/* HL Physics Notebook — shared styles.
   Look: ruled notebook paper, red-pen headings (Caveat), blue-ink body (Lexend). */
:root{
  --paper:#FBFCFE; --rule:#E3ECF6; --sheet:#FFFFFF; --ink:#1E3A8A; --text:#1E2A44; --muted:#556079;
  --red:#C62828; --green:#2E7D32; --note:#FFF4A8; --note-ink:#3B3000; --line:#D3E2F2; --soft:#EEF3FA;
  --display:"Caveat","Segoe Print",cursive; --hand:"Kalam","Comic Sans MS",cursive; --body:"Lexend",system-ui,-apple-system,"Segoe UI",sans-serif;
}
@media (prefers-color-scheme:dark){:root:not([data-theme="light"]){
  --paper:#12161D; --rule:#1C2330; --sheet:#1A202B; --ink:#A9C6FF; --text:#E3E8F2; --muted:#9AA6BC;
  --red:#FF8A80; --green:#8BD18F; --note:#4A4220; --note-ink:#FFF2B3; --line:#2B3547; --soft:#222A38; color-scheme:dark}}
:root[data-theme="dark"]{
  --paper:#12161D; --rule:#1C2330; --sheet:#1A202B; --ink:#A9C6FF; --text:#E3E8F2; --muted:#9AA6BC;
  --red:#FF8A80; --green:#8BD18F; --note:#4A4220; --note-ink:#FFF2B3; --line:#2B3547; --soft:#222A38; color-scheme:dark}

*{box-sizing:border-box}
[hidden]{display:none!important}
html{scroll-behavior:smooth}
body{margin:0;background:var(--paper);background-image:repeating-linear-gradient(180deg,transparent 0,transparent 31px,var(--rule) 31px,var(--rule) 32px);
  color:var(--text);font-family:var(--body);font-size:17px;line-height:1.65}
a{color:var(--ink)} a:hover{color:var(--red)}
:focus-visible{outline:3px solid var(--red);outline-offset:2px}
img{max-width:100%}
.wrap{max-width:1120px;margin:0 auto;padding-inline:20px}

/* header */
.site-head{background:var(--paper);border-bottom:2px solid var(--red);position:sticky;top:env(safe-area-inset-top,0px);z-index:20}
.site-head .wrap{display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;gap:8px 20px;padding-block:12px}
.brand{text-decoration:none;display:flex;flex-direction:column;line-height:1}
.brand b{font-family:var(--display);font-size:38px;color:var(--red)}
.brand span{font-size:13px;color:var(--muted);margin-top:4px}
.site-nav{display:flex;flex-wrap:wrap;gap:4px}
.site-nav a{padding:10px 14px;border-radius:8px;text-decoration:none;font-size:16px;font-weight:500}
.site-nav a[aria-current="page"]{background:var(--soft);color:var(--red)}

/* type */
h1,h2,h3{text-wrap:balance}
h1{font-family:var(--display);font-size:clamp(46px,7vw,76px);line-height:1;color:var(--ink);margin:0}
h2{font-family:var(--display);font-size:clamp(36px,5vw,50px);line-height:1.1;color:var(--red);margin:0 0 16px}
h3{font-size:20px;color:var(--ink);margin:0 0 6px}
p{margin:0 0 12px;max-width:68ch}
.eyebrow{font-size:14px;font-weight:600;letter-spacing:.08em;text-transform:uppercase;color:var(--red);margin:0 0 10px}
.lead{font-size:19px;max-width:62ch}
.muted{color:var(--muted)}
.small{font-size:14px}
section.block{padding-block:56px 8px}
.crumbs{font-size:15px;color:var(--muted);padding-top:24px;margin:0}

/* buttons */
.btns{display:flex;flex-wrap:wrap;gap:12px;margin-top:24px}
.btn{display:inline-flex;align-items:center;min-height:48px;padding:12px 22px;border-radius:8px;font:600 16px var(--body);text-decoration:none;border:2px solid var(--ink);cursor:pointer}
.btn.primary{background:var(--red);border-color:var(--red);color:var(--paper)}
.btn.primary:hover{color:var(--paper);filter:brightness(1.08)}
.btn.ghost{background:transparent;color:var(--ink)}
.btn.small{min-height:40px;padding:8px 14px;font-size:14px}

/* hero */
.hero{display:flex;flex-wrap:wrap;gap:40px;align-items:center;padding-block:48px 16px}
.hero>div:first-child{flex:999 1 520px;min-width:0}
.sticky-note{flex:1 1 300px;min-width:0;background:var(--note);color:var(--note-ink);padding:22px 26px;border-radius:3px;transform:rotate(1.2deg);box-shadow:0 6px 18px rgba(30,42,68,.12)}
.sticky-note b{font-family:var(--display);font-size:32px;display:block;line-height:1.1}
.sticky-note ul{margin:8px 0 0;padding-left:20px;font-size:16px}
.byline{margin:28px 0 0;font-size:16px;color:var(--muted)} .byline b{color:var(--ink)}

/* stats */
.stats{display:flex;flex-wrap:wrap;gap:12px;margin-top:12px}
.stat{display:flex;flex-direction:column;padding:12px 18px;background:var(--sheet);border:2px solid var(--line);border-radius:10px;min-width:150px}
.stat.good{border-color:var(--green)}
.stat b{font-family:var(--display);font-size:46px;line-height:1;color:var(--green);font-variant-numeric:tabular-nums}
.stat:not(.good) b{color:var(--ink)}
.stat span{font-size:14px;color:var(--muted)}

/* cards & grids */
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:18px}
.card{display:flex;flex-direction:column;gap:8px;padding:22px;background:var(--sheet);border:2px solid var(--line);border-radius:12px;text-decoration:none;color:var(--text)}
a.card:hover{border-color:var(--red);color:var(--text)}
.card.off{opacity:.75}
.badge{width:48px;height:48px;border-radius:50%;color:#fff;display:flex;align-items:center;justify-content:center;font-family:var(--display);font-size:32px;font-weight:700;flex:none}
.card .top{display:flex;align-items:center;gap:12px}
.card .top b{font-size:19px;color:var(--ink)}
.status{font-size:14px;font-weight:600;color:var(--green)}
.status.soon{color:var(--muted);font-weight:500}
.typecard{padding:22px;background:var(--sheet);border-radius:12px;border-top:6px solid var(--red)}
.typecard b{font-family:var(--display);font-size:32px;color:var(--ink);display:block;line-height:1.1}
.typecard p{font-size:15px;color:var(--muted);margin:6px 0 0}

/* topic list */
.topics{display:flex;flex-direction:column;gap:14px}
.topic{display:flex;flex-wrap:wrap;gap:12px 24px;align-items:center;padding:18px 22px;background:var(--sheet);border:2px solid var(--line);border-radius:12px;text-decoration:none;color:var(--text)}
a.topic:hover{border-color:var(--red);color:var(--text)}
.topic .code{font-family:var(--display);font-size:42px;font-weight:700;color:var(--red);min-width:70px;line-height:1}
.topic .mid{flex:999 1 300px;min-width:0}
.topic .mid b{font-size:20px;color:var(--ink)}
.topic .mid span{display:block;font-size:15px;color:var(--muted)}
.topic .mid .pill{display:inline-block;font-size:12.5px;color:var(--ink)}
.pill{display:inline-block;font-size:12.5px;font-weight:600;padding:3px 10px;border-radius:999px;background:var(--soft);color:var(--ink);vertical-align:middle;margin-left:6px}
.chips{display:flex;flex-wrap:wrap;gap:6px;flex:1 1 240px}
.chip{font-size:13.5px;padding:5px 11px;border-radius:999px;border:1.5px dashed var(--muted);color:var(--muted)}
.chip.on{border:1.5px solid var(--ink);background:var(--ink);color:var(--sheet);font-weight:600}

/* panels */
.panel{background:var(--sheet);border:2px solid var(--line);border-radius:12px;padding:22px 24px;margin:16px 0}
.panel.soon{border-style:dashed}
.note{background:var(--note);color:var(--note-ink);padding:14px 18px;border-radius:3px;margin:16px 0;max-width:72ch}
.callout{display:flex;flex-wrap:wrap;gap:20px;align-items:center;justify-content:space-between;padding:26px 30px;background:var(--ink);color:var(--sheet);border-radius:14px}
.callout h2{color:var(--sheet);margin:0}
.callout p{color:var(--sheet);opacity:.9;margin:6px 0 0}
.callout .btn{background:var(--sheet);color:var(--ink);border-color:var(--sheet)}

/* tables */
.tw{overflow-x:auto}
table{border-collapse:collapse;width:100%;font-size:16px;background:var(--sheet);border-radius:10px}
th,td{text-align:left;padding:10px 14px;border-bottom:1px solid var(--line);vertical-align:top}
th{color:var(--ink)} td.num{font-variant-numeric:tabular-nums}

/* forms */
label.check{display:flex;gap:10px;align-items:flex-start;min-height:36px;cursor:pointer;line-height:1.45;padding-block:4px}
label.check input{width:20px;height:20px;margin-top:2px;accent-color:var(--green);flex:none}
.bar{height:10px;border-radius:999px;background:var(--soft);overflow:hidden}
.bar>div{height:100%;width:0;background:var(--green);transition:width .3s}
input.answer{font:500 17px var(--body);padding:10px 12px;border-radius:8px;border:2px solid var(--line);background:var(--sheet);color:var(--text);width:160px}

/* footer */
.site-foot{border-top:1px solid var(--line);background:var(--paper);margin-top:72px}
.site-foot .wrap{padding-block:24px;display:flex;flex-wrap:wrap;gap:8px 24px;justify-content:space-between;font-size:14px;color:var(--muted)}

@media (max-width:640px){.site-nav a{padding:8px 10px;font-size:15px}.brand b{font-size:32px}}
@media (prefers-reduced-motion:reduce){*{transition:none!important;animation:none!important}html{scroll-behavior:auto}}

/* dark / light switch */
.theme-btn{font:600 15px var(--body);min-height:44px;padding:8px 14px;border-radius:8px;border:2px solid var(--line);background:var(--sheet);color:var(--ink);cursor:pointer;margin-left:4px}
.theme-btn:hover{border-color:var(--red)}

/* folded instructions (12 Oct 2026) */
details.howto{border:2px solid var(--line);border-radius:12px;padding:10px 14px;background:var(--sheet);margin:6px 0 4px}
details.howto>summary{cursor:pointer;font-weight:700;color:var(--ink);list-style:revert}
details.howto[open]>summary{margin-bottom:8px}
details.howto p.small{margin:8px 0 0}

/* slim top bar on phones (12 Oct 2026) */
@media (max-width:640px){
  .site-head .wrap{display:block;padding-block:6px 4px}
  .site-head .brand{display:block}
  .site-head .brand b{font-size:20px}
  .site-head .brand span{display:none}
  nav.site-nav{flex-wrap:nowrap;gap:0;justify-content:space-between;margin-top:2px}
  nav.site-nav a{padding:6px 3px;font-size:13px;white-space:nowrap}
  nav.site-nav .lg{display:none}

  nav.site-nav .theme-btn{padding:3px 8px;border-width:1.5px;min-height:0;font-size:14px}
  nav.site-nav .theme-btn .tl{display:none}
}
@media (max-width:340px){nav.site-nav a{padding:6px 2px;font-size:12px}}
/* practice drawings */
.pfig{margin:12px 0 6px}.pfig svg{width:100%;max-width:340px;height:auto;display:block;overflow:visible}
.pfig .k,.pfig .k2{stroke:var(--text);stroke-width:2;fill:none;stroke-linecap:round}.pfig .k2{fill:var(--text)}
.pfig .g{stroke:var(--muted);stroke-width:1.2}.pfig .m{stroke:var(--text);stroke-width:1.4;fill:none}
.pfig .b{fill:var(--soft);stroke:var(--text);stroke-width:2}.pfig .sl{fill:var(--rule);stroke:var(--text);stroke-width:2}
.pfig .p{fill:var(--sheet);stroke:var(--text);stroke-width:2}.pfig .wa{fill:#4F8FD8;fill-opacity:.18;stroke:#4F8FD8;stroke-width:1.5}
.pfig .a{stroke:var(--red);stroke-width:2.6;stroke-linecap:round}.pfig .ah{fill:var(--red)}
.pfig .v{stroke:var(--green);stroke-width:2.6;stroke-linecap:round}.pfig .vh{fill:var(--green)}
.pfig .t{fill:var(--text);font:600 14px var(--body)}.pfig .s{font-size:13px}.pfig .mu{fill:var(--muted);font-weight:500}
.pfig .gl{stroke:var(--ink);stroke-width:2.6;fill:none;stroke-linecap:round}.pfig .k2a{stroke:var(--text);stroke-width:1.6}.pfig .k2ah{fill:var(--text)}.pfig .gr{stroke:var(--line);stroke-width:1}.pfig .tg{stroke:var(--red);stroke-width:1.8;stroke-dasharray:6 4}.pfig .ms{stroke:var(--muted);stroke-width:9;stroke-opacity:.35;fill:none;stroke-linecap:round}.pfig .at{fill:var(--red)}.pfig .vt{fill:var(--green)}
.pfig.opt svg{max-width:150px}.work .pfig svg{max-width:520px}

[id]{scroll-margin-top:100px}

/* formula boxes in concept builders */
.law{border:2.5px solid var(--red);border-radius:14px 6px 16px 8px;padding:6px 16px;color:var(--red);display:inline-block;max-width:100%}
.law b{font-weight:700}
.law .eq{display:inline-block;margin:0 1.1em 0 .3em}