:root{
  --bg:#f7f6f2;
  --card:#ffffff;
  --ink:#26303b;
  --muted:#6b7785;
  --line:#e7e4dc;
  --accent:#2f8f7e;
  --accent-soft:#dcefe9;
  --warm:#e8804b;         /* current-state marker */
  --warm-soft:#fbe3d6;
  --blue:#3d6fb4;         /* transmission / EIR */
  --blue-soft:#dde7f3;
  --clin:#7b5bd6;         /* clinical incidence */
  --clin-soft:#e7e0f7;
  --danger:#d1495b;       /* rebound / dip below baseline */
  --danger-soft:#f6dbe0;
  --shadow:0 1px 2px rgba(20,30,40,.05),0 8px 24px rgba(20,30,40,.06);
  --radius:18px;
  --maxw:760px;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;
  background:var(--bg);color:var(--ink);line-height:1.65;-webkit-font-smoothing:antialiased}
.wrap{max-width:var(--maxw);margin:0 auto;padding:0 22px}
.wrapwide{max-width:1080px;margin:0 auto;padding:0 22px}
header.hero{text-align:center;padding:56px 22px 24px}
.hero-logo{display:block;width:72px;height:72px;margin:0 auto 20px}
.kicker{text-transform:uppercase;letter-spacing:.14em;font-size:13px;font-weight:700;color:var(--accent);margin-bottom:14px}
h1{font-size:clamp(27px,4.6vw,40px);line-height:1.12;margin:0 0 16px;font-weight:800;letter-spacing:-.02em}
.lede{font-size:18px;color:var(--muted);max-width:620px;margin:0 auto}
section{margin:30px 0}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  padding:28px 30px;box-shadow:var(--shadow);margin-bottom:24px}
h2{font-size:23px;margin:0 0 6px;font-weight:750;letter-spacing:-.01em;display:flex;align-items:center;gap:12px}
.num{flex:none;width:34px;height:34px;border-radius:50%;background:var(--accent-soft);color:var(--accent);
  display:grid;place-items:center;font-size:16px;font-weight:800}
h2 + .sub{color:var(--muted);margin:2px 0 18px 46px;font-size:16px}
h3{font-size:15px;font-weight:750;margin:22px 0 4px;letter-spacing:.01em;text-transform:uppercase;
  font-size:12.5px;letter-spacing:.08em;color:var(--accent)}
p{margin:13px 0}
.muted{color:var(--muted)}
.var{font-style:italic;font-family:Georgia,"Times New Roman",serif}
strong{font-weight:700}
canvas{width:100%;display:block}
.pill{display:inline-block;background:var(--accent-soft);color:var(--accent);
  padding:1px 9px;border-radius:999px;font-size:13px;font-weight:700;white-space:nowrap}
.pill.warm{background:var(--warm-soft);color:#c45a25}
.pill.blue{background:var(--blue-soft);color:#345f9c}

/* work-in-progress status badge (landing hero): a soft-warm pill with a live dot */
.wip-badge{display:inline-flex;align-items:center;gap:7px;margin:14px auto 20px;
  background:var(--warm-soft);color:#c45a25;border:1px solid #f3c9b3;
  padding:5px 13px 5px 11px;border-radius:999px;font-size:13px;font-weight:700;
  text-decoration:none;white-space:nowrap;transition:filter .15s}
.wip-badge:hover{filter:brightness(.97)}
.wip-badge .dot{width:8px;height:8px;border-radius:50%;background:var(--warm);flex:none;
  box-shadow:0 0 0 0 rgba(232,128,75,.55);animation:wipPulse 2.4s ease-out infinite}
@keyframes wipPulse{0%{box-shadow:0 0 0 0 rgba(232,128,75,.5)}
  70%{box-shadow:0 0 0 7px rgba(232,128,75,0)}100%{box-shadow:0 0 0 0 rgba(232,128,75,0)}}
@media (prefers-reduced-motion:reduce){.wip-badge .dot{animation:none}}

/* illustrative-only tag pinned to each explainer's interactive toy card */
.card.toy{position:relative}
.toy-tag{position:absolute;top:26px;right:28px;z-index:2;
  display:inline-flex;align-items:center;gap:6px;
  background:var(--warm-soft);color:#c45a25;border:1px solid #f3c9b3;
  padding:3px 11px;border-radius:999px;font-size:11.5px;font-weight:700;
  letter-spacing:.01em;white-space:nowrap}
.toy-tag::before{content:"";width:6px;height:6px;border-radius:50%;background:var(--warm);flex:none}
.card.toy > h2{padding-right:240px}
@media(max-width:640px){
  .toy-tag{position:static;margin:0 0 12px}
  .card.toy > h2{padding-right:0}
}

.eqline{font-family:Georgia,"Times New Roman",serif;font-size:16px;background:#f4f2ec;border:1px solid var(--line);
  border-radius:10px;padding:14px 16px;margin:16px 0;text-align:center}
.frac{display:inline-flex;flex-direction:column;align-items:center;vertical-align:middle;margin:0 5px}
.frac > span{display:block;padding:1px 10px}
.frac .den{border-top:2px solid var(--ink)}
sup{font-size:.7em}

/* ---- Ross–Macdonald formula (section 1) ---- */
.formula{background:linear-gradient(180deg,#fbfaf7,#f4f2ec);border:1px solid var(--line);border-radius:14px;
  padding:26px 20px;text-align:center;margin:18px 0 8px;font-size:22px}
.eq{display:inline-flex;align-items:center;gap:8px;font-family:Georgia,"Times New Roman",serif}
.r0{display:inline-block;position:relative}
.r0 sub{font-size:.6em;font-style:normal;line-height:0;position:relative;bottom:-.28em;margin-left:1px;
  font-family:-apple-system,"Segoe UI",Roboto,Arial,sans-serif}
.legend{display:grid;grid-template-columns:repeat(auto-fit,minmax(180px,1fr));gap:10px 24px;margin-top:20px;
  list-style:none;padding:0;font-size:15px}
.legend li{display:flex;gap:10px}
.legend .sym{font-family:Georgia,serif;font-style:italic;font-weight:700;color:var(--accent);min-width:24px}
.highlight-term{color:var(--warm);font-weight:700}
.hl-bite{color:var(--warm);font-weight:700}
.caption{font-size:13.5px;color:var(--muted);margin-top:14px}
.chartbox{float:right;width:330px;max-width:46%;margin:2px 0 10px 22px}
.chartbox .caption{margin-top:6px;font-size:12px}
@media(max-width:560px){.chartbox{float:none;width:100%;max-width:none;margin:10px 0}}
/* concept 2: text and the decay chart as two balanced columns, so a short body
   doesn't leave a tall gap beside the floated chart. Stacks below 760px, where a
   two-column split would leave the text column too narrow to read comfortably. */
.c2cols{display:grid;grid-template-columns:1fr 300px;gap:26px;align-items:center}
.c2cols .chartbox{float:none;width:auto;max-width:none;margin:0}
@media(max-width:760px){
  .c2cols{grid-template-columns:1fr;gap:4px}
  .c2cols .chartbox{max-width:420px;margin-top:8px}
}

/* ---- controls ---- */
.controls{display:grid;grid-template-columns:1fr 1fr;gap:16px;margin-bottom:4px}
@media(max-width:620px){.controls{grid-template-columns:1fr}}
.slider-block{border-radius:14px;padding:16px 20px}
.slider-block.eir{background:var(--blue-soft)}
.slider-block.cov{background:var(--accent-soft)}
.slider-top{display:flex;justify-content:space-between;align-items:baseline;margin-bottom:8px}
.slider-top .label{font-weight:700;font-size:15px}
.slider-top .val{font-size:26px;font-weight:800}
.slider-block.eir .val{color:var(--blue)}
.slider-block.cov .val{color:var(--accent)}
.slider-sub{font-size:12.5px;margin-top:6px}
input[type=range]{-webkit-appearance:none;appearance:none;width:100%;height:8px;border-radius:999px;outline:none;margin:4px 0}
input[type=range]::-webkit-slider-thumb{-webkit-appearance:none;appearance:none;width:24px;height:24px;border-radius:50%;
  background:#fff;cursor:pointer;box-shadow:0 2px 6px rgba(0,0,0,.18)}
input[type=range]::-moz-range-thumb{width:20px;height:20px;border-radius:50%;background:#fff;cursor:pointer}
input[type=range]:focus-visible{outline:2px solid var(--ink);outline-offset:4px}
#eir0{background:linear-gradient(90deg,var(--blue) 0%,var(--blue) var(--fill,0%),#c7d6ec var(--fill,0%),#c7d6ec 100%)}
#eir0::-webkit-slider-thumb{border:3px solid var(--blue)} #eir0::-moz-range-thumb{border:3px solid var(--blue)}
#use{background:linear-gradient(90deg,var(--accent) 0%,var(--accent) var(--fill,0%),#c7e0d8 var(--fill,0%),#c7e0d8 100%)}
#use::-webkit-slider-thumb{border:3px solid var(--accent)} #use::-moz-range-thumb{border:3px solid var(--accent)}

.readouts{display:grid;grid-template-columns:repeat(auto-fit,minmax(140px,1fr));gap:12px;margin:18px 0 4px}
.readout{background:var(--bg);border:1px solid var(--line);border-radius:12px;padding:12px 14px;text-align:center}
.readout .v{font-size:23px;font-weight:800;line-height:1.1}
.readout .l{font-size:12px;color:var(--muted);margin-top:3px}

.plots{display:grid;grid-template-columns:repeat(3,1fr);gap:16px 18px;margin-top:14px;align-items:start}
@media(max-width:860px){.plots{grid-template-columns:repeat(2,1fr);gap:22px}}
@media(max-width:520px){.plots{grid-template-columns:1fr}}
/* the coverage-cascade row has only two plots; centre it under the three-wide general row */
.plots.plots2{grid-template-columns:repeat(2,minmax(0,1fr));max-width:66%;margin-inline:auto}
@media(max-width:860px){.plots.plots2{max-width:none}}
@media(max-width:520px){.plots.plots2{grid-template-columns:1fr}}
/* heading above each plot group */
.panel-group-h{font-size:14px;font-weight:750;margin:24px 0 0}
.panel-group-h .muted{font-weight:400}
.panel{min-width:0}
.panel-h{font-size:14px;font-weight:750;margin:0 0 4px;display:flex;align-items:center;gap:8px}
.panel-h .step{flex:none;width:22px;height:22px;border-radius:50%;display:grid;place-items:center;
  font-size:12px;font-weight:800;color:#fff}
.pcap{font-size:12px;color:var(--muted);margin:8px 0 0;line-height:1.5}
.note{font-size:13.5px;color:var(--muted);border-left:3px solid var(--line);padding:6px 0 6px 14px;margin:18px 0;line-height:1.6}
.note p{margin:8px 0}
.note ul{margin:8px 0;padding-left:18px}
.note ol.refs{margin:8px 0 0;padding-left:22px}
.note ol.refs li{margin:0 0 7px}
.note li{margin:6px 0}
.note strong{color:var(--ink)}
footer{text-align:center;padding:24px 22px 60px;color:var(--muted);font-size:13.5px}
a{color:var(--accent)}
sup.cite{line-height:0}
sup.cite a{text-decoration:none;font-weight:700;padding:0 1px}

/* ============================================================
   Hub landing page (index.html)
   ============================================================ */
.lessons{display:grid;grid-template-columns:repeat(2,1fr);gap:20px;margin-top:8px}
@media(max-width:720px){.lessons{grid-template-columns:1fr}}
a.lesson-card{display:flex;flex-direction:column;text-decoration:none;color:inherit;
  background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  padding:24px 26px;box-shadow:var(--shadow);transition:transform .12s ease,box-shadow .12s ease}
a.lesson-card:hover{transform:translateY(-3px);box-shadow:0 2px 4px rgba(20,30,40,.06),0 14px 34px rgba(20,30,40,.10)}
.lesson-card .lc-num{width:34px;height:34px;border-radius:50%;background:var(--accent-soft);color:var(--accent);
  display:grid;place-items:center;font-size:16px;font-weight:800;margin-bottom:14px}
.lesson-card h2{font-size:20px;display:block;margin:0 0 8px}
.lesson-card p{font-size:14.5px;color:var(--muted);margin:0 0 16px}
.lesson-card .go{margin-top:auto;font-weight:700;color:var(--accent);font-size:14px}
.lesson-card.soon{opacity:.7;cursor:default;box-shadow:none;border-style:dashed}
.lesson-card.soon:hover{transform:none;box-shadow:none}
.lesson-card.soon .lc-num{background:var(--line);color:var(--muted)}
.lesson-card.warm .lc-num{background:var(--warm-soft);color:#c45a25}
.lesson-card.warm .go{color:var(--warm)}
.lesson-card.blue .lc-num{background:var(--blue-soft);color:var(--blue)}
.lesson-card.blue .go{color:var(--blue)}
.lesson-card.clin .lc-num{background:var(--clin-soft);color:var(--clin)}
.lesson-card.clin .go{color:var(--clin)}
.crumb{max-width:1080px;margin:0 auto;padding:18px 22px 0}
.crumb a{font-weight:700;font-size:14px;text-decoration:none}
.lessons-h{font-size:18px;margin:6px 0 12px;color:var(--ink)}

/* Feynman-technique flow schematic */
.feynman{display:flex;align-items:stretch;gap:10px;margin-top:18px}
.fstep{flex:1 1 0;min-width:0;display:flex;gap:11px;align-items:flex-start;
  background:var(--bg);border:1px solid var(--line);border-radius:12px;padding:12px 14px}
.fstep b{display:block;font-size:14px;line-height:1.25}
.fstep div span{display:block;font-size:12px;color:var(--muted);margin-top:2px;line-height:1.35}
.fstep .fnum{flex:none;width:25px;height:25px;border-radius:50%;display:grid;place-items:center;
  line-height:1;font-weight:800;font-size:13px;color:#fff;margin-top:1px}
.farrow{flex:none;display:flex;align-items:center;color:var(--muted);font-size:20px;font-weight:700}
@media(max-width:760px){
  .feynman{flex-direction:column;align-items:stretch}
  .fstep{flex:0 0 auto}
  .farrow{transform:rotate(90deg);align-self:center;margin:-2px 0}
}

/* ============================================================
   Rebounds lesson (rebounds.html)
   ============================================================ */
/* triangle diagram */
.triangle-wrap{margin:14px 0 4px}
.triangle-wrap svg{width:100%;height:auto;display:block;max-width:680px;margin:0 auto}
.tri-corner{cursor:pointer;outline:none}
.tri-corner text{font-family:-apple-system,"Segoe UI",Roboto,Arial,sans-serif}
.tri-corner:hover .tri-lab,.tri-corner:focus-visible .tri-lab{text-decoration:underline}
.tri-lab{font-size:18px;font-weight:800}
.tri-sub{font-size:13.5px;font-weight:500;fill:var(--muted)}

/* clean fact list for the driver mechanisms */
.facts{margin:12px 0;padding-left:20px}
.facts li{margin:8px 0;line-height:1.6}
.facts li b{color:var(--ink)}

/* three-column control grid (collapses on tablet/phone) */
.controls.controls3{grid-template-columns:1fr 1fr 1fr;align-items:start}
@media(max-width:760px){.controls.controls3{grid-template-columns:1fr}}

/* rebound slider colours */
.slider-block.base{background:var(--blue-soft)}
.slider-block.ctrl{background:var(--accent-soft)}
.slider-block.loss{background:var(--warm-soft)}
.slider-block.base .val{color:var(--blue)}
.slider-block.ctrl .val{color:var(--accent)}
.slider-block.loss .val{color:#c45a25}
.subslider{margin-top:14px}
.subslider .slider-top .val{font-size:20px}
#trans{background:linear-gradient(90deg,var(--blue) 0%,var(--blue) var(--fill,0%),#c7d6ec var(--fill,0%),#c7d6ec 100%)}
#trans::-webkit-slider-thumb{border:3px solid var(--blue)} #trans::-moz-range-thumb{border:3px solid var(--blue)}
#strength,#duration{background:linear-gradient(90deg,var(--accent) 0%,var(--accent) var(--fill,0%),#c7e0d8 var(--fill,0%),#c7e0d8 100%)}
#strength::-webkit-slider-thumb,#duration::-webkit-slider-thumb{border:3px solid var(--accent)}
#strength::-moz-range-thumb,#duration::-moz-range-thumb{border:3px solid var(--accent)}
#loss{background:linear-gradient(90deg,var(--warm) 0%,var(--warm) var(--fill,0%),#f4cdb6 var(--fill,0%),#f4cdb6 100%)}
#loss::-webkit-slider-thumb{border:3px solid var(--warm)} #loss::-moz-range-thumb{border:3px solid var(--warm)}

/* rebound indicator box */
.rebound-indicator{display:flex;align-items:center;gap:14px;margin:18px 0 4px;
  border:1px solid var(--line);border-radius:14px;padding:16px 20px;background:var(--bg);
  transition:background .15s ease,border-color .15s ease}
@media(max-width:520px){.rebound-indicator{flex-direction:column;align-items:flex-start;gap:8px}}
.rebound-indicator.lvl-none{background:var(--accent-soft);border-color:#bfe0d8}
.rebound-indicator.lvl-mild{background:var(--warm-soft);border-color:#f1c4a8}
.rebound-indicator.lvl-strong{background:var(--danger-soft);border-color:#e9b6bf}
.rebound-indicator .rb-msg{font-size:15px;font-weight:600}
.rebound-indicator.lvl-none .rb-msg{color:var(--accent)}
.rebound-indicator.lvl-mild .rb-msg{color:#c45a25}
.rebound-indicator.lvl-strong .rb-msg{color:var(--danger)}
.rebound-chip{display:inline-block;font-size:14px;font-weight:800;padding:6px 16px;border-radius:999px;white-space:nowrap;flex:none}
.chip-none{background:#fff;color:var(--accent)}
.chip-mild{background:#fff;color:#c45a25}
.chip-strong{background:#fff;color:var(--danger)}

/* chart panel labels */
.chart-label{font-size:13px;font-weight:750;color:var(--ink);margin:20px 0 4px}
.chart-label .muted{font-weight:500}

/* side-by-side chart panels */
.chart-grid{display:grid;grid-template-columns:1fr 1fr;gap:8px 26px;align-items:start;margin-top:6px}
@media(max-width:760px){.chart-grid{grid-template-columns:1fr}}
.chart-grid .chart-label{margin-top:6px}

/* legend swatches */
.rb-legend{display:flex;flex-wrap:wrap;gap:6px 18px;font-size:13px;margin:14px 0 0}
.rb-legend span{display:inline-flex;align-items:center;gap:7px}
.rb-legend i{width:14px;height:14px;border-radius:4px;display:inline-block}

/* ============================================================
   Seasonality lesson (seasonality.html)
   ============================================================ */
/* three control blocks: season (blue), SMC schedule (accent), coverage (warm) */
.slider-block.season{background:var(--blue-soft)}
.slider-block.smc{background:var(--accent-soft)}
.slider-block.cover{background:var(--warm-soft)}
.slider-block.season .val{color:var(--blue)}
.slider-block.smc .val{color:var(--accent)}
.slider-block.cover .val{color:#c45a25}
/* the seasonality value is a word ("highly seasonal"), not a number: keep it on one
   line at a size that sits with the label rather than dwarfing it */
.slider-block.season > .slider-top .val{font-size:16px;white-space:nowrap}
#seasonality,#peakday{background:linear-gradient(90deg,var(--blue) 0%,var(--blue) var(--fill,0%),#c7d6ec var(--fill,0%),#c7d6ec 100%)}
#seasonality::-webkit-slider-thumb,#peakday::-webkit-slider-thumb{border:3px solid var(--blue)}
#seasonality::-moz-range-thumb,#peakday::-moz-range-thumb{border:3px solid var(--blue)}
#nrounds,#spacing,#firstround{background:linear-gradient(90deg,var(--accent) 0%,var(--accent) var(--fill,0%),#c7e0d8 var(--fill,0%),#c7e0d8 100%)}
#nrounds::-webkit-slider-thumb,#spacing::-webkit-slider-thumb,#firstround::-webkit-slider-thumb{border:3px solid var(--accent)}
#nrounds::-moz-range-thumb,#spacing::-moz-range-thumb,#firstround::-moz-range-thumb{border:3px solid var(--accent)}
#coverage{background:linear-gradient(90deg,var(--warm) 0%,var(--warm) var(--fill,0%),#f4cdb6 var(--fill,0%),#f4cdb6 100%)}
#coverage::-webkit-slider-thumb{border:3px solid var(--warm)} #coverage::-moz-range-thumb{border:3px solid var(--warm)}

/* segmented "who is reached" toggle */
/* visually hidden, still announced by screen readers (used for debounced readout updates) */
.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}
.seg-label{font-size:15px;font-weight:700;margin:16px 0 6px;color:var(--ink)}
.seg{display:flex;gap:4px;background:rgba(255,255,255,.7);border:1px solid #f0c9b3;
  border-radius:10px;padding:4px}
.seg-btn{flex:1 1 0;min-width:0;border:none;background:transparent;cursor:pointer;
  font-family:inherit;font-size:12.5px;font-weight:700;color:var(--muted);
  padding:8px 6px;border-radius:7px;line-height:1.2;transition:background .12s ease,color .12s ease}
.seg-btn:hover{background:rgba(255,255,255,.6);color:#c45a25}
.seg-btn.active{background:#fff;color:#c45a25;box-shadow:0 1px 3px rgba(20,30,40,.14)}
.seg-btn:focus-visible{outline:2px solid var(--warm);outline-offset:2px}

/* "optimise timing" button: searches start-day + spacing for maximum cases averted */
.opt-btn{margin-top:14px;width:100%;border:none;cursor:pointer;font-family:inherit;
  font-size:13px;font-weight:700;color:#fff;background:var(--accent);
  padding:10px 12px;border-radius:9px;line-height:1.2;
  transition:filter .12s ease,opacity .12s ease}
.opt-btn:hover{filter:brightness(.93)}
.opt-btn:disabled{opacity:.6;cursor:default}
.opt-btn:focus-visible{outline:2px solid var(--accent);outline-offset:2px}
/* pulse the "cases averted" readout when the search settles */
@keyframes readoutFlash{0%{transform:scale(1)}40%{transform:scale(1.12)}100%{transform:scale(1)}}
.readout.flash{animation:readoutFlash .5s ease}

/* ============================================================
   Age-distribution explainer (age-distribution.html)
   ============================================================ */
/* single transmission-intensity slider (blue). A distinct class from .eir so the word-value
   sizing here does not affect the numeric .eir slider on the nonlinearities page. */
.slider-block.intensity{background:var(--blue-soft)}
.slider-block.intensity .val{color:var(--blue);font-size:16px;white-space:nowrap}
#intensity{background:linear-gradient(90deg,var(--blue) 0%,var(--blue) var(--fill,0%),#c7d6ec var(--fill,0%),#c7d6ec 100%)}
#intensity::-webkit-slider-thumb{border:3px solid var(--blue)} #intensity::-moz-range-thumb{border:3px solid var(--blue)}
/* U5 / 5-15 / 15+ case-share bar (second visualisation) */
.agebar{display:flex;height:46px;border-radius:12px;overflow:hidden;border:1px solid var(--line);margin:6px 0 0}
.agebar .seg{display:flex;align-items:center;justify-content:center;color:#fff;font-weight:800;font-size:14px;
  min-width:0;overflow:hidden;white-space:nowrap;transition:width .18s ease;
  text-shadow:0 1px 2px rgba(0,0,0,.35)}   /* lift the white % labels clear of WCAG AA on the mid-tone bands */
.agebar .seg + .seg{border-left:1px solid #fff}   /* crisp divider between adjacent bands */
.agebar .seg.u5{background:#c45a25}                /* darker warm: clears white-text contrast, matches the U5 readout */
.agebar .seg.mid{background:var(--accent)}
.agebar .seg.ad{background:var(--blue)}