/* ============================================================
   Design Systems Academy: Material 3, docs style.
   Modeled on material.io / material-web.dev: light, plain, content-first.
   Minimal custom CSS; official --md-sys-* light tokens; real md-* components.
   ============================================================ */
:root{
  --md-sys-color-primary:#415f91; --md-sys-color-on-primary:#ffffff;
  --md-sys-color-primary-container:#d6e3ff; --md-sys-color-on-primary-container:#001b3e;
  --md-sys-color-secondary:#565f71; --md-sys-color-on-secondary:#ffffff;
  --md-sys-color-secondary-container:#dae2f9; --md-sys-color-on-secondary-container:#3e4759;
  --md-sys-color-tertiary:#705575; --md-sys-color-tertiary-container:#fad8fd; --md-sys-color-on-tertiary-container:#583e5e;
  --md-sys-color-error:#ba1a1a; --md-sys-color-error-container:#ffdad6; --md-sys-color-on-error-container:#410002;
  --md-sys-color-surface:#f9f9ff; --md-sys-color-on-surface:#191c20;
  --md-sys-color-surface-variant:#e0e2ec; --md-sys-color-on-surface-variant:#43474e;
  --md-sys-color-surface-container-lowest:#ffffff; --md-sys-color-surface-container-low:#f3f3fa;
  --md-sys-color-surface-container:#edeef4; --md-sys-color-surface-container-high:#e7e8ee;
  --md-sys-color-surface-container-highest:#e2e2e9;
  --md-sys-color-outline:#73777f; --md-sys-color-outline-variant:#c3c6cf;
  --md-sys-color-success:#146c2e; --md-sys-color-success-container:#c7f0cd;
}
*{box-sizing:border-box}
html,body{background:var(--md-sys-color-surface)}
body{margin:0;font-family:"Roboto",system-ui,sans-serif;font-size:16px;line-height:1.7;
  color:var(--md-sys-color-on-surface);-webkit-font-smoothing:antialiased}
a{color:var(--md-sys-color-primary)}
img,svg{max-width:100%;height:auto}
code{font-family:"Roboto Mono",ui-monospace,monospace;font-size:.875em;
  background:var(--md-sys-color-surface-container);padding:.12em .4em;border-radius:4px}
.material-symbols-outlined{font-family:'Material Symbols Outlined';font-weight:normal;font-size:20px;line-height:1;display:inline-block;-webkit-font-feature-settings:'liga'}

/* layout: fixed drawer + content, like docs */
.app{display:grid;grid-template-columns:256px 1fr;min-height:100vh}
.sidebar{position:sticky;top:0;height:100vh;overflow-y:auto;
  border-right:1px solid var(--md-sys-color-outline-variant);padding:16px 8px}
a.brand,.brand{text-decoration:none;color:inherit}
.brand{display:flex;align-items:center;gap:10px;margin:6px 12px 2px}
/*logo*/
.brand .mark img{width:20px;height:20px;display:block}
.brand .mark{width:32px;height:32px;border-radius:8px;background:var(--md-sys-color-primary-container);display:grid;place-items:center}
.brand .name{font-weight:500;font-size:14px;line-height:1.25}
.brand .name small{display:block;font-weight:400;color:var(--md-sys-color-on-surface-variant);font-size:11px}
.sidebar md-linear-progress{margin:14px 12px 2px}
.plabel{font-size:11px;color:var(--md-sys-color-on-surface-variant);margin:0 12px 8px}
.toc-h{font-size:11px;letter-spacing:.06em;text-transform:uppercase;color:var(--md-sys-color-on-surface-variant);
  font-weight:500;margin:16px 0 2px 16px}
.sidebar md-list{--md-list-container-color:transparent;padding:0}
.sidebar md-list-item{border-radius:0 99px 99px 0;
  --md-list-item-top-space:6px;--md-list-item-bottom-space:6px;--md-list-item-leading-space:16px;
  --md-list-item-label-text-size:14px;--md-list-item-label-text-color:var(--md-sys-color-on-surface-variant)}
.sidebar md-list-item.active{background:var(--md-sys-color-secondary-container);
  --md-list-item-label-text-color:var(--md-sys-color-on-secondary-container);--md-list-item-label-text-weight:500}
.sidebar md-list-item .n{color:var(--md-sys-color-on-surface-variant);font-size:12px;min-width:22px}
.sidebar md-list-item.active .n{color:var(--md-sys-color-on-secondary-container)}

.topbar{position:sticky;top:0;z-index:5;height:56px;display:flex;justify-content:space-between;align-items:center;
  padding:0 24px;background:var(--md-sys-color-surface);border-bottom:1px solid var(--md-sys-color-outline-variant)}
.crumbs{font-size:13.5px;color:var(--md-sys-color-on-surface-variant)}
.crumbs b{color:var(--md-sys-color-on-surface);font-weight:500}
.navbtns{display:flex;gap:8px;align-items:center}
.wrap{max-width:44rem;margin:0 auto;padding:40px 32px 120px}

/* content: plain docs typography */
.hero .kicker{font-size:12px;letter-spacing:.4px;text-transform:uppercase;color:var(--md-sys-color-primary);font-weight:500}
.hero h1{font-weight:400;font-size:2.5rem;line-height:1.18;margin:10px 0 10px}
.hero .lede{font-size:1.22rem;line-height:1.5;color:var(--md-sys-color-on-surface-variant);margin:0}
.hero .meta{display:flex;gap:8px;flex-wrap:wrap;margin-top:20px}
.heroart{margin:32px 0 4px;padding:28px;display:grid;place-items:center;
  background:var(--md-sys-color-surface-container-low);border-radius:12px}
.heroart img{max-height:200px}
md-elevated-card.heroart{--md-elevated-card-container-color:var(--md-sys-color-surface-container-low)}

.prose{margin-top:12px}
.prose h2{font-weight:400;font-size:1.55rem;line-height:1.3;margin:2.6rem 0 .8rem;
  padding-bottom:.4rem;border-bottom:1px solid var(--md-sys-color-outline-variant)}
.prose h3{font-weight:500;font-size:1.18rem;margin:1.8rem 0 .5rem}
.prose p{margin:0 0 1.2rem}
.prose strong{font-weight:500}
.prose ul,.prose ol{margin:0 0 1.2rem;padding-left:1.4rem}
.prose li{margin:.4rem 0}

/* quote: plain docs blockquote, left rule */
md-elevated-card.quote,.quote{display:block;margin:1.6rem 0;padding:4px 0 4px 20px;
  border-left:3px solid var(--md-sys-color-primary);background:transparent;box-shadow:none;
  --md-elevated-card-container-color:transparent;--md-elevated-card-container-elevation:0}
.quote p{font-size:1.05rem;line-height:1.6;color:var(--md-sys-color-on-surface);font-style:italic;margin:0 0 .5rem}
.quote cite{display:block;font-style:normal;font-weight:500;color:var(--md-sys-color-on-surface-variant);font-size:.85rem}
.quote cite small{display:block;color:var(--md-sys-color-on-surface-variant);font-weight:400;opacity:.8;margin-top:1px}

/* note / callout: Material docs "note" box */
.callout{margin:1.6rem 0;padding:14px 18px;border-radius:8px;display:flex;gap:12px;
  background:var(--md-sys-color-surface-container-low);border-left:4px solid var(--md-sys-color-primary)}
.callout .ic{flex:0 0 24px;height:24px;color:var(--md-sys-color-primary);display:grid;place-items:center}
.callout p{margin:0;font-size:.95rem}
.pitfalls{margin:1.6rem 0;padding:16px 20px;border-radius:8px;
  background:var(--md-sys-color-surface-container-low);border-left:4px solid var(--md-sys-color-error)}
.pitfalls h4{margin:0 0 8px;font-size:.95rem;font-weight:500;display:flex;gap:8px;align-items:center}
.pitfalls h4 .x{color:var(--md-sys-color-error)}
.pitfalls ul{margin:0;padding-left:1.2rem}.pitfalls li{margin:.4rem 0}
.takeaway{margin:2rem 0;padding:16px 20px;border-radius:8px;
  background:var(--md-sys-color-surface-container-low);border-left:4px solid var(--md-sys-color-primary)}
.takeaway .t{font-size:11px;letter-spacing:.4px;text-transform:uppercase;font-weight:500;color:var(--md-sys-color-primary)}
.takeaway p{margin:.3rem 0 0;font-size:1.05rem;line-height:1.5;color:var(--md-sys-color-on-surface)}

figure{margin:2rem 0}
.prose figure img{cursor:zoom-in}
.prose figure .frame:hover{border-color:var(--md-sys-color-primary)}
/* lightbox: kept out of the render tree while closed so it never repaints on scroll */
.lb-scrim{position:fixed;inset:0;z-index:1000;background:rgba(10,14,20,.9);flex-direction:column;
  align-items:center;justify-content:center;gap:14px;padding:32px;display:none}
.lb-scrim.open{display:flex}
.lb-scrim img{max-width:96vw;max-height:82vh;border-radius:10px;box-shadow:0 24px 80px rgba(0,0,0,.5);cursor:zoom-out}
.lb-cap{color:#e9edf5;font-size:13.5px;max-width:60rem;text-align:center}
.lb-close{position:absolute;top:18px;right:22px;color:#fff;font-size:30px;line-height:1;cursor:pointer;
  width:44px;height:44px;display:grid;place-items:center;border-radius:50%;background:rgba(255,255,255,.12)}
.lb-close:hover{background:rgba(255,255,255,.22)}
figure .frame{border-radius:8px;overflow:hidden;background:#fff;border:1px solid var(--md-sys-color-outline-variant)}
figure .frame.dark{background:#0e121a}
figure .frame img{display:block;width:100%}
figure figcaption{margin-top:8px;font-size:12.5px;color:var(--md-sys-color-on-surface-variant);text-align:center}

/* tables: plain docs table */
md-outlined-card.compare,.compare{display:block;margin:1.6rem 0;overflow-x:auto;
  border:1px solid var(--md-sys-color-outline-variant);border-radius:8px;--md-outlined-card-container-color:transparent}
.compare table{border-collapse:collapse;width:100%;font-size:14px;table-layout:fixed}
.compare th,.compare td{text-align:left;padding:12px 16px;border-bottom:1px solid var(--md-sys-color-outline-variant);vertical-align:top}
.compare thead th{color:var(--md-sys-color-on-surface);font-weight:500;font-size:13px;background:var(--md-sys-color-surface-container-low)}
.compare tbody tr:last-child td{border-bottom:0}
.compare td:first-child{font-weight:500}

.video{margin:2rem 0}
.video .box{position:relative;padding-top:56.25%;border-radius:8px;overflow:hidden;background:#000}
.video iframe{position:absolute;inset:0;width:100%;height:100%;border:0}
.video .cap{margin-top:8px;font-size:12.5px;color:var(--md-sys-color-on-surface-variant)}

/* quiz: plain bordered block with md-radio */
md-elevated-card.quiz,.quiz{display:block;margin:2.4rem 0;overflow:hidden;border-radius:12px;
  border:1px solid var(--md-sys-color-outline-variant);box-shadow:none;
  --md-elevated-card-container-color:transparent;--md-elevated-card-container-elevation:0}
.quiz .head{padding:16px 20px;border-bottom:1px solid var(--md-sys-color-outline-variant);display:flex;align-items:center;gap:12px}
.quiz .head .ic{color:var(--md-sys-color-primary);display:grid;place-items:center}
.quiz .head b{font-weight:500}
.quiz .head span{color:var(--md-sys-color-on-surface-variant);font-size:13px}
.quiz .q{padding:18px 20px;border-top:1px solid var(--md-sys-color-outline-variant)}
.quiz .q:first-of-type{border-top:0}
.quiz .q .ask{font-weight:500;margin:0 0 8px}
.quiz .opt{display:flex;gap:10px;align-items:center;padding:8px 8px;border-radius:8px;margin:2px 0;cursor:pointer;font-size:14.5px}
.quiz .opt:hover{background:var(--md-sys-color-surface-container-low)}
.quiz .opt.correct{background:var(--md-sys-color-success-container)}
.quiz .opt.wrong{background:var(--md-sys-color-error-container)}
.quiz .exp{display:none;margin:0 0 6px 34px;font-size:13px;color:var(--md-sys-color-on-surface-variant)}
.quiz .exp.show{display:block}
.quiz .foot{padding:12px 20px;display:flex;justify-content:space-between;align-items:center;
  border-top:1px solid var(--md-sys-color-outline-variant)}
.quiz .score{font-weight:500;font-size:14px}
.quiz .foot .hint{color:var(--md-sys-color-on-surface-variant);font-size:13px}

.footnav{max-width:44rem;margin:0 auto;padding:0 32px 80px;display:flex;justify-content:space-between;gap:12px}
.footnav a{flex:1;border-radius:8px;padding:14px 16px;border:1px solid var(--md-sys-color-outline-variant)}
.footnav a:hover{background:var(--md-sys-color-surface-container-low)}
.footnav .dir{font-size:12px;color:var(--md-sys-color-on-surface-variant)}
.footnav .ttl{color:var(--md-sys-color-on-surface);font-weight:500;font-size:14px;margin-top:2px}
.footnav a.next{text-align:right}

@media(max-width:900px){.app{grid-template-columns:1fr}.sidebar{display:none}.wrap{padding:32px 20px 80px}}

/* lightweight youtube facade (loads player only on click) */
.video .box .lite-yt{position:absolute;inset:0;width:100%;height:100%;border:0;padding:0;cursor:pointer;
  background-size:cover;background-position:center;background-color:#000;display:grid;place-items:center}
.video .box .lite-yt::after{content:"";position:absolute;inset:0;background:rgba(0,0,0,.18)}
.lite-play{position:relative;z-index:1;width:68px;height:48px;border-radius:12px;background:#f00;box-shadow:0 2px 8px rgba(0,0,0,.35)}
.lite-play::before{content:"";position:absolute;top:50%;left:50%;transform:translate(-40%,-50%);
  border-style:solid;border-width:11px 0 11px 19px;border-color:transparent transparent transparent #fff}
.video .box .lite-yt:hover .lite-play{background:#ff2626}