/* waves.jelia.nyc — shared design system.
   Tokens and component styles are lifted from J's original "The 2.4 GHz Band" page
   (2-4-ghz/) so every chapter reads as the same publication. Change a token here,
   not in a chapter. */

:root{
  --bg:#EDF0F3; --panel:#FFFFFF; --ink:#152130; --muted:#586577; --line:#CAD2DB;
  --accent:#D9661F; --wave:#14798A; --warn:#B8323A; --soft:#F5F7F9;
  /* extra series colours for multi-line canvases (E field, B field, third trace) */
  --efield:#D9661F; --bfield:#2F62C4; --third:#7A4FC0;
  --f-display:"Bricolage Grotesque","Segoe UI",system-ui,sans-serif;
  --f-body:"IBM Plex Sans","Segoe UI",system-ui,sans-serif;
  --f-mono:"IBM Plex Mono",ui-monospace,Menlo,Consolas,monospace;
  color-scheme:light;
}
@media (prefers-color-scheme: dark){:root:not([data-theme="light"]){
  --bg:#0F151C; --panel:#16202B; --ink:#E4EAF1; --muted:#97A5B5; --line:#2B3846;
  --accent:#F08A45; --wave:#45B4C6; --warn:#E5626A; --soft:#1B2633;
  --efield:#F08A45; --bfield:#6E9BF0; --third:#B08CF0; color-scheme:dark}}
:root[data-theme="dark"]{
  --bg:#0F151C; --panel:#16202B; --ink:#E4EAF1; --muted:#97A5B5; --line:#2B3846;
  --accent:#F08A45; --wave:#45B4C6; --warn:#E5626A; --soft:#1B2633;
  --efield:#F08A45; --bfield:#6E9BF0; --third:#B08CF0; color-scheme:dark}

*{box-sizing:border-box}
html{scroll-padding-top:72px}
body{margin:0;background:var(--bg);color:var(--ink);font:16px/1.6 var(--f-body);padding:0 16px}
img{max-width:100%}
a{color:var(--wave);text-underline-offset:2px}
[hidden]{display:none!important}

.wrap{max-width:980px;margin:0 auto;padding-block:40px 64px;display:grid;gap:56px}
h1,h2,h3{font-family:var(--f-display);text-wrap:balance;margin:0;line-height:1.1}
h1{font-size:clamp(2.6rem,7vw,4.6rem);font-weight:800;letter-spacing:-.02em}
h1 em,h2 em{font-style:normal;color:var(--accent)}
h2{font-size:clamp(1.5rem,3.4vw,2.1rem);font-weight:700}
h3{font-size:1.2rem;font-weight:700}
p{margin:0;max-width:65ch}
ul,ol{margin:0;padding-left:1.3em;max-width:65ch;display:grid;gap:6px}
.eyebrow{font:500 .75rem/1 var(--f-mono);letter-spacing:.12em;text-transform:uppercase;color:var(--muted)}
.mono{font-family:var(--f-mono)}
section{display:grid;gap:18px}
.prose{display:grid;gap:14px}
.lede{font-size:1.12rem;color:var(--muted)}
.facts{display:grid;grid-template-columns:repeat(auto-fit,minmax(200px,1fr));gap:1px;background:var(--line);border:1px solid var(--line);border-radius:6px;overflow:hidden}
.facts div{background:var(--panel);padding:16px 18px;display:grid;gap:4px}
.facts b{font:600 1.5rem/1.2 var(--f-mono);font-variant-numeric:tabular-nums}
.facts span{color:var(--muted);font-size:.9rem}
.note{border-left:3px solid var(--accent);padding:12px 16px;background:var(--panel);border-radius:0 6px 6px 0;max-width:none}
.note strong{color:var(--accent)}

/* equation block: the one formula a section hangs on, set big, with a plain-English gloss */
.eq{background:var(--panel);border:1px solid var(--line);border-radius:8px;padding:16px 20px;display:grid;gap:6px}
.eq .f{font:600 clamp(1.1rem,3vw,1.5rem)/1.3 var(--f-mono);overflow-wrap:anywhere}
.eq .g{color:var(--muted);font-size:.95rem}

/* "go deeper" — optional maths and detail, collapsed so the main read stays light */
details.deep{background:var(--panel);border:1px solid var(--line);border-radius:8px;padding:0 18px}
details.deep>summary{cursor:pointer;padding:14px 0;font:600 .9rem var(--f-mono);color:var(--wave);list-style:none}
details.deep>summary::before{content:"+ ";}
details.deep[open]>summary::before{content:"− ";}
details.deep>div{padding:0 0 18px;display:grid;gap:12px}

/* player (narrated walkthrough) — same look as the 2.4 GHz original */
.player{background:var(--panel);border:1px solid var(--line);border-radius:8px;padding:14px;display:grid;gap:12px}
.screen{position:relative;aspect-ratio:16/9;max-width:100%;background:var(--soft);border-radius:4px;overflow:hidden}
.screen canvas{position:absolute;inset:0;width:100%;height:100%}
.bigplay{position:absolute;right:16px;bottom:16px;font:600 .95rem var(--f-body);background:var(--accent);color:#fff;border:0;border-radius:999px;padding:10px 18px;cursor:pointer}
/* phones: the play pill would sit on top of the scene's corner labels, so shrink it */
@media (max-width:560px){.bigplay{right:8px;bottom:8px;padding:6px 12px;font-size:.8rem;opacity:.92}}
.caption{min-height:3.4em;font-size:1.05rem;padding:2px 4px}
.controls{display:flex;align-items:center;gap:12px;flex-wrap:wrap}
.btn{font:600 .9rem var(--f-body);background:var(--ink);color:var(--panel);border:0;border-radius:4px;padding:8px 14px;cursor:pointer;min-width:5.5em}
.track{flex:1 1 200px;height:10px;background:var(--soft);border:1px solid var(--line);border-radius:5px;position:relative;cursor:pointer}
.track .fill{position:absolute;inset:0 auto 0 0;background:var(--accent);border-radius:5px}
.track i{position:absolute;top:-3px;bottom:-3px;width:1px;background:var(--muted);opacity:.5}
.time{font:500 .85rem var(--f-mono);color:var(--muted);font-variant-numeric:tabular-nums}
.voice{display:flex;align-items:center;gap:6px;font-size:.9rem;color:var(--muted)}
.chapters{list-style:none;margin:0;padding:0;display:grid;grid-template-columns:repeat(auto-fit,minmax(150px,1fr));gap:6px;max-width:none}
.chapters button{width:100%;text-align:left;font:500 .85rem var(--f-body);color:var(--ink);background:transparent;border:1px solid var(--line);border-radius:4px;padding:8px 10px;cursor:pointer;display:grid;gap:2px}
.chapters button small{font:500 .7rem var(--f-mono);color:var(--muted);letter-spacing:.08em}
.chapters button[aria-current="true"]{border-color:var(--accent);background:var(--soft)}
button:focus-visible,input:focus-visible,select:focus-visible,a:focus-visible{outline:2px solid var(--accent);outline-offset:2px}

/* lab instruments */
.lab{background:var(--panel);border:1px solid var(--line);border-radius:8px;padding:18px;display:grid;gap:16px}
.lab canvas{width:100%;height:260px;display:block;touch-action:none}
.lab canvas.tall{height:360px}
.lab canvas.short{height:190px}
input[type=range]{width:100%;accent-color:var(--accent)}
.ctl{display:grid;gap:4px}
.ctl label{font:500 .78rem var(--f-mono);letter-spacing:.06em;text-transform:uppercase;color:var(--muted);display:flex;justify-content:space-between;gap:8px}
.ctl label b{color:var(--ink);font-weight:600;text-transform:none;letter-spacing:0}
.ctlgrid{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:14px}
.presets{display:flex;flex-wrap:wrap;gap:6px}
.chip{font:500 .8rem var(--f-body);background:var(--soft);color:var(--ink);border:1px solid var(--line);border-radius:999px;padding:5px 12px;cursor:pointer}
.chip[aria-pressed="true"]{border-color:var(--accent);color:var(--accent)}
.readout{display:grid;grid-template-columns:repeat(auto-fit,minmax(170px,1fr));gap:14px}
.readout div{display:grid;gap:2px;min-width:0}
.readout b{font:600 1.15rem/1.3 var(--f-mono);font-variant-numeric:tabular-nums;overflow-wrap:anywhere}
.readout span{font-size:.78rem;color:var(--muted);text-transform:uppercase;letter-spacing:.08em;font-family:var(--f-mono)}
.hint{font-size:.85rem;color:var(--muted)}

/* table + glossary */
.tablewrap{overflow-x:auto;border:1px solid var(--line);border-radius:8px;background:var(--panel)}
table{border-collapse:collapse;width:100%;min-width:620px;font-size:.95rem}
th,td{text-align:left;padding:12px 14px;border-bottom:1px solid var(--line);vertical-align:top}
th{font:600 .75rem var(--f-mono);letter-spacing:.08em;text-transform:uppercase;color:var(--muted)}
tr:last-child td{border-bottom:0}
td:first-child{font:600 1rem var(--f-mono);white-space:nowrap}
tr.hl td:first-child{color:var(--accent)}
dl{display:grid;grid-template-columns:minmax(120px,max-content) 1fr;gap:10px 22px;margin:0}
dt{font:600 .95rem var(--f-mono)}
dd{margin:0;color:var(--muted);max-width:60ch}
@media (max-width:560px){dl{grid-template-columns:1fr;gap:2px}dd{margin-bottom:10px}}
footer{color:var(--muted);font-size:.85rem}

/* site chrome: top bar + prev/next pager, rendered by site.js from one chapter list */
.topbar{position:sticky;top:0;z-index:5;margin:0 -16px;padding:10px 16px;background:color-mix(in srgb,var(--bg) 88%,transparent);backdrop-filter:blur(8px);border-bottom:1px solid var(--line)}
.topbar .in{max-width:980px;margin:0 auto;display:flex;align-items:center;gap:14px;flex-wrap:wrap}
.topbar .brand{font:800 1.05rem var(--f-display);color:var(--ink);text-decoration:none;display:flex;align-items:center;gap:8px}
.topbar .brand svg{color:var(--accent)}
.topbar .where{font:500 .75rem var(--f-mono);letter-spacing:.08em;text-transform:uppercase;color:var(--muted);flex:1;min-width:0;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.topbar select{font:500 .85rem var(--f-body);background:var(--panel);color:var(--ink);border:1px solid var(--line);border-radius:4px;padding:6px 8px;max-width:100%}
.themebtn{font:500 .8rem var(--f-mono);background:transparent;color:var(--muted);border:1px solid var(--line);border-radius:4px;padding:6px 10px;cursor:pointer}
.pager{display:grid;grid-template-columns:1fr 1fr;gap:12px}
.pager a{display:grid;gap:4px;padding:14px 16px;border:1px solid var(--line);border-radius:8px;background:var(--panel);text-decoration:none;color:var(--ink)}
.pager a small{font:500 .7rem var(--f-mono);letter-spacing:.1em;text-transform:uppercase;color:var(--muted)}
.pager a b{font:700 1.05rem var(--f-display)}
.pager a.next{text-align:right;grid-column:2}
@media (max-width:560px){.pager{grid-template-columns:1fr}.pager a.next{grid-column:1}}

/* hub: chapter cards */
.parts{display:grid;gap:36px}
.part{display:grid;gap:14px}
.cards{display:grid;grid-template-columns:repeat(auto-fit,minmax(260px,1fr));gap:12px}
.card{display:grid;gap:8px;align-content:start;padding:18px;border:1px solid var(--line);border-radius:8px;background:var(--panel);text-decoration:none;color:var(--ink);transition:border-color .18s,transform .18s,background-color .18s,box-shadow .18s}
.card:hover,.card:focus-visible{border-color:var(--accent);transform:translateY(-2px);background:color-mix(in srgb,var(--panel) 86%,var(--accent));box-shadow:0 6px 18px color-mix(in srgb,var(--accent) 18%,transparent)}
.card:hover b,.card:focus-visible b{color:var(--accent)}
.card small{font:500 .7rem var(--f-mono);letter-spacing:.1em;text-transform:uppercase;color:var(--muted)}
.card b{font:700 1.25rem/1.15 var(--f-display)}
.card span{color:var(--muted);font-size:.93rem}
.card.star{border-color:var(--accent)}

/* hub flair (J 2026-10-06): tiles take the neon of J's logo, one colour per part, glowing edge + tinted hover */
.part{--pc:var(--accent)}
.part:nth-child(1){--pc:#22D3B4}.part:nth-child(2){--pc:#4F7DFF}.part:nth-child(3){--pc:#A35CFF}
.part:nth-child(4){--pc:#FF8A3D}.part:nth-child(5){--pc:#E0E44A}
.part>.eyebrow{color:var(--pc)}
.part .card{position:relative;overflow:hidden;border-color:color-mix(in srgb,var(--pc) 35%,var(--line))}
.part .card::before{content:"";position:absolute;inset:0 0 auto 0;height:3px;background:var(--pc);box-shadow:0 0 12px var(--pc)}
.part:nth-child(4) .card::before,.part:nth-child(5) .card::before{background:linear-gradient(90deg,#FF3B5C,#FF9F1C,#F5E642,#3DDC84,#2EC5FF,#8E5CFF,#E05CFF)}
.part .card:hover,.part .card:focus-visible{border-color:var(--pc);background:color-mix(in srgb,var(--panel) 86%,var(--pc));
  box-shadow:0 6px 20px color-mix(in srgb,var(--pc) 28%,transparent)}
.part .card:hover b,.part .card:focus-visible b{color:var(--pc)}
.part .card small{color:color-mix(in srgb,var(--pc) 70%,var(--muted))}
/* the contents heading gets the logo's run as a neon underline */
.neon-rule{height:3px;border-radius:3px;max-width:420px;background:linear-gradient(90deg,#22D3B4,#4F7DFF,#A35CFF,#FF3B5C,#FF9F1C,#F5E642,#3DDC84);box-shadow:0 0 12px rgba(120,120,255,.45)}
@media (prefers-color-scheme:light){:root:not([data-theme="dark"]) .part:nth-child(5){--pc:#9A8F00}}
:root[data-theme="light"] .part:nth-child(5){--pc:#9A8F00}