/* ==========================================================================
   MSc lecture site - shared stylesheet
   Two course themes are selected with  <body data-course="om|qc">
   ========================================================================== */

:root{
  --ink:#16202b;
  --body:#33414f;
  --muted:#697a8a;
  --line:#dfe6ee;
  --bg:#eef3f8;
  --surface:#ffffff;
  --bg-soft:#f5f8fb;
  --bg-code:#0f1a25;
  --radius:14px;
  --maxw:1140px;
  --shadow:0 1px 2px rgba(16,32,48,.05),0 8px 28px rgba(16,32,48,.07);
  --font:'Segoe UI',Inter,system-ui,-apple-system,'Helvetica Neue',Arial,sans-serif;
  --mono:'Cascadia Mono',Consolas,'SF Mono',Menlo,monospace;
  --brand:#123a5e; --brand-2:#1f5c86; --accent:#de8a2a; --accent-2:#17788a;
  --tint:#eaf1f7; --tint-2:#fbf0de;
}
body[data-course="om"]{
  --brand:#123a5e; --brand-2:#1f5c86; --accent:#de8a2a; --accent-2:#17788a;
  --tint:#e3edf6; --tint-2:#fbf0de;
  --bg:#eef3f8; --bg-soft:#f7fafc;
}
body[data-course="qc"]{
  --brand:#241b4a; --brand-2:#3d2f7a; --accent:#6e4fd0; --accent-2:#0f9bb0;
  --tint:#e8e3f6; --tint-2:#dff1f5;
  --bg:#f2effa; --bg-soft:#faf9fd;
}

*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth;scroll-padding-top:84px}
body{font-family:var(--font);color:var(--body);background:var(--bg);
     line-height:1.65;font-size:17px;-webkit-font-smoothing:antialiased}
img{max-width:100%;height:auto}
a{color:var(--brand-2);text-decoration:none}
a:hover{text-decoration:underline}

/* ------------------------------------------------------------ top bar --- */
.topbar{position:sticky;top:0;z-index:50;background:color-mix(in srgb,
  var(--bg) 86%, #fff);
  backdrop-filter:saturate(180%) blur(12px);border-bottom:1px solid var(--line)}
.topbar .in{max-width:var(--maxw);margin:0 auto;padding:0 22px;height:62px;
  display:flex;align-items:center;gap:18px}
.brand{display:flex;align-items:center;gap:11px;font-weight:700;
  color:var(--brand);font-size:16.5px;white-space:nowrap}
.brand .dot{width:13px;height:13px;border-radius:4px;background:var(--accent);
  flex:0 0 auto}
.topnav{margin-left:auto;display:flex;gap:20px;font-size:15px;flex-wrap:wrap}
.topnav a{color:var(--muted);font-weight:500}
.topnav a:hover,.topnav a.on{color:var(--brand);text-decoration:none}
.progress{position:absolute;left:0;bottom:-1px;height:3px;width:0;
  background:var(--accent);transition:width .15s linear}

/* --------------------------------------------------------------- hero --- */
.hero{background:var(--brand);color:#fff;padding:86px 22px 76px;
  position:relative;overflow:hidden}
.hero .in{max-width:var(--maxw);margin:0 auto;position:relative;z-index:2}
.hero .kick{font-size:13.5px;letter-spacing:3.4px;text-transform:uppercase;
  color:var(--accent);font-weight:700}
.hero h1{font-size:clamp(34px,5.2vw,60px);line-height:1.08;margin-top:18px;
  font-weight:800;letter-spacing:-1.1px;color:#fff}
.hero p.lead{margin-top:20px;font-size:clamp(17px,2vw,21px);color:#c9d3e2;
  max-width:760px}
.hero .cta{margin-top:32px;display:flex;gap:13px;flex-wrap:wrap}
.btn{display:inline-flex;align-items:center;gap:9px;padding:12px 22px;
  border-radius:10px;font-weight:600;font-size:15.5px;border:1.5px solid
  transparent;transition:transform .15s ease,box-shadow .15s ease}
.btn:hover{text-decoration:none;transform:translateY(-1px)}
.btn-p{background:var(--accent);color:#15202b}
.btn-g{border-color:rgba(255,255,255,.34);color:#fff}
.btn-g:hover{background:rgba(255,255,255,.1)}
.hero .orb{position:absolute;border-radius:50%;filter:blur(3px);opacity:.16;
  background:var(--accent);animation:float 16s ease-in-out infinite}
.hero .orb.a{width:340px;height:340px;right:-70px;top:-90px}
.hero .orb.b{width:220px;height:220px;right:190px;bottom:-110px;
  background:var(--accent-2);animation-delay:-6s}
@keyframes float{0%,100%{transform:translate3d(0,0,0)}
  50%{transform:translate3d(-22px,26px,0)}}

/* --------------------------------------------------------------- page --- */
.wrap{max-width:var(--maxw);margin:0 auto;padding:0 22px}
.layout{display:grid;grid-template-columns:238px minmax(0,1fr);gap:46px;
  align-items:start;padding:40px 0 90px}
@media(max-width:960px){.layout{grid-template-columns:1fr;gap:0}}

/* sidebar table of contents */
.toc{position:sticky;top:84px;font-size:14.5px;max-height:calc(100vh - 110px);
  overflow:auto;padding-right:8px}
.toc .lbl{font-size:11.5px;letter-spacing:2px;text-transform:uppercase;
  color:var(--muted);font-weight:700;margin-bottom:12px}
.toc a{display:block;padding:6px 0 6px 13px;color:var(--muted);
  border-left:2px solid var(--line);line-height:1.35}
.toc a:hover{color:var(--brand);text-decoration:none}
.toc a.on{color:var(--brand);border-left-color:var(--accent);font-weight:600}
@media(max-width:960px){.toc{display:none}}

/* --------------------------------------------------------- typography --- */
.lesson-head{padding:44px 0 8px}
.lesson-head .eyebrow{font-size:12.5px;letter-spacing:2.6px;
  text-transform:uppercase;color:var(--accent);font-weight:700}
.lesson-head h1{font-size:clamp(30px,4.4vw,44px);line-height:1.13;
  color:var(--ink);margin-top:12px;font-weight:800;letter-spacing:-.7px}
.lesson-head .sub{margin-top:12px;color:var(--muted);font-size:17px}

section{scroll-margin-top:84px;padding-top:26px}
h2{font-size:27px;color:var(--ink);font-weight:750;letter-spacing:-.35px;
   margin:34px 0 14px;line-height:1.25;padding-bottom:9px;
   border-bottom:2px solid var(--line);position:relative}
h2:after{content:'';position:absolute;left:0;bottom:-2px;width:58px;height:2px;
   background:var(--accent)}
h3{font-size:20.5px;color:var(--ink);font-weight:700;margin:26px 0 9px}
h4{font-size:17.5px;color:var(--brand-2);font-weight:700;margin:20px 0 6px}
p{margin:0 0 15px}
ul,ol{margin:0 0 16px 22px}
li{margin-bottom:8px}
strong{color:var(--ink);font-weight:660}
em{color:var(--ink)}
code{font-family:var(--mono);font-size:.92em;background:var(--tint);
  padding:2px 6px;border-radius:5px;color:var(--brand)}

/* callouts */
.note,.warn,.key{border-radius:12px;padding:16px 20px;margin:20px 0;
  border-left:5px solid;font-size:16.5px}
.note{background:var(--tint);border-color:var(--accent-2)}
.warn{background:#fdf1ee;border-color:#c0392b}
.key{background:var(--tint-2);border-color:var(--accent)}
.note b,.warn b,.key b{display:block;margin-bottom:4px;color:var(--ink);
  font-size:15px;letter-spacing:.2px;text-transform:uppercase;
  font-weight:700;opacity:.75}

/* definition block */
.def{background:#fff;border:1.5px solid var(--line);border-radius:12px;
  padding:18px 22px;margin:20px 0;box-shadow:var(--shadow)}
.def .dt{font-size:12.5px;letter-spacing:2px;text-transform:uppercase;
  color:var(--accent);font-weight:700;margin-bottom:6px}
.def .dn{font-weight:750;color:var(--ink);font-size:18.5px;margin-bottom:6px}

/* equations */
.eq{background:var(--surface);border:1px solid var(--line);
  border-left:5px solid var(--accent);
  border-radius:10px;padding:18px 24px;margin:18px 0;text-align:center;
  font-size:20px;color:var(--brand);font-weight:600;line-height:1.85;
  overflow-x:auto}
.eq .small{font-size:16px;font-weight:500;color:var(--muted);display:block;
  margin-top:6px}
.eqi{font-weight:650;color:var(--brand);white-space:nowrap}

/* tables */
.tbl{width:100%;border-collapse:collapse;margin:20px 0;font-size:16px;
  box-shadow:var(--shadow);border-radius:11px;overflow:hidden}
.tbl th{background:var(--brand);color:#fff;text-align:left;padding:11px 15px;
  font-weight:650;font-size:15.5px}
.tbl td{padding:10px 15px;border-bottom:1px solid var(--line);
  background:#fff;vertical-align:top}
.tbl tr:nth-child(even) td{background:var(--bg-soft)}
.tbl tr.hl td{background:var(--tint-2);font-weight:650;color:var(--ink)}
.scroll-x{overflow-x:auto}

/* worked problem */
.prob{border:1.5px solid var(--line);border-radius:14px;margin:26px 0;
  overflow:hidden;box-shadow:var(--shadow)}
.prob .ph{background:var(--brand);color:#fff;padding:12px 20px;
  font-weight:700;font-size:17px;display:flex;align-items:center;gap:11px}
.prob .ph .n{background:var(--accent);color:#15202b;border-radius:7px;
  padding:1px 10px;font-size:14px;font-weight:800}
.prob .stmt{background:var(--bg-soft);padding:15px 22px;font-style:italic;
  color:#2b3742;
  border-bottom:1px solid var(--line)}
.prob .body{padding:18px 22px}
.prob .step{margin-bottom:16px}
.prob .step .sh{color:var(--accent-2);font-weight:700;margin-bottom:5px}
.prob .ans{background:var(--tint-2);border:2px solid var(--accent);
  border-radius:10px;padding:12px 18px;text-align:center;font-weight:750;
  font-size:19px;color:var(--brand);margin-top:6px}

/* plain-English block */
.plain{background:linear-gradient(180deg,var(--tint-2),var(--surface));
  border:1.5px solid var(--accent);border-radius:14px;padding:22px 26px;
  margin:26px 0}
.plain .tag{display:inline-block;background:var(--accent);color:#15202b;
  font-size:11.5px;letter-spacing:2px;text-transform:uppercase;font-weight:800;
  padding:3px 11px;border-radius:20px;margin-bottom:11px}
.plain p:last-child{margin-bottom:0}

/* application cards */
.apps{display:grid;grid-template-columns:repeat(auto-fit,minmax(255px,1fr));
  gap:15px;margin:20px 0}
.app{border:1.5px solid var(--line);border-left:5px solid var(--accent-2);
  border-radius:12px;padding:15px 18px;background:#fff;box-shadow:var(--shadow)}
.app h5{font-size:16.5px;color:var(--ink);font-weight:700;margin-bottom:5px}
.app p{font-size:15.5px;margin:0;color:var(--body)}

/* ------------------------------------------------------- visualisation --- */
.viz{background:#fff;border:1.5px solid var(--line);border-radius:14px;
  margin:26px 0;overflow:hidden;box-shadow:var(--shadow)}
.viz .vh{padding:12px 20px;border-bottom:1px solid var(--line);
  background:var(--bg-soft);display:flex;align-items:center;gap:12px;
  flex-wrap:wrap}
.viz{background:var(--surface)}
.viz .vh .vt{font-weight:700;color:var(--ink);font-size:16px}
.viz .vh .vs{color:var(--muted);font-size:14.5px}
.viz .vbody{padding:18px 20px}
.viz svg{display:block;width:100%;height:auto;overflow:visible}
.ctl{display:flex;gap:16px;align-items:center;flex-wrap:wrap;
  padding:12px 20px;border-top:1px solid var(--line);background:var(--bg-soft)}
.ctl label{font-size:14.5px;color:var(--muted);display:flex;align-items:center;
  gap:9px;font-weight:600}
.ctl input[type=range]{width:158px;accent-color:var(--accent)}
.ctl .val{font-family:var(--mono);color:var(--brand);font-weight:700;
  min-width:56px;display:inline-block;font-size:14px}
.ctl button{background:#fff;border:1.5px solid var(--line);border-radius:9px;
  padding:6px 14px;font-family:var(--font);font-size:14.5px;font-weight:650;
  color:var(--brand);cursor:pointer;transition:.14s}
.ctl button:hover{border-color:var(--accent);color:var(--ink)}
.ctl button.pri{background:var(--accent);border-color:var(--accent);
  color:#15202b}
.ctl .gate{min-width:42px;text-align:center;font-family:var(--mono);
  font-weight:800}
.readout{font-family:var(--mono);font-size:14px;color:var(--muted);
  padding:0 20px 14px}
.readout b{color:var(--brand)}
/* the two ways of taking the same material: read it, or present it */
.viewsw{display:inline-flex;align-items:stretch;border:1.5px solid var(--line);
  border-radius:9px;overflow:hidden;background:var(--surface);margin-left:4px}
.viewsw a,.viewsw span{display:flex;align-items:center;gap:6px;
  padding:6px 13px;font-size:14.5px;font-weight:600;color:var(--muted);
  text-decoration:none;line-height:1.2;white-space:nowrap}
.viewsw a:hover{background:var(--tint);color:var(--brand);text-decoration:none}
.viewsw [aria-current]{background:var(--brand);color:#fff;cursor:default}
.viewsw a+a,.viewsw span+a,.viewsw a+span{border-left:1.5px solid var(--line)}
/* On a phone the bar has room for the title and the view switch, and that
   is all: the secondary links go, since the title already returns to the
   contents. Wrapping instead would spill out of the bar's fixed height. */
@media (max-width:700px){
  .topbar .in{padding:0 14px;gap:10px}
  .brand{min-width:0;overflow:hidden;text-overflow:ellipsis;font-size:15px}
  .topnav{flex-wrap:nowrap;gap:0}
  .topnav>a{display:none}
  .viewsw{margin-left:0}
  .viewsw a,.viewsw span{padding:6px 11px;font-size:13.5px}
}
/* A grid item will not shrink below its widest child, so a wide table used to
   push the whole column past the screen and the page scrolled sideways. Let
   the column shrink, and let the table itself be the thing that scrolls. */
@media (max-width:760px){
  .layout>*{min-width:0}
  main table,.wrap table{display:block;width:max-content;max-width:100%;
    overflow-x:auto;-webkit-overflow-scrolling:touch}
}
/* Touch needs a bigger target than a mouse does. Keyed on the pointer rather
   than the width, so a small window on a desktop is left alone. */
@media (pointer:coarse){
  .viewsw a,.viewsw span{min-height:40px}
  .viz button,.viz select,.viz input[type=button]{min-height:38px;
    padding-top:8px;padding-bottom:8px}
  .viz input[type=range]{height:32px}
}
@media (max-width:380px){
  .brand span:not(.dot){display:none}
  .viewsw a,.viewsw span{padding:6px 9px;font-size:13px}
}

/* raised exponents that do not open up the line they sit in */
sup{font-size:.68em;line-height:0;vertical-align:.5em}
sub{font-size:.68em;line-height:0;vertical-align:-.22em}
.figcap{font-size:14.5px;color:var(--muted);font-style:italic;
  padding:0 20px 14px;text-align:center}

/* svg helpers */
.axis{stroke:#b9c6d3;stroke-width:1.4}
.grid{stroke:#e8eef4;stroke-width:1}
.lbl{font-size:13px;fill:var(--muted);font-family:var(--font)}
.lbl-b{font-size:13.5px;fill:var(--ink);font-weight:700;font-family:var(--font)}
.dash{stroke-dasharray:6 5}
.flow-node{transition:.3s}
.pulse{animation:pulse 2.4s ease-in-out infinite}
@keyframes pulse{0%,100%{opacity:.35}50%{opacity:1}}
.draw{stroke-dasharray:var(--len,1400);stroke-dashoffset:var(--len,1400);
  animation:draw 2.2s ease forwards}
@keyframes draw{to{stroke-dashoffset:0}}

/* ------------------------------------------------------------- footer --- */
.pager{display:flex;justify-content:space-between;gap:14px;margin:52px 0 0;
  padding-top:26px;border-top:1px solid var(--line);flex-wrap:wrap}
.pager a{display:block;border:1.5px solid var(--line);border-radius:12px;
  padding:13px 19px;max-width:46%;background:#fff}
.pager a:hover{border-color:var(--accent);text-decoration:none}
.pager .d{font-size:12px;letter-spacing:1.6px;text-transform:uppercase;
  color:var(--muted);font-weight:700}
.pager .t{color:var(--ink);font-weight:650;margin-top:3px}
.pager a.next{margin-left:auto;text-align:right}
footer.site{background:var(--brand);color:#a9b7ca;padding:38px 22px;
  font-size:14.5px;margin-top:0}
footer.site .in{max-width:var(--maxw);margin:0 auto;display:flex;
  justify-content:space-between;gap:18px;flex-wrap:wrap}
footer.site a{color:#dbe4ef}
/* the author's name, small enough to stay out of the way */
footer.site .sig{max-width:var(--maxw);margin:14px auto 0;text-align:left;
  font-size:9px;letter-spacing:.4px;color:#8a9bb0;opacity:.85}

/* --------------------------------------------------------- index page --- */
.courses{display:grid;grid-template-columns:repeat(auto-fit,minmax(320px,1fr));
  gap:24px;margin:36px 0 10px}
.course{border:1.5px solid var(--line);border-radius:18px;overflow:hidden;
  background:#fff;box-shadow:var(--shadow);transition:.2s}
.course:hover{transform:translateY(-3px);box-shadow:0 14px 40px rgba(16,32,48,.12)}
.course .ch{padding:24px 26px;color:#fff}
.course.om .ch{background:linear-gradient(135deg,#123a5e,#1f5c86)}
.course.qc .ch{background:linear-gradient(135deg,#241b4a,#3d2f7a)}
.course .ch .code{font-size:12.5px;letter-spacing:2.6px;font-weight:700;
  opacity:.8}
.course .ch h3{color:#fff;font-size:24px;margin:8px 0 0;line-height:1.2}
.course .ch p{margin:10px 0 0;font-size:15.5px;opacity:.86}
.course .cb{padding:20px 26px 26px}
.lessons{list-style:none;margin:0}
.lessons li{margin:0;border-bottom:1px solid var(--line)}
.lessons li:last-child{border-bottom:none}
.lessons a{display:flex;gap:13px;align-items:baseline;padding:11px 2px;
  color:var(--body)}
.lessons a:hover{color:var(--brand);text-decoration:none}
.lessons .num{font-family:var(--mono);font-size:13px;color:var(--accent);
  font-weight:800;min-width:34px}
.stats{display:grid;grid-template-columns:repeat(auto-fit,minmax(150px,1fr));
  gap:16px;margin:34px 0}
.stat{background:var(--surface);border-radius:13px;padding:19px 21px;
  border:1px solid var(--line);box-shadow:var(--shadow)}
.stat .n{font-size:31px;font-weight:800;color:var(--brand);line-height:1}
.stat .l{font-size:14px;color:var(--muted);margin-top:5px}

.reveal{opacity:0;transform:translateY(16px)}
.reveal.in{opacity:1;transform:none;transition:opacity .55s ease,transform .55s ease}
@media (prefers-reduced-motion:reduce){
  *{animation-duration:.001ms!important;transition-duration:.001ms!important}
  .reveal{opacity:1;transform:none}
}

/* ------------------------------------------------- present-mode link --- */
.topnav a.present{border:1.5px solid var(--accent);border-radius:8px;
  padding:5px 13px;color:var(--brand);font-weight:650}
.topnav a.present:hover{background:var(--accent);color:#15202b;
  text-decoration:none}