/* Build Theory Magazine reader (magazine.html, js: bt-magazine.js).
   Built on the Cohort 02 design system: paper / ink / graphite, the sun
   gradient, Sora headings, mono labels. Only the reading stage goes dark:
   a desk under a warm lamp, so the pages are the brightest thing on screen. */

:root{--mg-desk:#121214;--mg-desk-2:#1B1B1F;--mg-ratio:1.4145}
html{scroll-behavior:smooth}
@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}}
body{background:var(--bt-paper)}
.mg-k{display:inline-grid;place-items:center;min-width:22px;height:22px;padding:0 5px;margin-right:4px;border-radius:6px;border:1px solid rgba(244,242,236,.22);font:500 11px/1 var(--font-mono);color:var(--fg-on-dark)}

/* ------------------------------------------------------------------ hero */
.mg-hero{position:relative;overflow:hidden;background:var(--bt-paper);padding:0}
.mg-hero::before{content:"";position:absolute;right:-12%;top:-30%;width:70%;aspect-ratio:1;border-radius:50%;background:var(--c02-sun-r);opacity:.5;filter:blur(40px);pointer-events:none}
.mg-hero-in{position:relative;display:grid;grid-template-columns:minmax(0,7fr) minmax(0,5fr);gap:64px;align-items:center;padding-top:88px;padding-bottom:104px}
.mg-hero h1{margin:22px 0 28px}
.mg-hero h1 .u{display:block;color:var(--bt-concrete-700);font-weight:200;margin-top:10px}
.mg-hero h1 .u em{font-style:normal;color:var(--bt-ink);background:linear-gradient(var(--acc),var(--acc)) 0 94%/100% 3px no-repeat;padding-bottom:4px}
.mg-lead{font-size:clamp(17px,calc(16.2px + .22vw),20px);line-height:1.55;color:var(--bt-concrete-700);max-width:46ch;margin:0}
.mg-facts{list-style:none;display:flex;gap:40px;margin:36px 0 0;padding:24px 0 0;border-top:var(--hair)}
.mg-facts li{display:flex;flex-direction:column;gap:6px}
.mg-facts b{font:300 44px/1 var(--font-head);letter-spacing:-.04em;color:var(--bt-ink)}
.mg-facts span{font:500 12px/1.3 var(--font-mono);letter-spacing:.08em;text-transform:uppercase;color:var(--bt-concrete-500)}
.mg-ctas{display:flex;flex-wrap:wrap;gap:12px;margin-top:40px}
.mg-size{font:500 11px/1 var(--font-mono);letter-spacing:.06em;opacity:.6;margin-left:2px}
.mg-meta{margin:18px 0 0;font:500 12px/1 var(--font-mono);letter-spacing:.1em;text-transform:uppercase;color:var(--bt-concrete-500)}

/* The cover, standing on the desk, turned a little towards the reader. */
.mg-cover3d{position:relative;display:block;justify-self:center;width:min(100%,420px);perspective:1600px;text-decoration:none}
.mg-c3-book{position:relative;display:block;transform:rotateY(-16deg) rotateX(4deg) rotateZ(.6deg);transform-origin:40% 50%;transform-style:preserve-3d;transition:transform .9s var(--ez);border-radius:2px 6px 6px 2px;box-shadow:1px 1px 0 #d9d5cb,2px 2px 0 #cfcac0,3px 3px 0 #c6c1b6,4px 4px 0 #bdb8ad,30px 40px 60px -18px rgba(11,11,12,.45),60px 70px 100px -40px rgba(196,72,40,.35)}
.mg-c3-book img{display:block;width:100%;height:auto;border-radius:2px 6px 6px 2px}
.mg-c3-book::before{content:"";position:absolute;inset:0 auto 0 0;width:7%;border-radius:2px 0 0 2px;background:linear-gradient(90deg,rgba(0,0,0,.35),rgba(255,255,255,.12) 40%,rgba(0,0,0,.08) 70%,transparent);pointer-events:none;z-index:1}
.mg-c3-sheen{position:absolute;inset:0;border-radius:inherit;background:linear-gradient(115deg,rgba(255,255,255,0) 30%,rgba(255,255,255,.16) 46%,rgba(255,255,255,0) 60%);background-size:250% 100%;background-position:100% 0;transition:background-position 1.1s var(--ez);pointer-events:none}
.mg-c3-shadow{position:absolute;left:8%;right:-4%;bottom:-34px;height:40px;border-radius:50%;background:radial-gradient(closest-side,rgba(11,11,12,.32),transparent);filter:blur(6px);z-index:-1}
.mg-cover3d:hover .mg-c3-book,.mg-cover3d:focus-visible .mg-c3-book{transform:rotateY(-6deg) rotateX(2deg) translateY(-6px)}
.mg-cover3d:hover .mg-c3-sheen,.mg-cover3d:focus-visible .mg-c3-sheen{background-position:0 0}
@media (prefers-reduced-motion:no-preference){
  .mg-c3-book{animation:mg-rise 1.2s var(--ez) both}
  @keyframes mg-rise{from{opacity:0;transform:rotateY(-28deg) rotateX(8deg) translateY(24px)}}
}

/* ----------------------------------------------------------------- stage */
.mg-stage{position:relative;isolation:isolate;overflow:hidden;padding:0;background:var(--mg-desk);color:var(--fg-on-dark);scroll-margin-top:var(--mg-nav,60px)}
.mg-stage-bg{position:absolute;inset:0;z-index:-1;pointer-events:none;
  background:
    radial-gradient(48% 46% at 50% 44%,rgba(255,150,119,.20),rgba(255,119,89,.07) 45%,rgba(255,119,89,0) 72%),
    radial-gradient(120% 80% at 50% 115%,rgba(255,196,174,.10),transparent 60%),
    linear-gradient(180deg,#0E0E10 0%,#151517 55%,#0E0E10 100%)}
/* Film grain + vignette: the "depth" around the book. */
.mg-stage-bg::before{content:"";position:absolute;inset:0;opacity:.18;mix-blend-mode:overlay;
  background-image:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='160' height='160'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='.85' numOctaves='2' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E")}
.mg-stage-bg::after{content:"";position:absolute;inset:0;background:radial-gradient(110% 85% at 50% 45%,transparent 55%,rgba(0,0,0,.6) 100%)}
.mg-stage-in{position:relative;display:flex;flex-direction:column;align-items:center;justify-content:center;padding:24px var(--pad) 28px;min-height:calc(100vh - var(--mg-nav,60px))}
.mg-hint{margin:0 0 22px;font:500 11px/1 var(--font-mono);letter-spacing:.08em;text-transform:uppercase;color:var(--fg-on-dark-2);opacity:.8;transition:opacity .6s}
.mg-hint.gone{opacity:0}

.mg-desk{position:relative;display:flex;align-items:center;justify-content:center;width:100%}
.mg-holder{position:relative;margin:0 auto;width:min(100%,1000px)}
.mg-book{position:relative;z-index:1;margin:0 auto}
.js .mg-book:not(.ready){visibility:hidden}
/* Pages */
.mg-page{position:relative;background:#F7F4EE;overflow:hidden;user-select:none;-webkit-user-select:none}
.mg-page img{display:block;width:100%;height:100%;object-fit:cover;background:#ECE8DF;pointer-events:none}
/* Spine crease and the light falling across each page. */
.mg-fold{position:absolute;inset:0;pointer-events:none}
.mg-l .mg-fold{background:linear-gradient(270deg,rgba(0,0,0,.22) 0%,rgba(0,0,0,.08) 2.5%,rgba(0,0,0,0) 7%),linear-gradient(90deg,rgba(255,255,255,.05),rgba(255,255,255,0) 20%)}
.mg-r .mg-fold{background:linear-gradient(90deg,rgba(0,0,0,.24) 0%,rgba(0,0,0,.09) 2.5%,rgba(255,255,255,.05) 5%,rgba(0,0,0,0) 9%),linear-gradient(270deg,rgba(0,0,0,.05),rgba(0,0,0,0) 18%)}
.mg-c .mg-fold{background:linear-gradient(90deg,rgba(0,0,0,.18),rgba(255,255,255,.07) 2%,rgba(0,0,0,0) 6%)}
.mg-book.portrait .mg-l .mg-fold{background:linear-gradient(90deg,rgba(0,0,0,.18),rgba(0,0,0,0) 6%)}
/* The book's shadow on the desk, plus a stack of page edges under it. */
.mg-floor{position:absolute;left:4%;right:4%;bottom:-26px;height:46px;border-radius:50%;background:radial-gradient(closest-side,rgba(0,0,0,.75),rgba(0,0,0,0));filter:blur(10px);z-index:0;pointer-events:none}
.mg-book .stf__block{filter:drop-shadow(0 22px 26px rgba(0,0,0,.45)) drop-shadow(0 2px 3px rgba(0,0,0,.35))}
@media (max-width:760px){.mg-book .stf__block{filter:drop-shadow(0 14px 16px rgba(0,0,0,.45))}}

/* Big side arrows (desktop) */
.mg-arrow{position:absolute;top:50%;z-index:3;display:grid;place-items:center;width:56px;height:56px;margin-top:-28px;border-radius:50%;border:1px solid rgba(244,242,236,.16);background:rgba(27,27,31,.55);color:var(--fg-on-dark);cursor:pointer;backdrop-filter:blur(8px);-webkit-backdrop-filter:blur(8px);transition:background .25s,border-color .25s,opacity .25s,transform .25s var(--ez)}
.mg-arrow svg{width:22px;height:22px}
.mg-arrow.prev{left:0}.mg-arrow.next{right:0}
.mg-arrow:hover{background:rgba(255,119,89,.9);border-color:transparent;color:var(--bt-ink)}
.mg-arrow:active{transform:scale(.94)}
.mg-arrow[disabled]{opacity:0;pointer-events:none}

/* Toolbar */
.mg-bar{position:relative;display:flex;align-items:center;gap:4px;margin-top:40px;padding:6px;border-radius:999px;background:rgba(27,27,31,.72);border:1px solid rgba(244,242,236,.1);box-shadow:0 20px 40px -20px rgba(0,0,0,.8);backdrop-filter:blur(12px);-webkit-backdrop-filter:blur(12px)}
.mg-b{display:grid;place-items:center;width:42px;height:42px;border-radius:50%;border:0;background:transparent;color:var(--fg-on-dark);cursor:pointer;text-decoration:none;transition:background .2s,color .2s}
.mg-b svg{width:19px;height:19px}
.mg-b:hover{background:rgba(244,242,236,.1)}
.mg-b[aria-expanded="true"]{background:var(--c02-sun-5);color:var(--bt-ink)}
.mg-b[disabled]{opacity:.3;pointer-events:none}
.mg-fs .off,.mg-stage.is-fs .mg-fs .on{display:none}.mg-stage.is-fs .mg-fs .off{display:block}
.mg-count{display:flex;align-items:baseline;gap:6px;min-width:128px;justify-content:center;margin:0 6px;font:500 13px/1 var(--font-mono);letter-spacing:.06em;color:var(--fg-on-dark);white-space:nowrap}
.mg-of{color:var(--fg-on-dark-2)}
.mg-sep{width:1px;height:22px;margin:0 6px;background:rgba(244,242,236,.14)}
.mg-prog{position:absolute;left:22px;right:22px;bottom:-1px;height:2px;border-radius:2px;overflow:hidden;background:rgba(244,242,236,.06)}
.mg-prog i{display:block;height:100%;width:0;background:linear-gradient(90deg,var(--c02-sun-3),var(--c02-sun-5));transition:width .6s var(--ez)}
:focus-visible{outline:2px solid var(--c02-sun-4);outline-offset:3px}

/* Page strip */
.mg-thumbs{width:100%;max-width:1200px;margin-top:22px}
.mg-thumbs ol{list-style:none;display:flex;gap:10px;margin:0;padding:6px 4px 14px;overflow-x:auto;scroll-snap-type:x proximity;scrollbar-width:thin;scrollbar-color:rgba(244,242,236,.25) transparent}
.mg-thumbs li{flex:none;scroll-snap-align:center}
.mg-th{display:flex;flex-direction:column;align-items:center;gap:8px;padding:0;border:0;background:none;color:var(--fg-on-dark-2);cursor:pointer;font:500 11px/1 var(--font-mono);letter-spacing:.06em}
.mg-th img{display:block;width:72px;height:auto;border-radius:3px;opacity:.6;outline:2px solid transparent;outline-offset:2px;transition:opacity .2s,outline-color .2s,transform .25s var(--ez)}
.mg-th:hover img{opacity:1;transform:translateY(-3px)}
.mg-th.on{color:var(--fg-on-dark)}
.mg-th.on img{opacity:1;outline-color:var(--c02-sun-5)}
.mg-nojs{color:var(--fg-on-dark-2)}.mg-nojs a{color:var(--fg-on-dark)}

/* Full screen: the stage becomes the whole screen. */
.mg-stage.is-fs .mg-stage-in{min-height:100vh;padding-top:16px;padding-bottom:20px}
.mg-stage.is-fs .mg-hint{display:none}
.mg-stage.is-fs .mg-bar{margin-top:28px}

/* --------------------------------------------------------------- contents */
.mg-inside{padding:112px 0;background:var(--bt-paper)}
.mg-head{max-width:760px}
.mg-head h2{margin:18px 0 14px}
.mg-sub{margin:0;color:var(--bt-concrete-700);font-size:17px}
.mg-group{margin:64px 0 20px;font:500 13px/1 var(--font-mono);letter-spacing:.08em;text-transform:uppercase;color:var(--bt-concrete-500);padding-bottom:16px;border-bottom:var(--hair)}
.mg-grid{list-style:none;margin:0;padding:0;display:grid;grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:16px}
.mg-grid-4{grid-template-columns:repeat(4,minmax(0,1fr))}
.mg-grid-2{grid-template-columns:repeat(2,minmax(0,1fr))}
.mg-card a{display:grid;grid-template-columns:72px minmax(0,1fr);gap:18px;align-items:center;height:100%;padding:14px 18px 14px 14px;border-radius:var(--r-md);background:var(--bt-white);border:1px solid var(--bt-concrete-100);color:var(--bt-ink);text-decoration:none;transition:transform .35s var(--ez),box-shadow .35s var(--ez),border-color .35s var(--ez)}
.mg-card a:hover{transform:translateY(-3px);border-color:rgba(255,150,119,.55);box-shadow:0 24px 40px -28px rgba(196,72,40,.45)}
.mg-cimg{display:block;border-radius:4px;overflow:hidden;box-shadow:0 1px 0 rgba(11,11,12,.06),0 8px 16px -10px rgba(11,11,12,.4)}
.mg-cimg img{display:block;width:100%;height:auto}
.mg-ctxt{display:flex;flex-direction:column;gap:8px;min-width:0}
.mg-ck{display:flex;align-items:center;gap:8px;font:500 11px/1.2 var(--font-mono);letter-spacing:.08em;text-transform:uppercase;color:var(--bt-concrete-500)}
.mg-cn{color:var(--c02-sun-5)}
.mg-ct{font:400 18px/1.25 var(--font-head);letter-spacing:-.02em;text-wrap:balance}
.mg-cp{font:500 11px/1 var(--font-mono);letter-spacing:.06em;color:var(--bt-concrete-500)}

/* ------------------------------------------------------------------- next */
.mg-next{padding:0 0 112px;background:var(--bt-paper)}
.mg-next-card{position:relative;overflow:hidden;display:grid;grid-template-columns:minmax(0,1fr) auto;gap:48px;align-items:end;padding:72px;border-radius:var(--r-lg);background:var(--c02-sun)}
.mg-next-card h2{margin:16px 0 16px;max-width:18ch}
.mg-next-card p{margin:0;max-width:52ch;font-size:18px;line-height:1.55;color:var(--bt-ink)}
.mg-next-card .lbl{color:var(--bt-ink)}
.mg-next-a{display:flex;flex-direction:column;align-items:flex-start;gap:16px}
.mg-next-a .tlink{color:var(--bt-ink);font-size:15px}

/* ------------------------------------------------------------------- zoom */
.mg-zoom{width:100vw;height:100vh;max-width:none;max-height:none;margin:0;padding:0;border:0;background:rgba(10,10,12,.96);color:var(--fg-on-dark)}
.mg-zoom::backdrop{background:rgba(0,0,0,.6)}
.mg-zoom[open]{display:flex;flex-direction:column}
.mg-zoom-bar{display:flex;align-items:center;justify-content:space-between;gap:16px;padding:10px 16px 10px 24px;border-bottom:1px solid rgba(244,242,236,.08)}
.mg-zoom-t{margin:0;font:500 12px/1 var(--font-mono);letter-spacing:.08em;text-transform:uppercase;color:var(--fg-on-dark-2)}
.mg-zoom-body{flex:1;overflow:auto;display:flex;justify-content:center;align-items:flex-start;gap:0;padding:24px;overscroll-behavior:contain}
.mg-zoom-body img{display:block;width:min(100%,900px);height:auto;background:#ECE8DF}
.mg-zoom-body.two img{width:min(50%,900px)}

/* -------------------------------------------------------------- responsive */
@media (max-width:1100px){
  .mg-hero-in{grid-template-columns:1fr;gap:56px;padding-top:56px;padding-bottom:88px}
  .mg-cover3d{width:min(70%,360px)}
  .mg-grid-4{grid-template-columns:repeat(2,minmax(0,1fr))}
  .mg-next-card{grid-template-columns:1fr;padding:48px}
}
@media (max-width:900px){.mg-arrow{display:none}}
@media (max-width:760px){
  .mg-hero-in{padding-top:28px;padding-bottom:56px;gap:40px}
  .mg-hero h1{margin:16px 0 18px}
  .mg-lead{font-size:16px}
  .mg-facts{gap:28px;margin-top:24px;padding-top:18px}.mg-facts b{font-size:34px}
  .mg-ctas{margin-top:26px}
  .mg-ctas .btn{flex:1 1 100%}
  .mg-cover3d{width:min(60%,260px)}
  .mg-c3-book{transform:rotateY(-12deg) rotateX(3deg)}
  .mg-stage-in{padding:16px 12px 24px}
  .mg-inside{padding:72px 0}.mg-next{padding-bottom:72px}
  .mg-hint{margin-bottom:14px;font-size:10.5px;letter-spacing:.06em;text-align:center}
  .mg-hint .mg-k{min-width:20px;height:20px;margin:0 1px;vertical-align:-5px}
  .mg-bar{margin-top:26px;gap:0;padding:4px}
  .mg-b{width:44px;height:44px}
  .mg-count{min-width:78px;font-size:12px;margin:0 2px}
  .mg-sep{margin:0 2px}
  .mg-b[data-mg-first],.mg-bar .mg-b[data-mg-download]{display:none}
  .mg-prog{left:16px;right:16px}
  .mg-grid,.mg-grid-4,.mg-grid-2{grid-template-columns:1fr}
  .mg-next-card{padding:32px 24px;gap:28px}
  .mg-next-a{width:100%}.mg-next-a .btn{width:100%}
  .mg-zoom-body{padding:0}
  .mg-zoom-body.two{flex-direction:column}
  .mg-zoom-body.two img,.mg-zoom-body img{width:100%}
}
/* Phones without the full screen API: the stage covers the window. */
.mg-stage.is-fs.pseudo{position:fixed;inset:0;z-index:200;overflow:auto}
/* A closed book sits in the middle of the desk, not off to one side. */
.mg-book{transition:transform .7s var(--ez)}
.mg-holder.at-front .mg-book{transform:translateX(-25%)}
.mg-holder.at-back .mg-book{transform:translateX(25%)}
.mg-holder.at-front .mg-floor{left:30%;right:4%}
.mg-holder.at-back .mg-floor{left:4%;right:30%}
.mg-floor{transition:left .7s var(--ez),right .7s var(--ez)}
@media (prefers-reduced-motion:reduce){.mg-book,.mg-floor{transition:none}}
@media (max-width:359px){
  .mg-b{width:40px;height:40px}
  .mg-count{min-width:70px;font-size:11px}
  .mg-sep{display:none}
}
/* Staff preview of a version that may not be live (/magazine?v=<id>). */
.mg-preview{margin:0 0 14px;padding:7px 14px;border-radius:999px;background:rgba(255,119,89,.16);border:1px solid rgba(255,150,119,.4);color:var(--c02-sun-3);font:500 11px/1.3 var(--font-mono);letter-spacing:.06em;text-transform:uppercase;text-align:center}