:root{
  --paper:#f5f2ee; --surface:#fff; --ink:#2a2320; --muted:#736a62;
  --line:#e7e1d8; --brand:#ef6a33; --brand-soft:#fdeadf; --green:#1f9d57; --green-soft:#e4f3ea;
  --pine:#1f7a46; --amber:#e0a63a;
  --shadow:0 1px 2px rgba(42,35,32,.05),0 8px 24px rgba(42,35,32,.07);
  --disp:"Be Vietnam Pro",system-ui,sans-serif; --body:"Be Vietnam Pro",system-ui,sans-serif;
  color-scheme:light;
}
@media (prefers-color-scheme:dark){:root:not([data-theme="light"]){
  --paper:#191512; --surface:#231d19; --ink:#efe9e3; --muted:#a79d93;
  --line:#39302a; --brand:#f5824f; --brand-soft:#2d211a; --green:#4cc585; --green-soft:#1b2a20;
  --pine:#4cc585; --amber:#e3b155; color-scheme:dark;
}}
:root[data-theme="dark"]{
  --paper:#191512; --surface:#231d19; --ink:#efe9e3; --muted:#a79d93;
  --line:#39302a; --brand:#f5824f; --brand-soft:#2d211a; --green:#4cc585; --green-soft:#1b2a20;
  --pine:#4cc585; --amber:#e3b155; color-scheme:dark;
}
*{box-sizing:border-box}
html,body{margin:0}
body{background:var(--paper);color:var(--ink);font-family:var(--body);line-height:1.65;-webkit-font-smoothing:antialiased}
h1,h2,h3,h4{font-family:var(--disp);font-weight:700;line-height:1.2;margin:0;text-wrap:balance}
a{color:var(--brand);text-decoration:none}
img{max-width:100%;height:auto}
.btn{display:inline-flex;align-items:center;gap:.5em;background:var(--brand);color:#fff;border:none;border-radius:999px;padding:.7em 1.3em;font-weight:600;font-size:.95rem;cursor:pointer;font-family:inherit}
.btn.ghost{background:transparent;color:var(--brand);border:1.5px solid var(--line)}
.eyebrow{font-size:.74rem;letter-spacing:.14em;text-transform:uppercase;color:var(--brand);font-weight:700}
.wrap{width:100%;max-width:1180px;margin-inline:auto;padding-left:max(18px,env(safe-area-inset-left,0px));padding-right:max(18px,env(safe-area-inset-right,0px))}
:focus-visible{outline:2.5px solid var(--brand);outline-offset:2px;border-radius:6px}

/* ---------- ACADEMY HOME ---------- */
.top{position:sticky;top:0;z-index:20;background:color-mix(in srgb,var(--paper) 90%,transparent);backdrop-filter:blur(8px);border-bottom:1px solid var(--line)}
.top .wrap{display:flex;align-items:center;justify-content:space-between;padding-block:.8rem}
.brand{display:flex;align-items:center;gap:.6rem;font-family:var(--disp);font-weight:700;font-size:1.15rem;color:var(--ink)}
.brand .seal{width:32px;height:32px;border-radius:9px;background:var(--brand);color:#fff;display:grid;place-items:center}
.tg{background:transparent;border:1.5px solid var(--line);color:var(--muted);border-radius:999px;width:38px;height:38px;cursor:pointer;font-size:1rem}
.hero{padding-block:clamp(2.4rem,6vw,4.4rem)}
.hero h1{font-size:clamp(2.1rem,5vw,3.4rem);letter-spacing:-.01em}
.hero .lede{font-size:1.12rem;color:var(--muted);margin-top:1rem;max-width:52ch}
.hero .stats{display:flex;gap:2rem;margin-top:1.8rem;flex-wrap:wrap}
.hero .stats .s b{font-family:var(--disp);font-size:1.7rem;color:var(--brand);display:block}
.hero .stats .s span{font-size:.85rem;color:var(--muted)}
.track{padding-block:1.6rem}
.track-h{display:flex;align-items:baseline;gap:.8rem;margin-bottom:1.2rem;flex-wrap:wrap}
.track-h h2{font-size:clamp(1.4rem,3vw,1.9rem)}
.track-h span{color:var(--muted);font-size:.9rem}
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:1.1rem}
.cc{display:flex;flex-direction:column;background:var(--surface);border:1px solid var(--line);border-radius:14px;overflow:hidden;box-shadow:var(--shadow);color:var(--ink);transition:border-color .15s,transform .08s}
.cc:hover{border-color:var(--brand);transform:translateY(-2px)}
.thumb{aspect-ratio:16/9;background-size:cover;background-position:center;position:relative;overflow:hidden}
.thumb img{width:100%;height:100%;object-fit:cover;display:block}
.cc-b{display:flex;flex-direction:column;gap:.45rem;padding:1.1rem 1.2rem;flex:1}
.cc .code{font-size:.72rem;font-weight:700;letter-spacing:.08em;color:var(--muted)}
.cc h3{font-size:1.1rem}
.cc .m{font-size:.82rem;color:var(--muted);margin-top:auto}
.cc .go{color:var(--brand);font-weight:600;font-size:.88rem;margin-top:.3rem}
.feat{border:none;grid-column:span 2}
.feat .cc-b{background:linear-gradient(150deg,var(--pine),#123f27)}
.feat .code,.feat .m{color:rgba(255,255,255,.85)}
.feat h3{color:#fff;font-size:1.35rem}
.feat .go{color:#fff}
.feat p{color:rgba(255,255,255,.92);font-size:.9rem;margin:0}
@media (max-width:620px){.feat{grid-column:auto}}

/* hero with image */
.hero-img{position:relative;overflow:hidden;background-size:cover;background-position:center;min-height:clamp(340px,52vw,480px);display:flex;align-items:flex-end}
.hero-bg{position:absolute;inset:0;width:100%;height:100%;object-fit:cover;z-index:0}
.hero-ov{position:relative;z-index:1;width:100%;padding-block:clamp(2rem,5vw,3.4rem);background:linear-gradient(to top,rgba(10,8,6,.86),rgba(10,8,6,.48) 55%,rgba(10,8,6,.15))}
.hero-ov h1{color:#fff;font-size:clamp(2rem,5vw,3.3rem);letter-spacing:-.01em;max-width:18ch}
.hero-ov .lede{color:rgba(255,255,255,.92);font-size:1.1rem;margin-top:1rem;max-width:50ch}
.hero-ov .stats .s b{color:#ffb98c}
.hero-ov .stats .s span{color:rgba(255,255,255,.8)}

/* course banner */
.cover.banner{aspect-ratio:21/7;max-height:260px;background-size:cover;background-position:center;border-radius:14px;overflow:hidden;margin-bottom:1.5rem}
.cover.banner img{width:100%;height:100%;object-fit:cover;display:block}
.note{background:var(--brand-soft);border:1px solid var(--line);border-left:3px solid var(--amber);border-radius:10px;padding:.8rem 1rem;font-size:.85rem;color:var(--muted);margin-top:1.4rem}
.foot{border-top:1px solid var(--line);padding-block:1.6rem;color:var(--muted);font-size:.85rem;margin-top:2rem}

/* ---------- READER ---------- */
.reader{background:var(--paper)}
.rbar{position:sticky;top:0;z-index:30;display:flex;align-items:center;gap:1rem;background:var(--surface);border-bottom:1px solid var(--line);padding:.7rem max(16px,env(safe-area-inset-left,0px))}
.rbar .back{font-weight:600;color:var(--brand);white-space:nowrap}
.rbar-t{flex:1;min-width:0;font-weight:600;overflow:hidden;text-overflow:ellipsis;white-space:nowrap;color:var(--ink)}
.rwrap{display:grid;grid-template-columns:280px 1fr;max-width:1180px;margin-inline:auto;gap:0}
.toc{position:sticky;top:56px;align-self:start;height:calc(100vh - 56px);overflow-y:auto;border-right:1px solid var(--line);padding:1.2rem 1rem;background:var(--surface)}
.toc-h{font-size:.74rem;letter-spacing:.1em;text-transform:uppercase;color:var(--muted);font-weight:700;margin-bottom:.7rem}
.toc nav{display:flex;flex-direction:column;gap:.1rem}
.toc nav a{color:var(--muted);font-size:.86rem;padding:.4rem .5rem;border-radius:8px;line-height:1.35}
.toc nav a:hover{background:var(--paper);color:var(--ink)}
.rmain{min-width:0;padding:clamp(1.3rem,3vw,2.6rem);max-width:820px}
.course-head{border-bottom:1px solid var(--line);padding-bottom:1.3rem;margin-bottom:1.4rem}
.course-head h1{font-size:clamp(1.7rem,4vw,2.4rem);margin-top:.4rem}
.course-head .meta{color:var(--muted);font-size:.9rem;margin-top:.6rem;font-weight:600}
.refnote{font-size:.84rem;color:var(--muted);margin-top:.8rem;background:var(--brand-soft);border-radius:8px;padding:.6rem .8rem}
.toc-m{display:none;margin-bottom:1.4rem;border:1px solid var(--line);border-radius:10px;padding:.4rem .8rem;background:var(--surface)}
.toc-m summary{font-weight:600;cursor:pointer;padding:.4rem 0}
.toc-m nav{display:flex;flex-direction:column;gap:.1rem;padding-bottom:.6rem}
.toc-m nav a{color:var(--muted);font-size:.86rem;padding:.3rem .2rem}
.chapter{margin-bottom:2.2rem;scroll-margin-top:70px}
.chapter h2{font-size:1.5rem;color:var(--brand);padding-bottom:.4rem;border-bottom:2px solid var(--brand-soft);margin-bottom:1rem}
.chapter h3{font-size:1.15rem;margin-top:1.6rem}
.chapter h4{font-size:1rem;margin-top:1.2rem;color:var(--pine)}
.chapter p{margin:.7rem 0;max-width:70ch}
.chapter ul{margin:.6rem 0;padding-left:1.3rem}
.chapter li{margin:.3rem 0;max-width:68ch}
.chapter figure{margin:1.2rem 0;text-align:center}
.chapter figure img{border-radius:10px;border:1px solid var(--line)}
.course-foot{margin-top:2.5rem;padding-top:1.4rem;border-top:1px solid var(--line)}

@media (max-width:820px){
  .rwrap{grid-template-columns:1fr}
  .toc{display:none}
  .toc-m{display:block}
  .rmain{max-width:100%}
}
@media (prefers-reduced-motion:reduce){*{transition:none!important}}