:root{--bg:#07090d;--panel:#11161d;--panel2:#161d26;--text:#eef3f7;--muted:#aeb9c4;--line:#2c3744;--gold:#d7b46a;--blue:#a8c4df;--max:1200px}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--bg);color:var(--text);font:16px/1.65 system-ui,-apple-system,"Segoe UI",sans-serif}a{color:#d9ebfb;text-decoration:none}a:hover{text-decoration:underline}.wrap{width:min(var(--max),calc(100% - 32px));margin:auto}
.whd-site-header{position:sticky;top:0;z-index:40;background:#090d12;border-bottom:1px solid var(--line)}.whd-brand-row{min-height:58px;display:flex;align-items:center;justify-content:space-between;gap:18px}.brand{display:inline-flex;align-items:center;gap:10px;text-decoration:none!important}.brand-mark{display:grid;place-items:center;width:34px;height:34px;border:1px solid var(--line);border-radius:10px;background:#111823}.brand-copy{display:grid;line-height:1.08}.brand-copy strong{color:#fff;font-size:.96rem}.brand-copy small{margin-top:3px;color:var(--muted);font-size:.66rem;letter-spacing:.11em;text-transform:uppercase}.whd-visitor{margin-left:auto;white-space:nowrap;text-align:right;color:var(--muted);font-size:.78rem;font-weight:750}.whd-subnav{border-top:1px solid rgba(255,255,255,.055);background:#070b10}.nav{padding:7px 0;display:flex;gap:8px;flex-wrap:wrap}.nav a{padding:5px 8px;border-radius:7px;color:#bdcbd8;font-size:.78rem}.nav a:hover{background:#141b24;color:#fff;text-decoration:none}
.crumb{padding:18px 0 4px;color:var(--muted);font-size:.9rem}.crumb b{color:#fff}.crumb span{padding:0 7px;color:#647384}
.hero{padding:28px 0 24px}.hero-grid{display:grid;grid-template-columns:minmax(0,1.25fr) minmax(330px,.75fr);gap:22px;align-items:start}.kicker{color:var(--gold);font-size:.78rem;font-weight:800;letter-spacing:.16em;text-transform:uppercase}h1{font-size:clamp(2.6rem,5vw,5rem);line-height:1;letter-spacing:-.045em;margin:.2em 0 .2em}.lede,.lead{color:#c7d1db;font-size:1.08rem;max-width:70ch}.hero figure{margin:0}.hero figure img,.page-photo img{display:block;width:100%;height:310px;object-fit:cover;object-position:center 25%;border:1px solid var(--line);border-radius:16px;background:#111}.hero figcaption,.page-photo figcaption{font-size:.78rem;color:var(--muted);margin-top:7px}.stats{display:grid;grid-template-columns:repeat(4,1fr);gap:11px;margin-top:25px}.stat{background:var(--panel);border:1px solid var(--line);border-radius:12px;padding:16px}.stat strong{font-size:1.55rem;display:block}.stat small{color:var(--muted)}
.section{border-top:1px solid var(--line);padding:44px 0}.head{display:flex;justify-content:space-between;align-items:end;gap:24px;margin-bottom:22px}h2{font-size:clamp(1.8rem,3.4vw,2.8rem);letter-spacing:-.03em;margin:0}.intro{max-width:75ch;color:var(--muted)}
.searchbox{background:var(--panel);border:1px solid var(--line);border-radius:16px;padding:22px}.filters{display:grid;grid-template-columns:2fr repeat(5,1fr);gap:11px}label{display:block;font-size:.76rem;letter-spacing:.07em;text-transform:uppercase;font-weight:800;color:#cbd5df;margin-bottom:6px}input,select,button{width:100%;background:#0a0f15;border:1px solid #364453;color:var(--text);border-radius:9px;padding:11px 12px;font:inherit}button{cursor:pointer;font-weight:800}button.primary{background:var(--gold);border-color:var(--gold);color:#111}.actions{display:flex;gap:10px;margin-top:14px;flex-wrap:wrap}.actions button{width:auto}.summary{color:var(--muted);margin:16px 0 9px}.results,.records{display:grid;gap:10px}.result,.record{background:#0c1117;border:1px solid var(--line);border-radius:12px;padding:16px}.result h3,.record h2,.record h3{margin:0 0 5px;font-size:1.03rem}.meta{color:var(--blue);font-size:.82rem}.result p,.record p{margin:5px 0 0;color:#cbd4dc}
.browse-hubs{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:16px}.browse-hub{display:flex;flex-direction:column;align-items:flex-start;min-height:184px;padding:20px;border:1px solid var(--line);border-radius:14px;background:linear-gradient(155deg,#151d27,#0d131a);text-decoration:none!important}.browse-hub:hover{border-color:#55708a;background:#172331}.browse-hub .hub-label{display:block;width:100%;margin:0 0 10px;color:var(--gold);font-size:.76rem;font-weight:850;letter-spacing:.08em;text-transform:uppercase}.browse-hub strong{display:block;width:100%;margin:0 0 11px;color:#fff;font-size:1.24rem;line-height:1.22}.browse-hub>span:last-child{color:var(--muted);font-size:.92rem;line-height:1.55}
.grid4{display:grid;grid-template-columns:repeat(4,1fr);gap:12px}.grid3{display:grid;grid-template-columns:repeat(3,1fr);gap:12px}.card{background:var(--panel);border:1px solid var(--line);border-radius:14px;padding:18px}.card h3{margin:4px 0 8px}.card p{color:#c4ced8;margin:0}.card em{font-style:normal;color:var(--gold);font-size:.78rem;font-weight:800}
.timeline{list-style:none;padding:0 0 0 24px;margin:0;border-left:2px solid #354251}.timeline li{position:relative;padding:0 0 25px 18px}.timeline li:before{content:"";position:absolute;left:-31px;top:7px;width:12px;height:12px;background:var(--gold);border-radius:50%}.timeline time{display:block;color:var(--gold);font-size:.8rem;font-weight:800}.timeline strong{display:block}.timeline p{margin:3px 0;color:var(--muted)}
.collapsible{border:1px solid var(--line);border-radius:14px;background:rgba(14,19,25,.58);overflow:hidden}.collapsible>summary{list-style:none;cursor:pointer;padding:18px 20px;display:flex;align-items:center;justify-content:space-between;gap:18px;background:#0d1218}.collapsible>summary::-webkit-details-marker{display:none}.collapsible>summary>span:first-child{display:grid;gap:3px}.collapsible>summary strong{font-size:clamp(1.25rem,2.7vw,1.9rem);line-height:1.15;color:#fff}.collapsible>summary:after{content:'＋';font-size:1.45rem;color:var(--gold);font-weight:800}.collapsible[open]>summary:after{content:'−'}.collapsible-body{padding:20px}.collapse-label{color:var(--gold);font-size:.73rem;font-weight:850;letter-spacing:.12em;text-transform:uppercase}.collapse-sub{color:var(--muted);font-size:.88rem}
.sources{display:grid;gap:9px}.sources a{background:var(--panel);border:1px solid var(--line);border-radius:10px;padding:12px 14px}.note,.source-note{border-left:3px solid var(--gold);background:#10171f;padding:12px 14px;color:#c7d2dc;margin-top:18px}.crawl-record{border-bottom:1px solid #1c2631;padding:13px 0}.crawl-record h3{font-size:1rem;margin:0}.crawl-record p{margin:3px 0;color:var(--muted)}
.az{display:flex;flex-wrap:wrap;gap:7px;margin:20px 0}.az a{display:inline-grid;place-items:center;min-width:34px;height:34px;border:1px solid var(--line);border-radius:8px;background:var(--panel);font-weight:800}.linkgrid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:9px}.linkgrid a{border:1px solid var(--line);background:var(--panel);border-radius:9px;padding:10px 12px}.group{margin:0 0 32px}.group h2{color:var(--gold);font-size:1.5rem}.pager{display:flex;gap:10px;flex-wrap:wrap;margin:20px 0}.pill{border:1px solid var(--line);border-radius:999px;padding:6px 10px;background:var(--panel)}
.page-photo{margin:4px 0 30px;border:1px solid var(--line);border-radius:14px;overflow:hidden;background:#0c1117}.page-photo img{border:0;border-radius:0;height:min(360px,38vw);min-height:220px}.page-photo figcaption{padding:8px 12px;margin:0}.seo-related{margin:22px 0;padding:16px 18px;border:1px solid var(--line);border-radius:12px;background:#0e141c}.seo-related h2{font-size:1.15rem;margin:0 0 8px}.seo-related p{margin:0 0 8px;color:var(--muted)}.seo-related-links{display:flex;gap:8px;flex-wrap:wrap}.seo-related-links a{display:inline-block;border:1px solid var(--line);border-radius:999px;background:var(--panel);padding:6px 10px;font-weight:750}
footer{border-top:1px solid var(--line);padding:28px 0;color:var(--muted)}.foot{display:flex;justify-content:space-between;gap:20px;flex-wrap:wrap}
@media(max-width:1050px){.filters{grid-template-columns:1fr 1fr 1fr}.hero-grid{grid-template-columns:1fr}.hero figure img{height:auto;aspect-ratio:16/9}.browse-hubs{grid-template-columns:1fr 1fr}.grid4{grid-template-columns:1fr 1fr}.grid3{grid-template-columns:1fr 1fr}}
@media(max-width:680px){.filters,.browse-hubs,.grid4,.grid3,.stats,.linkgrid{grid-template-columns:1fr}.nav{display:flex;overflow-x:auto;flex-wrap:nowrap}.nav a{white-space:nowrap}.whd-visitor{font-size:.67rem}h1{font-size:2.7rem}.page-photo img{height:auto;min-height:0;aspect-ratio:16/9}}


/* Einstein concepts + grouped search controls */
select optgroup{color:var(--gold);background:#091019;font-weight:800}select optgroup option{color:var(--text);background:#0a0f15;font-weight:500;padding-left:10px}
.theory-grid{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:12px}.theory-card{display:flex;min-height:210px;flex-direction:column;padding:18px;border:1px solid var(--line);border-radius:14px;background:linear-gradient(155deg,#151d27,#0d131a);text-decoration:none!important}.theory-card:hover{border-color:#59738d;background:#182432}.theory-card .theory-year{color:var(--gold);font-size:.75rem;font-weight:850;letter-spacing:.08em;text-transform:uppercase}.theory-card strong{margin:10px 0 8px;color:#fff;font-size:1.18rem;line-height:1.2}.theory-card>span:nth-of-type(2){color:var(--muted);font-size:.9rem;line-height:1.55}.theory-card em{margin-top:auto;padding-top:14px;color:var(--blue);font-style:normal;font-size:.82rem;font-weight:850}
.concept-hero{display:grid;grid-template-columns:minmax(0,1.3fr) minmax(260px,.7fr);gap:24px;align-items:center}.concept-equation{display:inline-block;margin-top:20px;padding:12px 16px;border:1px solid #52667c;border-radius:12px;background:#0c131b;color:#fff;font:800 clamp(1.05rem,2.1vw,1.45rem)/1.25 ui-monospace,SFMono-Regular,Menlo,monospace}.concept-diagram{display:grid;place-items:center;min-height:220px;border:1px solid var(--line);border-radius:18px;background:radial-gradient(circle at 50% 40%,rgba(168,196,223,.2),transparent 48%),linear-gradient(145deg,#151d27,#0b1118);overflow:hidden}.concept-diagram span{max-width:90%;color:var(--gold);font:900 clamp(1.4rem,4vw,3rem)/1.1 ui-monospace,SFMono-Regular,Menlo,monospace;text-align:center;letter-spacing:.05em;text-shadow:0 0 22px rgba(215,180,106,.22)}
.concept-layout{display:grid;grid-template-columns:minmax(0,1.55fr) minmax(280px,.45fr);gap:18px;padding:20px 0 45px}.concept-main{display:grid;gap:14px}.concept-section{padding:22px;border:1px solid var(--line);border-radius:14px;background:var(--panel)}.concept-section h2{font-size:1.55rem;margin:0 0 10px}.concept-section p{margin:0 0 12px;color:#c8d2dc}.concept-section p:last-child{margin-bottom:0}.concept-side{display:grid;align-content:start;gap:14px}.concept-side .card{padding:18px}.concept-side .sources a{display:block}
.explainer-link{border-color:rgba(215,180,106,.55)!important;color:#ffe2a3!important;background:rgba(215,180,106,.09)!important}
@media(max-width:1050px){.theory-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.concept-hero,.concept-layout{grid-template-columns:1fr}}
@media(max-width:680px){.theory-grid{grid-template-columns:1fr}.concept-diagram{min-height:160px}}


/* 2026-10-03 SEO/usability refinement */
.hero-photo img,.page-photo img{aspect-ratio:16/9}.editorial-box{padding:22px;border:1px solid var(--line);border-radius:14px;background:linear-gradient(155deg,#121a23,#0b1118)}.editorial-box h2{margin:.15em 0 .55em}.editorial-box p{max-width:85ch;color:#c6d0da}.editorial-box a,.foot-links a,.article-byline a{color:var(--blue)}.foot{flex-wrap:wrap}.foot-links{flex:1 1 100%;padding-top:9px;border-top:1px solid var(--line);color:var(--muted)}.article-byline{margin:-10px 0 22px;padding:9px 12px;border-left:3px solid var(--gold);color:var(--muted);font-size:.82rem;background:rgba(215,180,106,.045)}.record-nav{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:10px;margin:0 0 20px}.record-nav a{padding:10px 12px;border:1px solid var(--line);border-radius:10px;background:var(--panel);text-decoration:none;font-size:.82rem;font-weight:750}.record-nav a[rel="next"]{text-align:right}.record-nav a:hover{border-color:#59738d;background:#15202b}@media(max-width:680px){.record-nav{grid-template-columns:1fr}.record-nav a[rel="next"]{text-align:left}}