/* USF-Audio Tutorial. The USF Audio site identity (paper tones, serif display, ink and vermilion)
   with the DSP 2027 Explorer structure: claim, setup, verdict chips, linked live plots, numbered argument. */
:root {
  --bg: #fbfaf7; --surface: #ffffff; --tint: #f3f1ec; --tint2: #ece9e2;
  --fg: #16191d; --fg2: #3a3f46; --muted: #62676f; --faint: #8b9097;
  --line: #e6e2da; --line2: #d6d1c6; --grid: #eeebe4;
  --accent: #c4512b;               /* vermilion: chapter rule, numbers */
  --emph: #23508a;                 /* navy: links, emphasis */
  --emph-tint: rgba(35, 80, 138, .10);
  --sig: #16191d;                  /* g */
  --fold: #2e7d6b;                 /* y, y_q */
  --rec: #2c5f9e;                  /* recovered */
  --clip: #b5473a;                 /* clipped / PCM */
  --res: #c08a2e;                  /* residue eps */
  --qn: #7d5fa6;                   /* quantization noise q */
  --good: #2e7d6b; --warn: #b07a12; --crit: #b5473a;
  --display: "Source Serif 4", "Iowan Old Style", Georgia, serif;
  --sans: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-padding-top: 76px; }
body { margin: 0; background: var(--bg); color: var(--fg); font: 15.5px/1.65 var(--sans); -webkit-font-smoothing: antialiased; }
a { color: var(--emph); text-underline-offset: 3px; text-decoration-thickness: 1px; }
a:hover { text-decoration-thickness: 2px; }
img { max-width: 100%; display: block; }
[hidden] { display: none !important; }
.mono { font-family: var(--mono); font-variant-numeric: tabular-nums; }
:focus-visible { outline: 2px solid var(--emph); outline-offset: 2px; border-radius: 4px; }

/* ---------- top bar with chapter navigation ---------- */
.tbar { position: sticky; top: 0; z-index: 40; background: rgba(251,250,247,.9); backdrop-filter: saturate(1.4) blur(12px); -webkit-backdrop-filter: saturate(1.4) blur(12px); border-bottom: 1px solid var(--line); }
.tbar .inner { max-width: 1200px; margin: 0 auto; padding: 0 max(18px, env(safe-area-inset-left)); height: 60px; display: flex; align-items: center; gap: 18px; }
.brand { display: flex; align-items: center; gap: 10px; text-decoration: none; color: var(--fg); white-space: nowrap; }
.brand-mark { width: 30px; height: 30px; border-radius: 8px; background: var(--fg); display: grid; place-items: center; }
.brand-mark svg { width: 19px; height: 19px; }
.brand b { font-weight: 650; font-size: 15px; letter-spacing: -.01em; }
.brand small { display: block; font-size: 11.5px; color: var(--muted); line-height: 1.1; }
.chapnav { margin-left: auto; display: flex; gap: 2px; align-items: center; }
.chapnav a { text-decoration: none; color: var(--muted); font-size: 13.5px; font-weight: 500; padding: 6px 10px; border-radius: 999px; white-space: nowrap; }
.chapnav a:hover { color: var(--fg); background: var(--tint); }
.chapnav a[aria-current="page"] { color: var(--surface); background: var(--fg); }
.chapnav .num { font-family: var(--mono); font-size: 11.5px; opacity: .75; margin-right: 4px; }
.menu-btn { display: none; margin-left: auto; font: 500 14px var(--sans); border: 1px solid var(--line2); background: transparent; border-radius: 999px; padding: 6px 14px; color: var(--fg); }
@media (max-width: 1080px) {
  .menu-btn { display: block; }
  .chapnav { display: none; position: absolute; left: 0; right: 0; top: 60px; flex-direction: column; align-items: stretch; background: var(--bg); border-bottom: 1px solid var(--line); padding: 8px 18px 14px; }
  .chapnav.is-open { display: flex; }
  .chapnav a { border-radius: 8px; padding: 10px 12px; font-size: 15px; }
}

/* ---------- page ---------- */
.wrap { max-width: 1200px; margin: 0 auto; padding: 0 max(18px, env(safe-area-inset-left)) 64px; display: grid; gap: 22px; }
.pagehead { display: grid; gap: 12px; padding-top: 38px; }
.eyebrow { font: 500 12px/1.4 var(--mono); letter-spacing: .08em; text-transform: uppercase; color: var(--accent); margin: 0; }
h1 { font: 400 clamp(32px, 4.6vw, 52px)/1.06 var(--display); letter-spacing: -.02em; margin: 0; padding-bottom: 14px; border-bottom: 1.5px solid var(--accent); text-wrap: balance; }
h1 em { font-style: italic; color: var(--accent); }
h2 { font: 400 25px/1.2 var(--display); letter-spacing: -.012em; margin: 0; text-wrap: balance; }
h3 { font: 650 15.5px/1.35 var(--sans); margin: 0; letter-spacing: -.005em; }
.lede { max-width: 78ch; margin: 0; color: var(--fg2); font-size: 17px; line-height: 1.62; }
.lede strong, .alert { color: var(--emph); font-weight: 600; }
.prose { max-width: 78ch; color: var(--fg2); }
.prose p { margin: 0 0 12px; }
.prose p:last-child { margin: 0; }
.section-title { display: grid; gap: 6px; margin-top: 18px; }
.section-title .k { font: 500 11.5px var(--mono); letter-spacing: .08em; text-transform: uppercase; color: var(--muted); }

.panel { background: var(--surface); border: 1px solid var(--line); border-radius: 14px; padding: 16px 18px; min-width: 0; }

/* controls */
.setup { display: grid; gap: 14px; }
.setup .lab { font-size: 13px; color: var(--fg2); }
.setup .group { display: grid; gap: 6px; min-width: 0; justify-items: start; }
.sliders { display: grid; grid-template-columns: repeat(auto-fit, minmax(210px, 1fr)); gap: 12px 26px; }
.ctl { display: grid; gap: 5px; min-width: 0; }
.ctl .row { display: flex; justify-content: space-between; align-items: baseline; gap: 8px; font-size: 13.5px; color: var(--fg2); }
.ctl output { font: 500 13px var(--mono); color: var(--fg); white-space: nowrap; font-variant-numeric: tabular-nums; }
input[type=range] { width: 100%; accent-color: var(--emph); margin: 0; }
button { font: 500 13.5px var(--sans); color: var(--fg); background: var(--surface); border: 1px solid var(--line2); border-radius: 999px; padding: 6px 13px; cursor: pointer; }
button:hover { border-color: var(--fg); }
.btnrow { display: flex; flex-wrap: wrap; gap: 8px; }
.btnrow button[aria-pressed="true"] { background: var(--fg); color: var(--surface); border-color: var(--fg); }
.seg { display: inline-flex; flex-wrap: wrap; border: 1px solid var(--line2); border-radius: 999px; padding: 3px; gap: 2px; background: var(--surface); }
.seg button { border: 0; padding: 5px 12px; color: var(--fg2); }
.seg button[aria-pressed="true"] { background: var(--fg); color: var(--surface); }
.play { display: inline-flex; align-items: center; gap: 8px; background: var(--fg); color: var(--surface); border-color: var(--fg); }
.play:hover { background: #000; }
.play svg { width: 13px; height: 13px; }

/* verdict chips */
.status { display: flex; flex-wrap: wrap; gap: 8px; }
.chip { display: inline-flex; align-items: center; gap: 8px; font-size: 13.5px; color: var(--fg); background: var(--surface); border: 1px solid var(--line); border-radius: 999px; padding: 4px 13px 4px 7px; }
.chip .ic { width: 20px; height: 20px; flex: none; border-radius: 50%; display: inline-grid; place-items: center; font: 600 11px/1 var(--mono); color: #fff; background: var(--faint); }
.chip.ok .ic { background: var(--good); } .chip.warn .ic { background: var(--warn); } .chip.crit .ic { background: var(--crit); }
.chip b { font-weight: 600; }

/* plots */
.plot { display: grid; gap: 8px; min-width: 0; }
.plot-head { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: baseline; gap: 6px 16px; }
.plot-head h2 { font-size: 21px; }
.plot-sub { font-size: 13.5px; color: var(--muted); margin: 0; max-width: 80ch; }
.legend { display: flex; flex-wrap: wrap; gap: 4px 14px; font-size: 12.5px; color: var(--fg2); }
.legend > span { display: inline-flex; align-items: center; gap: 6px; }
.sw { width: 16px; height: 10px; display: inline-block; flex: none; }
.svgwrap { position: relative; width: 100%; min-width: 0; }
.svgwrap svg { display: block; width: 100%; height: auto; overflow: visible; }
svg text { font: 11px var(--mono); fill: var(--muted); }
.tip { position: absolute; top: 6px; left: 0; z-index: 2; pointer-events: none; background: var(--fg); color: var(--surface); font: 12px/1.45 var(--mono); padding: 6px 9px; border-radius: 6px; white-space: nowrap; font-variant-numeric: tabular-nums; }

.duo { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: 18px; align-items: start; }
.duo-wide { display: grid; grid-template-columns: minmax(0, 7fr) minmax(0, 5fr); gap: 18px; align-items: start; }
@media (max-width: 920px) { .duo, .duo-wide { grid-template-columns: minmax(0, 1fr); } }
.stack { display: grid; gap: 14px; min-width: 0; }

/* numbered argument */
.steps { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 16px; }
.step { display: grid; gap: 9px; align-content: start; }
.step .n { font: 400 34px/1 var(--display); color: var(--accent); }
.step p { margin: 0; color: var(--fg2); font-size: 14.5px; }
.step .live { font: 12.5px/1.5 var(--mono); color: var(--fg); background: var(--tint); border-radius: 8px; padding: 8px 10px; font-variant-numeric: tabular-nums; }
.math { overflow-x: auto; overflow-y: hidden; font-size: 14.5px; max-width: 100%; }
.katex { font-size: 1.06em; }
.katex-display { margin: .45em 0; }

/* boxed statements (theorems, definitions) */
.thm { border: 1px solid var(--line); border-left: 3px solid var(--emph); border-radius: 0 12px 12px 0; background: var(--surface); padding: 14px 18px; display: grid; gap: 8px; }
.thm .tt { font: 500 11.5px var(--mono); letter-spacing: .07em; text-transform: uppercase; color: var(--emph); }
.thm p { margin: 0; color: var(--fg2); }
.thm.key { border-left-color: var(--accent); } .thm.key .tt { color: var(--accent); }
.figure { margin: 0; display: grid; gap: 8px; }
.figure img { width: 100%; height: auto; border: 1px solid var(--line); border-radius: 10px; background: #fff; }
.figure figcaption { font-size: 13.5px; color: var(--muted); }

/* algorithm stepper */
.stepper { display: flex; flex-wrap: wrap; gap: 6px; align-items: center; }
.stepper .dot { font: 500 12.5px var(--sans); border: 1px solid var(--line2); background: var(--surface); color: var(--fg2); border-radius: 999px; padding: 5px 12px; }
.stepper .dot[aria-current="step"] { background: var(--accent); color: #fff; border-color: var(--accent); }
.stepper .dot.done { border-color: var(--fg); color: var(--fg); }

/* chapter cards (contents page) */
.cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 16px; }
.card { display: grid; gap: 10px; align-content: start; text-decoration: none; color: var(--fg); background: var(--surface); border: 1px solid var(--line); border-radius: 14px; padding: 18px; transition: border-color .2s, transform .2s; }
.card:hover { border-color: var(--fg); transform: translateY(-2px); }
.card .no { font: 400 34px/1 var(--display); color: var(--accent); }
.card h3 { font: 400 22px/1.2 var(--display); letter-spacing: -.01em; }
.card p { margin: 0; color: var(--muted); font-size: 14.5px; }
.card .glyph { height: 64px; border-radius: 9px; border: 1px solid var(--line); background: var(--bg); padding: 6px 8px; }
.card .glyph svg { width: 100%; height: 100%; }

.tbl { width: 100%; border-collapse: collapse; font-size: 14px; }
.tbl th, .tbl td { text-align: left; padding: 8px 10px; border-bottom: 1px solid var(--line); vertical-align: top; }
.tbl th { font: 500 11.5px var(--mono); letter-spacing: .06em; text-transform: uppercase; color: var(--muted); background: var(--tint); }

/* prev / next */
.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin-top: 10px; }
.pager a { display: grid; gap: 4px; text-decoration: none; color: var(--fg); background: var(--surface); border: 1px solid var(--line); border-radius: 14px; padding: 14px 18px; }
.pager a:hover { border-color: var(--fg); }
.pager .k { font: 500 11.5px var(--mono); letter-spacing: .07em; text-transform: uppercase; color: var(--muted); }
.pager b { font: 400 20px/1.25 var(--display); }
.pager .next { text-align: right; }
.paper-ref { font-size: 13.5px; color: var(--fg2); margin: 0; }
.paper-ref b { color: var(--fg); margin-right: 6px; }
.foot { font-size: 12.5px; color: var(--muted); max-width: 96ch; margin: 0; }

.sitefoot { border-top: 1px solid var(--line); }
.sitefoot .inner { max-width: 1200px; margin: 0 auto; padding: 18px max(18px, env(safe-area-inset-left)) 32px; font-size: 12.5px; color: var(--muted); line-height: 1.5; display: flex; flex-wrap: wrap; justify-content: space-between; gap: 10px 30px; }
.sitefoot b { color: var(--fg2); }
@media (prefers-reduced-motion: reduce) { * { transition: none !important; animation: none !important; scroll-behavior: auto !important; } }
@media (max-width: 600px) { .pager { grid-template-columns: 1fr; } .pager .next { text-align: left; } h1 { font-size: 32px; } }
/* narrow screens: wide formulas and tables scroll inside their own box, never the page */
.thm, .panel { min-width: 0; }
.thm .math, .step .math, .prose .math { overflow-x: auto; overflow-y: hidden; }
.tblwrap { overflow-x: auto; }
body { overflow-x: clip; }