/* How a Web Page Loads (computer-science/page-load.php). The page chrome is the one-screen layout in
   /css/resource.css and the drawings' line style is net-draw.css. Here: the stage (the URL bar, the picture and
   the waterfall), the narration and the HTML file beside it, and the controls under them. On a laptop or
   desktop it fits one window, the side panels scrolling inside themselves if they must; on a phone it
   stacks. Theme tokens only: each kind of message has its own name below, pointing at a --viz colour. */
:root{--pl-dns:var(--viz-6);--pl-tcp:var(--viz-7);--pl-tls:var(--viz-4);--pl-http:var(--viz-1);--pl-data:var(--viz-3);--pl-dns-t:var(--viz-6-tint);--pl-tcp-t:var(--viz-7-tint);--pl-tls-t:var(--viz-4-tint);--pl-http-t:var(--viz-1-tint);--pl-data-t:var(--viz-3-tint)}

.rp-main{gap:10px}
.pl-grid{flex:1;min-height:0;display:grid;grid-template-columns:minmax(0,1fr) clamp(260px,30vw,370px);grid-template-rows:auto minmax(0,1.3fr) minmax(0,1fr);grid-template-areas:"stage controls" "stage narr" "stage file";gap:10px}
.pl-stage{grid-area:stage;display:flex;flex-direction:column;min-height:0;min-width:0;overflow:hidden}
.pl-controls{grid-area:controls}.pl-narr{grid-area:narr}.pl-file{grid-area:file}

/* ---------- the URL bar ---------- */
.pl-urlbar{position:relative;flex:none;display:flex;align-items:center;gap:10px;padding:7px 12px;border-bottom:1px solid var(--line);background:var(--panel-2);font:13.5px/1.3 var(--font-mono);border-radius:6px 6px 0 0}
.pl-lock{flex:none;font:600 11px/1 var(--font-mono);padding:3px 7px;border-radius:999px;border:1px solid var(--line-strong);color:var(--muted);min-width:26px;text-align:center}
.pl-lock[data-state="shut"]{color:var(--ok);border-color:var(--ok);background:var(--ok-tint)}
.pl-lock[data-state="open"]{color:var(--bad);border-color:var(--bad);background:var(--bad-tint)}
.pl-url{flex:1;min-width:0;overflow-wrap:anywhere;color:var(--ink)}
.pl-url span{transition:color .2s}
.pl-url .u-proto{color:var(--pl-tls)}
.pl-url .u-path{color:var(--pl-data)}
.pl-url.is-split .u-sub{color:var(--accent-b)}
.pl-url.is-split .u-reg{color:var(--ink);font-weight:700}
.pl-url.is-split .u-sld{color:var(--pl-tcp)}
.pl-url.is-split .u-tld{color:var(--pl-dns)}
.pl-url.is-split .u-domain{text-decoration:underline;text-decoration-color:var(--line-strong);text-underline-offset:4px}
.pl-url .u-key{position:absolute;left:8px;right:8px;top:calc(100% + 4px);z-index:2;display:flex;flex-wrap:wrap;gap:4px 10px;padding:5px 8px;background:var(--panel);border:1px solid var(--line);border-radius:5px;box-shadow:var(--shadow);font:600 11px/1.3 var(--font-mono)}
.pl-url .u-key i{font-style:normal}
.pl-url .u-key i::before{content:"";display:inline-block;width:9px;height:9px;border-radius:2px;margin-right:4px;background:currentColor;vertical-align:-1px}
.pl-url .u-key .u-sub{color:var(--accent-b)}.pl-url .u-key .u-reg{color:var(--ink)}.pl-url .u-key .u-sld{color:var(--pl-tcp)}.pl-url .u-key .u-tld{color:var(--pl-dns)}
.pl-clock{flex:none;font-size:12px;color:var(--muted)}

/* ---------- the picture ---------- */
.pl-scene{position:relative;flex:1;min-height:200px;background:var(--panel)}
.pl-scene svg{position:absolute;inset:0;width:100%;height:100%;display:block}
#msgSvg{pointer-events:none}
.pl-wire path{fill:none;stroke:var(--ink-soft);stroke-width:2.2;stroke-linecap:round}
.pl-tree path{fill:none;stroke:var(--line-strong);stroke-width:1.5;stroke-dasharray:4 4}
.pl-entry{fill:var(--ink-soft)}
.pl-cache-box{fill:var(--panel-2);stroke:var(--line);stroke-width:1}
.pl-cache-head{font:600 9.5px var(--font-mono);letter-spacing:.06em;text-transform:uppercase;fill:var(--muted)}
.pl-cache-row{font:10px var(--font-mono);fill:var(--ink)}
.pl-cache-ip{fill:var(--pl-dns)}
.pl-cache-none{fill:var(--muted);font-style:italic}
.pl-ring{fill:none;stroke:var(--accent);stroke-width:2.5;stroke-dasharray:5 4;opacity:.9;animation:pl-spin 6s linear infinite;transform-box:fill-box;transform-origin:center}
@keyframes pl-spin{to{transform:rotate(360deg)}}

/* the messages: a pill for each, coloured by protocol */
.nd-pill.k-dns rect,.nd-pill.k-dns-answer rect{stroke:var(--pl-dns);fill:var(--panel)}
.nd-pill.k-dns text,.nd-pill.k-dns-answer text{fill:var(--pl-dns)}
.nd-pill.k-dns-answer rect{fill:var(--pl-dns-t)}
.nd-pill.k-tcp rect{stroke:var(--pl-tcp);fill:var(--panel)}
.nd-pill.k-tcp text{fill:var(--pl-tcp)}
.nd-pill.k-tls rect{stroke:var(--pl-tls);fill:var(--panel)}
.nd-pill.k-tls text{fill:var(--pl-tls)}
.nd-pill.k-http rect{stroke:var(--pl-http);fill:var(--panel)}
.nd-pill.k-http text{fill:var(--pl-http)}
.nd-pill.k-data rect{stroke:var(--pl-data);fill:var(--pl-data-t);stroke-width:2}
.nd-pill.k-data text{fill:var(--pl-data)}
.nd-pill.is-now rect{stroke-width:2.6}

/* the browser's page, inside the computer's screen */
.pl-scr-bar{fill:var(--panel);opacity:.85}
.pl-scr-spin{fill:none;stroke:var(--accent);stroke-width:1.6;stroke-dasharray:3 3}
.pl-scr-h1{fill:var(--accent)}
.pl-scr-hole{fill:none;stroke:var(--accent);stroke-width:1;stroke-dasharray:2 2;opacity:.7}
.pl-scr-photo{fill:var(--accent-b)}
.pl-scr-map{fill:var(--pl-data)}
.pl-scr-text{stroke:var(--ink-soft);stroke-width:1.6;stroke-linecap:round}
.pl-scr-btn{fill:var(--pl-tcp)}

/* ---------- the waterfall ---------- */
.pl-water{flex:none;border-top:1px solid var(--line);padding:6px 12px 6px;background:var(--panel)}
.pl-water-head{display:flex;align-items:center;justify-content:space-between;gap:4px 12px;flex-wrap:wrap;margin-bottom:3px}
.pl-legend{display:flex;flex-wrap:wrap;gap:2px 10px;margin:0;padding:0;list-style:none;font:10.5px var(--font-mono);color:var(--ink-soft)}
.pl-legend li{display:flex;align-items:center;gap:4px}
.pl-legend i{width:12px;height:8px;border-radius:2px;display:inline-block}
.pl-rows{position:relative}
.pl-row{display:grid;grid-template-columns:150px minmax(0,1fr);align-items:center;height:16px;gap:8px}
.pl-rlab{display:flex;align-items:baseline;gap:6px;min-width:0;font:11px/1 var(--font-mono);white-space:nowrap;overflow:hidden}
.pl-rlab b{color:var(--ink);font-weight:600}
.pl-rlab i{font-style:normal;font-size:9.5px;overflow:hidden;text-overflow:ellipsis}
.h-www{color:var(--accent)}.h-cdn{color:var(--accent-b)}.h-maps{color:var(--pl-tls)}
.pl-track{position:relative;height:10px;border-bottom:1px dotted var(--line)}
.pl-bar{position:absolute;top:0;height:10px;border-radius:2px}
.ph-dns{background:var(--pl-dns)}
.ph-connect{background:var(--pl-tcp)}
.ph-tls{background:var(--pl-tls)}
.ph-wait{background:var(--pl-http-t);box-shadow:inset 0 0 0 1px var(--pl-http)}
.ph-download{background:var(--pl-data)}
.ph-queued{background:repeating-linear-gradient(135deg,var(--line-strong) 0 2px,transparent 2px 5px)}
.pl-axis{height:14px}
.pl-axis .pl-track{border:0;height:14px}
.pl-axis .pl-track span{position:absolute;top:1px;font:9.5px var(--font-mono);color:var(--muted);transform:translateX(-1px);white-space:nowrap}
.pl-cursor{position:absolute;top:0;bottom:14px;width:0;border-left:1.5px solid var(--accent);pointer-events:none}

/* ---------- the narration and the HTML ---------- */
.pl-narr{min-height:0;display:flex;flex-direction:column;overflow:hidden}
.pl-narr-head{flex:none;display:flex;align-items:baseline;gap:10px;padding:10px 14px 6px;border-bottom:1px solid var(--line)}
.pl-narr-head h2{font:700 15px/1.25 var(--font-display);letter-spacing:0;text-transform:none;color:var(--ink)}
.pl-stepno{flex:none;font-size:11px;color:var(--accent);border:1px solid var(--accent);border-radius:999px;padding:1px 7px}
.pl-narr-body{flex:1;min-height:0;overflow:auto;padding:8px 14px 10px;font-size:14px;line-height:1.5;color:var(--ink-soft)}
.pl-narr-body p{margin:0 0 7px}
.pl-narr-body ul{margin:0 0 7px;padding-left:18px}
.pl-narr-body li{margin-bottom:3px}
.pl-narr-body b{color:var(--ink)}
.pl-narr-body pre{margin:4px 0 8px;padding:6px 9px;background:var(--panel-2);border:1px solid var(--line);border-radius:4px;font:12.5px/1.45 var(--font-mono);color:var(--pl-http);white-space:pre-wrap}
.pl-narr-body .nar-note{font-size:12.5px;color:var(--muted)}
.pl-narr-body .u-proto{color:var(--pl-tls)}.pl-narr-body .u-domain{color:var(--accent-b)}.pl-narr-body .u-path{color:var(--pl-data)}
.pl-file{min-height:0;display:flex;flex-direction:column;padding:9px 0 0;overflow:hidden}
.pl-file h2{padding:0 14px 6px;font-family:var(--font-mono);text-transform:none;letter-spacing:.02em}
.pl-code{flex:1;min-height:0;overflow:auto;margin:0;padding:6px 14px 10px;font:11.5px/1.5 var(--font-mono);color:var(--ink-soft);border-top:1px solid var(--line);background:var(--panel-2);white-space:pre}
.pl-code .ln{display:block;min-height:1.5em}
.pl-code .ln.is-hidden{display:none}
.pl-code-wait{color:var(--muted);font-style:italic}
.pl-code .ref{border-radius:3px;padding:0 2px;color:var(--ink);transition:background .2s,box-shadow .2s}
.pl-code .ref.rel{box-shadow:inset 0 -2px 0 var(--accent)}
.pl-code .ref.abs{box-shadow:inset 0 -2px 0 var(--accent-b)}
.pl-code .ref[data-state="found"]{background:var(--warn-tint)}
.pl-code .ref[data-state="loading"]{background:var(--pl-http-t)}
.pl-code .ref[data-state="done"]{background:var(--ok-tint)}
.pl-code .ref[data-state="done"]::after{content:" \2713";color:var(--ok);font-weight:700}
.pl-code .ref.is-now{outline:2px solid var(--focus);outline-offset:1px}

/* ---------- the controls ---------- */
.pl-controls{display:flex;flex-wrap:wrap;align-items:center;gap:8px;padding:8px 10px}
.pl-controls .btn{flex:1 1 0;min-width:0;padding-left:8px;padding-right:8px}
.pl-slider{flex:1 1 100%;display:flex;align-items:center;gap:7px;font:11px var(--font-mono);letter-spacing:.06em;text-transform:uppercase;color:var(--muted)}
.pl-slider input[type=range]{flex:1;min-width:0;accent-color:var(--accent)}
.pl-slider output{color:var(--ink);min-width:36px;font-variant-numeric:tabular-nums}

/* the Explanation */
.objective h4{margin:18px 0 8px;font:700 15px/1.2 var(--font-display);color:var(--accent-deep)}
.mis div{border-left:3px solid var(--bad);padding:2px 0 2px 11px;margin-bottom:8px}
.mis b{display:block;color:var(--ink)}
details.qa{border-top:1px dashed var(--line);padding:6px 0}
details.qa summary{cursor:pointer;color:var(--ink);font-weight:600}
details.qa p{margin:6px 0 0}

/* short laptop screens: a slimmer waterfall */
@media (min-width:901px) and (max-height:700px){
  .pl-row{height:13px}
  .pl-water{padding-top:4px;padding-bottom:4px}
  .pl-controls{padding:6px 10px;gap:6px}
  .pl-controls .btn{padding-top:6px;padding-bottom:6px}
  .pl-water-head{margin-bottom:1px}
  .pl-narr-body{font-size:13.5px}
}
/* ---------- smaller screens: everything stacks, and the page scrolls ---------- */
@media (max-width:900px){
  .pl-grid{grid-template-columns:1fr;grid-template-rows:none;grid-template-areas:"stage" "controls" "narr" "file"}
  .pl-scene{flex:none;height:440px}
  .pl-code{max-height:300px}
}
@media (max-width:640px){
  .pl-scene{height:540px}
  .pl-row{grid-template-columns:96px minmax(0,1fr);height:18px}
  .pl-rlab i{display:none}
  .pl-urlbar{font-size:12px;padding:7px 10px}
  .pl-controls .btn{min-height:42px}
  .pl-slider input[type=range]{height:32px}
}
@media (prefers-reduced-motion:reduce){.pl-ring{animation:none}}