-top: 84px; scroll-behavior: smooth; }
body { margin: 0; background: var(--stone); color: var(--ink); font: 400 1.0625rem/1.66 var(--sans); text-rendering: optimizeLegibility; }
img, svg { max-width: 100%; }
a { color: var(--cobalt); text-underline-offset: .18em; text-decoration-thickness: 1px; }
a:hover { text-decoration-thickness: 2px; }
:focus-visible { outline: 3px solid var(--cobalt); outline-offset: 3px; border-radius: 4px; }
.sr-only { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
.skip { position: absolute; left: 12px; top: -60px; z-index: 100; background: var(--ink); color: var(--stone); padding: 12px 16px; border-radius: 10px; }
.skip:focus { top: 12px; }
.bx { font-family: "Segoe UI Symbol", "Apple Symbols", "DejaVu Sans", sans-serif; font-size: 1.08em; line-height: 1; }

/* reading progress: CSS scroll-driven, no script */
.progress { position: fixed; inset: 0 0 auto 0; height: 3px; z-index: 60; background: var(--spectral); transform-origin: 0 50%; transform: scaleX(0); }
@supports (animation-timeline: scroll()) {
  .progress { animation: grow linear both; animation-timeline: scroll(root); }
  @keyframes grow { to { transform: scaleX(1); } }
}

/* header */
.top { position: sticky; top: 0; z-index: 50; background: rgba(242, 238, 232, .86); backdrop-filter: saturate(1.4) blur(14px); -webkit-backdrop-filter: saturate(1.4) blur(14px); }
.top-in { max-width: var(--wrap); margin: 0 auto; padding: 12px var(--gut); display: flex; align-items: center; gap: 16px; }
.brand { display: flex; align-items: center; gap: 10px; color: var(--ink); text-decoration: none; font-weight: 600; letter-spacing: -.01em; }
.brand-mark { width: 30px; height: 30px; flex: none; }
.chip { margin: 0; font: 400 .75rem/1 var(--mono); color: var(--meta); display: none; align-items: center; gap: 8px; padding: 7px 11px; border: 1px solid var(--line-2); border-radius: 999px; }
.chip-dot { width: 7px; height: 7px; border-radius: 50%; background: var(--terra); }
.top-nav { margin-left: auto; display: flex; gap: 4px; align-items: center; }
.top-nav a { color: var(--ink); text-decoration: none; font-size: .9rem; padding: 8px 10px; border-radius: 8px; }
.top-nav a:hover { background: rgba(35, 70, 216, .08); }
.top-nav .top-cta { background: var(--ink); color: var(--stone); padding: 8px 14px; }
.top-nav .top-cta:hover { background: var(--cobalt); }
.hairline { height: 1px; background: var(--spectral); opacity: .85; }
@media (max-width: 560px) { .top-nav a:not(.top-cta):not(:first-child) { display: none; } }
@media (min-width: 900px) { .chip { display: inline-flex; } }

/* hero */
.hero { position: relative; overflow: hidden; background: #E9EEF5; }
.hero-art { position: relative; aspect-ratio: 3 / 2; }
.hero-art img { position: absolute; inset: 0; width: 100%; height: 100%; object-fit: cover; object-position: 80% 50%; display: block; }
.hero-copy { position: relative; max-width: var(--wrap); margin: 0 auto; padding: 26px var(--gut) 34px; background: var(--stone); }
.eyebrow { font: 400 .78rem/1.3 var(--mono); letter-spacing: .14em; text-transform: uppercase; color: var(--cobalt); margin: 0 0 14px; }
.hero h1 { margin: 0; font-weight: 400; letter-spacing: -.015em; }
.h1-a { display: block; font: 400 clamp(3.2rem, 11vw, 6.6rem)/.9 var(--serif); }
.h1-b { display: block; font: 400 clamp(1.7rem, 4.6vw, 2.7rem)/1.06 var(--serif); margin-top: 12px; color: var(--ink); }
.dek { font-size: clamp(1.05rem, 2.2vw, 1.22rem); line-height: 1.55; max-width: 34em; margin: 20px 0 10px; color: #262c3b; }
.byline { font-size: .9rem; color: var(--meta); margin: 0 0 24px; max-width: 46em; }
.actions { display: flex; flex-wrap: wrap; gap: 12px; }
.btn { display: inline-flex; flex-direction: column; gap: 2px; padding: 13px 20px 12px; border-radius: 14px; text-decoration: none; color: var(--ink); background: rgba(251, 249, 245, .9); border: 1px solid var(--line-2); box-shadow: var(--shadow); transition: transform .3s var(--ease), box-shadow .3s var(--ease); min-height: 44px; }
.btn span:first-child { font-weight: 600; }
.btn-meta { font: 400 .74rem/1.3 var(--mono); color: var(--meta); }
.btn.primary { background: var(--cobalt); color: #fff; border-color: var(--cobalt); }
.btn.primary .btn-meta { color: #DCE3FF; }
.btn:hover { transform: translateY(-2px); }
@media (min-width: 900px) {
  .hero { min-height: min(760px, 86vh); }
  .hero-art { position: absolute; inset: 0; aspect-ratio: auto; }
  .hero-art::after { content: ""; position: absolute; inset: 0; background: linear-gradient(90deg, rgba(242, 238, 232, .96) 0%, rgba(242, 238, 232, .86) 34%, rgba(242, 238, 232, .2) 58%, rgba(242, 238, 232, 0) 70%); }
  .hero-copy { background: none; padding: clamp(70px, 11vh, 120px) var(--gut) 80px; }
  .hero-copy > * { max-width: 620px; }
}

/* status + four questions */
.status { background: #FDF8F3; border-block: 1px solid rgba(200, 100, 59, .35); }
.status-in { max-width: var(--wrap); margin: 0 auto; padding: 16px var(--gut); display: flex; gap: 14px; align-items: flex-start; }
.status-in svg { width: 26px; height: 26px; flex: none; margin-top: 2px; }
.status-in p { margin: 0; }
.status-in strong { color: var(--terra-t); }
.four { max-width: var(--wrap); margin: 0 auto; padding: 34px var(--gut) 10px; }
.four-list { list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 14px; }
.q4 { position: relative; background: var(--paper); border: 1px solid var(--line); border-radius: 18px; padding: 18px 18px 18px 22px; box-shadow: var(--shadow); }
.q4::before { content: ""; position: absolute; left: 0; top: 18px; bottom: 18px; width: 3px; border-radius: 3px; background: var(--cobalt); }
.q4.int::before { background: var(--ink); } .q4.act::before { background: var(--terra); } .q4.chk::before { background: var(--aqua-t); }
.q4 .n { font: 400 .74rem var(--mono); color: var(--cobalt); letter-spacing: .1em; }
.q4 .q { display: block; margin: 6px 0 6px; line-height: 1.15; }
.q4 .d { font-size: .92rem; color: var(--meta); line-height: 1.45; }
.q4.obs .q { font: 400 1.08rem var(--mono); }
.q4.int .q { font: 600 1.18rem var(--sans); }
.q4.act .q { font: 400 1.6rem var(--serif); color: var(--terra-t); }
.q4.chk .q { font: 600 1.18rem var(--sans); color: var(--aqua-t); }

/* layout */
.layout { max-width: var(--wrap); margin: 0 auto; padding: 24px var(--gut) 40px; display: grid; grid-template-columns: minmax(0, 1fr); gap: 48px; }
.toc { display: none; }
@media (min-width: 1080px) {
  .layout { grid-template-columns: 236px minmax(0, 1fr); }
  .toc { display: block; position: sticky; top: 84px; align-self: start; max-height: calc(100vh - 100px); overflow: auto; padding-top: 30px; }
  .toc-m { display: none; }
}
.toc-h { font: 400 .72rem var(--mono); letter-spacing: .14em; text-transform: uppercase; color: var(--meta); margin: 0 0 10px; }
.toc ol, .toc-m ol { list-style: none; margin: 0; padding: 0; }
.toc li a, .toc-m li a { display: grid; grid-template-columns: 28px 1fr; gap: 4px; padding: 7px 8px; color: var(--ink); text-decoration: none; font-size: .9rem; line-height: 1.3; border-radius: 8px; border-left: 2px solid transparent; }
.toc li a:hover { background: rgba(35, 70, 216, .07); }
.toc li a[aria-current="true"] { background: var(--paper); border-left-color: var(--cobalt); box-shadow: var(--shadow); }
.tn { font: 400 .72rem/1.6 var(--mono); color: var(--cobalt); }
.toc-cta { display: grid; gap: 8px; margin-top: 18px; }
.mini { display: block; text-align: center; padding: 10px 12px; border-radius: 10px; border: 1px solid var(--line-2); color: var(--ink); text-decoration: none; font-weight: 600; font-size: .9rem; background: var(--paper); }
.mini:first-child { background: var(--ink); color: var(--stone); border-color: var(--ink); }
.toc-m { margin: 0 0 24px; background: var(--paper); border: 1px solid var(--line); border-radius: 14px; padding: 4px 8px; }
.toc-m summary { cursor: pointer; padding: 12px 8px; font-weight: 600; min-height: 44px; }

/* paper typography */
.paper { min-width: 0; max-width: 760px; }
.paper:focus { outline: none; }
.paper p { margin: 0 0 1.05em; }
.abstract h2, .sec > h2 { font-weight: 400; }
.abstract { padding-top: 26px; }
.abstract h2 { font: 400 2.4rem/1 var(--serif); margin: 0 0 14px; }
.abstract > p { font-size: 1.14rem; line-height: 1.62; }
.front-notes { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 18px; margin: 26px 0 0; padding-top: 20px; border-top: 1px solid var(--line-2); }
.front-notes p { font-size: .92rem; color: #2a3040; margin: 0; }
.front-notes .k { display: block; font: 400 .72rem var(--mono); letter-spacing: .14em; text-transform: uppercase; color: var(--meta); margin-bottom: 6px; }
.sec { margin-top: 72px; }
.sec > h2 { position: relative; display: grid; grid-template-columns: auto 1fr; gap: 18px; align-items: end; margin: 0 0 26px; padding-bottom: 14px; }
.sec > h2::after { content: ""; position: absolute; left: 0; right: 0; bottom: 0; height: 2px; border-radius: 2px; background: var(--spectral); }
.sn { font: 400 clamp(3rem, 7vw, 4.4rem)/.8 var(--serif); color: var(--cobalt); }
.st { font: 400 clamp(1.9rem, 4.4vw, 2.7rem)/1.02 var(--serif); letter-spacing: -.01em; }
h3 { font: 600 1.25rem/1.3 var(--sans); margin: 40px 0 12px; display: flex; gap: 12px; align-items: baseline; }
h3 .hn { font: 400 .82rem var(--mono); color: var(--cobalt); }
.kv-tag { display: inline-block; font: 400 .68rem/1 var(--mono); letter-spacing: .12em; text-transform: uppercase; padding: 5px 9px 4px; border-radius: 99px; margin-right: 8px; vertical-align: 2px; border: 1px solid currentColor; }
.kv-design .kv-tag { color: var(--cobalt); }
.kv-research .kv-tag { color: var(--aqua-t); }
.kv-limit .kv-tag { color: var(--terra-t); }
.kv-sim .kv-tag { color: var(--meta); }
.kv-limit { border-left: 3px solid var(--terra); padding-left: 16px; }
.kv-sim { background: var(--paper); border: 1px solid var(--line); padding: 16px 18px; border-radius: 14px; }
.cite { font: 400 .76rem var(--mono); color: var(--meta); white-space: nowrap; }
.cite a { text-decoration: none; }
.paper ul, .paper ol { padding-left: 1.3em; margin: 0 0 1.1em; }
.paper li { margin: 0 0 .5em; }
.paper li::marker { color: var(--cobalt); }
.tbl { overflow-x: auto; margin: 6px 0 24px; border-radius: 14px; border: 1px solid var(--line); background: var(--paper); }
table { width: 100%; border-collapse: collapse; font-size: .92rem; line-height: 1.45; }
th { font: 400 .7rem/1.3 var(--mono); letter-spacing: .1em; text-transform: uppercase; color: var(--meta); text-align: left; padding: 12px 14px 10px; border-bottom: 1px solid var(--ink); }
td { padding: 11px 14px; border-top: 1px solid var(--line); vertical-align: top; }
table.t-heron td:nth-child(2), table.t-heron td:nth-child(3) { font: 400 1rem var(--mono); }
table.t-heron td:nth-child(3) { color: var(--cobalt); }
table.t-heron td:first-child { font: 400 .9rem var(--mono); white-space: nowrap; }
table.t-page td:first-child { font-weight: 600; }

/* pull quotes */
.pq { margin: 34px 0; padding: 18px 0 0; position: relative; }
.pq::before { content: ""; position: absolute; left: 0; top: 0; width: 48px; height: 2px; background: var(--spectral); }
.pq p { font: 400 clamp(1.6rem, 3.6vw, 2.15rem)/1.12 var(--serif); margin: 0 !important; letter-spacing: -.005em; }
.pq p::before { content: "\201C"; color: var(--cobalt); }
.pq p::after { content: "\201D"; color: var(--cobalt); }
.pq .src { display: block; font: 400 .72rem var(--mono); letter-spacing: .12em; text-transform: uppercase; color: var(--meta); margin-top: 10px; }

/* figures */
.fig { margin: 36px 0 40px; }
.fig-frame { border-radius: 22px; box-shadow: var(--shadow); background: var(--stone); overflow: hidden; }
.fig-svg { display: block; width: 100%; height: auto; }
.fig-m, .fig-full { display: none; }
.fig-full { margin: 10px 0 0; font: 400 .8rem/1.4 var(--mono); }
.fig-full a { color: var(--cobalt); text-underline-offset: 3px; }
figcaption { margin-top: 14px; display: grid; grid-template-columns: auto 1fr; gap: 16px; }
.fn { font: 400 .74rem/1.9 var(--mono); letter-spacing: .12em; text-transform: uppercase; color: var(--cobalt); white-space: nowrap; }
.fc { font: 400 1.35rem/1.25 var(--serif); }
.fs { display: block; font: 400 .86rem/1.5 var(--sans); color: var(--meta); margin-top: 6px; }
@media (min-width: 1280px) { .fig { margin-right: -100px; } }
/* phones get the portrait version of each figure (labels about 11 px at a 354 px column) and a link to the full-size SVG */
@media (max-width: 680px) { figcaption { grid-template-columns: 1fr; gap: 4px; } .fig-d { display: none; } .fig-m, .fig-full { display: block; } }

.plate-art { margin: 0 0 30px; border-radius: 18px; overflow: hidden; aspect-ratio: 1400 / 350; box-shadow: var(--shadow); }
.plate-art img { width: 100%; height: 100%; object-fit: cover; display: block; }
#s6 .plate-art { aspect-ratio: 1400 / 380; }

/* references + evidence */
.refs .lead, .appx .lead { color: #2a3040; }
.refs-cols { font-size: .9rem; line-height: 1.5; }
.refs .ref { padding-left: 1.4em; text-indent: -1.4em; margin: 0 0 .9em; }
.refs .url { font: 400 .78rem var(--mono); }
.refs .note { font-size: .9rem; color: #2a3040; }
.appx .tbl { border-radius: 16px; }
table.ev { font-size: .88rem; }
.ev tr.grp th { font: 400 .72rem var(--mono); letter-spacing: .14em; color: var(--cobalt); background: var(--stone); padding: 16px 14px 10px; border-bottom: 1px solid var(--cobalt); }
.ev td.id { font: 400 .82rem var(--mono); color: var(--cobalt); white-space: nowrap; }
.ev td.src { min-width: 220px; }
.ev td.src b { font-weight: 600; }
.ev .loc { display: block; font: 400 .76rem/1.4 var(--mono); color: var(--meta); margin-top: 4px; }
.ev td.src a { display: block; font: 400 .74rem/1.4 var(--mono); margin-top: 4px; }
.ev .claim { display: block; color: #2a3040; margin-bottom: 6px; }
.ev q { display: block; font: 400 1.12rem/1.3 var(--serif); }
.ev tr:target td { background: #FFF6D8; }
@media (max-width: 760px) {
  table.ev thead { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); }
  table.ev, table.ev tbody, table.ev tr, table.ev td, table.ev th { display: block; width: 100%; }
  table.ev tr { padding: 10px 0; border-top: 1px solid var(--line); }
  table.ev td { border: 0; padding: 4px 14px; }
}

/* CTA band */
.cta { max-width: var(--wrap); margin: 30px auto 0; padding: 0 var(--gut) 60px; display: grid; gap: 28px; align-items: center; }
.cta-art { border-radius: 24px; overflow: hidden; box-shadow: var(--shadow); aspect-ratio: 1100 / 733; }
.cta-art img { width: 100%; height: 100%; object-fit: cover; display: block; }
.cta h2 { font: 400 clamp(2rem, 4.6vw, 3rem)/1.02 var(--serif); margin: 0 0 14px; }
@media (min-width: 900px) { .cta { grid-template-columns: 1.1fr 1fr; } }

/* footer */
.foot { background: var(--ink); color: #E8EAF0; }
.foot-in { max-width: var(--wrap); margin: 0 auto; padding: 44px var(--gut) 56px; display: grid; gap: 30px; }
.foot h2 { font: 400 1.6rem var(--serif); margin: 0 0 10px; color: #fff; }
.foot ul { margin: 0; padding-left: 1.1em; }
.foot a { color: #B9C6FF; }
.foot .plate { font: 400 .74rem var(--mono); letter-spacing: .1em; color: #B4BDD0; }
.foot-meta p { margin: 0 0 8px; font-size: .92rem; }
@media (min-width: 900px) { .foot-in { grid-template-columns: 1.2fr 1fr; } }

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .btn { transition: none; }
  .btn:hover { transform: none; }
  .progress { display: none; }
}
@media print {
  .top, .progress, .toc, .toc-m, .cta, .skip { display: none !important; }
  body { background: #fff; }
}

/* numerals: decimals get normal tracking, lining tabular figures and room around the point (0.9 never reads 09) */
.num { font-variant-numeric: lining-nums tabular-nums; letter-spacing: .015em; white-space: nowrap; }
.num .dp { padding: 0 .07em; }
/* URLs: the scheme is one unit; breaks only where the build put <wbr> (after / . - _ ? & =, before %) */
a.url { word-break: normal; overflow-wrap: anywhere; hyphens: none; }
a.url .pfx { white-space: nowrap; }

/* below-the-fold rendering is deferred until it nears the viewport; the markup stays in the HTML for readers and crawlers */
.sec.refs, .sec.appx { content-visibility: auto; contain-intrinsic-size: auto 2400px; }
.sec.appx { contain-intrinsic-size: auto 16000px; }