:root{
  --paper:#F4F5F8; --card:#FFFFFF; --ink:#1A1D26; --muted:#646B7A; --line:#E4E7EC;
  --accent:#5A4FCF; --accent-soft:#EDEBFB; --accent-ink:#3C348A;
  --teal:#0F6E56; --teal-soft:#E1F5EE;
  --amber:#9A6500; --amber-soft:#FBF1DC;
  --correct:#1E874B; --correct-soft:#E7F4EC;
  --wrong:#C5384B; --wrong-soft:#FBE9EC;
  --mono-bg:#EFF0F4; --mono-ink:#4A4F74;
  --shadow:0 1px 2px rgba(20,24,40,.04), 0 4px 16px rgba(20,24,40,.05);
  --sidebar:300px;
}
@media (prefers-color-scheme: dark){
  :root{
    --paper:#121419; --card:#1C1F27; --ink:#E9EAEF; --muted:#9298A6; --line:#2B2F39;
    --accent:#9D94F0; --accent-soft:#242137; --accent-ink:#CECBF6;
    --teal:#5DCAA5; --teal-soft:#0E2C24;
    --amber:#E0B463; --amber-soft:#2B2410;
    --correct:#54C98A; --correct-soft:#142819; --wrong:#F0939E; --wrong-soft:#2C181C;
    --mono-bg:#252A34; --mono-ink:#B9BEEA;
    --shadow:0 1px 2px rgba(0,0,0,.2), 0 4px 16px rgba(0,0,0,.25);
  }
}
*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{background:var(--paper);color:var(--ink);font-family:"Inter",system-ui,sans-serif;line-height:1.6;-webkit-font-smoothing:antialiased}
code{font-family:"IBM Plex Mono",monospace;font-size:.86em;background:var(--mono-bg);color:var(--mono-ink);padding:2px 6px;border-radius:5px;font-weight:500;word-break:break-word}

/* ---------- layout ---------- */
.app{display:flex;min-height:100vh}
.sidebar{width:var(--sidebar);flex-shrink:0;background:var(--card);border-right:1px solid var(--line);position:sticky;top:0;height:100vh;overflow-y:auto;padding:22px 16px 40px}
.main{flex:1;min-width:0;padding:38px clamp(20px,5vw,64px) 100px;max-width:920px}

.brand{display:flex;align-items:center;gap:10px;padding:0 8px 18px;margin-bottom:8px;border-bottom:1px solid var(--line)}
.brand .logo{font-family:"Space Grotesk",sans-serif;font-weight:700;font-size:15px;width:34px;height:34px;border-radius:9px;background:var(--accent);color:#fff;display:flex;align-items:center;justify-content:center;flex-shrink:0}
.brand .bt{font-family:"Space Grotesk",sans-serif;font-weight:600;font-size:14px;line-height:1.2}
.brand .bs{font-family:"IBM Plex Mono",monospace;font-size:10.5px;color:var(--muted);letter-spacing:.04em}

nav{margin-top:14px}
.nav-item{display:flex;align-items:center;gap:9px;width:100%;text-align:left;background:transparent;border:none;border-radius:9px;padding:9px 10px;cursor:pointer;font:inherit;font-size:14px;color:var(--ink);font-weight:500}
.nav-item:hover{background:var(--accent-soft)}
.nav-item.active{background:var(--accent-soft);color:var(--accent-ink);font-weight:600}
.nav-item .ico{width:18px;flex-shrink:0;color:var(--muted);font-family:"IBM Plex Mono",monospace;font-size:12px;text-align:center}
.nav-item.active .ico{color:var(--accent)}
.nav-group{font-family:"IBM Plex Mono",monospace;font-size:11px;letter-spacing:.06em;text-transform:uppercase;color:var(--muted);padding:16px 12px 6px;display:flex;justify-content:space-between;align-items:center}
.nav-group .w{font-weight:400;opacity:.75}
.nav-topic{padding-left:30px;font-size:13.5px;font-weight:400}
.nav-topic.active{font-weight:600}
.nav-exam{color:var(--accent);font-weight:600;margin-top:2px}
.nav-exam .ico{color:var(--accent)}
.dot{width:7px;height:7px;border-radius:50%;background:var(--line);flex-shrink:0;margin-left:auto;opacity:0}
.nav-item.started .dot{opacity:1;background:var(--amber)}   /* started reading */
.nav-item.done .dot{opacity:1;background:var(--correct)}    /* scenario exam completed */

/* ---------- progress / data tools (sidebar footer) ---------- */
.side-tools{margin-top:22px;padding:14px 10px 0;border-top:1px solid var(--line)}
.side-tools .st-label{font-family:"IBM Plex Mono",monospace;font-size:11px;letter-spacing:.06em;text-transform:uppercase;color:var(--muted);margin-bottom:9px;display:block}
.side-tools .st-stat{font-size:12.5px;color:var(--muted);margin-bottom:10px}
.side-tools .st-stat b{color:var(--ink);font-weight:600}
.side-tools .st-row{display:flex;gap:6px;flex-wrap:wrap}
.mini{font:inherit;font-size:12px;font-weight:500;background:transparent;color:var(--muted);border:1px solid var(--line);border-radius:8px;padding:6px 10px;cursor:pointer}
.mini:hover{border-color:var(--accent);color:var(--accent)}
.mini.danger:hover{border-color:var(--wrong);color:var(--wrong)}
.lang-row{display:flex;gap:6px;flex-wrap:wrap}
.lang-btn{font:inherit;font-family:"IBM Plex Mono",monospace;font-size:11.5px;font-weight:500;background:transparent;color:var(--muted);border:1px solid var(--line);border-radius:8px;padding:5px 9px;cursor:pointer;letter-spacing:.03em}
.lang-btn:hover{border-color:var(--accent);color:var(--accent)}
.lang-btn.on{background:var(--accent-soft);border-color:var(--accent);color:var(--accent-ink);font-weight:600}
.q-en-note{font-size:12.5px;color:var(--muted);font-style:italic;margin-bottom:14px}

/* ---------- content ---------- */
.eyebrow{font-family:"IBM Plex Mono",monospace;font-size:12px;letter-spacing:.07em;text-transform:uppercase;color:var(--accent);font-weight:500}
h1{font-family:"Space Grotesk",sans-serif;font-weight:600;font-size:clamp(26px,4vw,34px);line-height:1.12;letter-spacing:-.015em;margin:8px 0 14px}
h2{font-family:"Space Grotesk",sans-serif;font-weight:600;font-size:20px;letter-spacing:-.01em;margin:0}
.lead{color:var(--muted);font-size:16px;max-width:62ch}
.meta-row{display:flex;flex-wrap:wrap;gap:8px;margin-top:18px}
.tag{font-family:"IBM Plex Mono",monospace;font-size:12px;color:var(--muted);background:var(--card);border:1px solid var(--line);border-radius:999px;padding:4px 11px}

/* tabs */
.tabs{display:flex;flex-wrap:wrap;gap:6px;margin:26px 0 22px;border-bottom:1px solid var(--line);padding-bottom:0}
.tab{font:inherit;font-size:13.5px;font-weight:500;color:var(--muted);background:transparent;border:none;border-bottom:2px solid transparent;padding:10px 14px;cursor:pointer;margin-bottom:-1px;display:flex;align-items:center;gap:7px}
.tab:hover{color:var(--ink)}
.tab.active{color:var(--accent);border-bottom-color:var(--accent);font-weight:600}
.tab .n{font-family:"IBM Plex Mono",monospace;font-size:11px;background:var(--accent-soft);color:var(--accent);border-radius:5px;padding:1px 6px}

.panel{display:none}
.panel.show{display:block;animation:fade .25s ease}
@keyframes fade{from{opacity:0;transform:translateY(4px)}to{opacity:1;transform:none}}

/* ELI5 hover reveal (folded into the Learn tab) */
.eli5-wrap{position:relative;display:inline-block;margin-bottom:16px;outline:none}
.eli5-chip{font-size:12.5px;font-weight:600;color:var(--amber);background:var(--amber-soft);border:1px solid transparent;border-radius:999px;padding:7px 14px;cursor:help;display:inline-flex;align-items:center;gap:7px;font-family:"IBM Plex Mono",monospace;letter-spacing:.02em}
.eli5-chip .ico{font-size:12px}
.eli5-chip .hov{opacity:.6;font-weight:500}
.eli5-wrap:hover .eli5-chip,.eli5-wrap:focus-visible .eli5-chip{border-color:var(--amber)}
.eli5-pop{display:none;position:absolute;top:calc(100% + 8px);left:0;z-index:20;width:min(480px,82vw);background:var(--amber-soft);border:1px solid var(--amber);border-radius:14px;padding:16px 18px;box-shadow:var(--shadow)}
.eli5-pop .stage-label{color:var(--amber);margin-bottom:10px}
.eli5-pop p{font-size:14.5px;margin-bottom:10px}
.eli5-pop p:last-child{margin-bottom:0}
.eli5-pop strong{font-weight:600}
.eli5-wrap:hover .eli5-pop,.eli5-wrap:focus-within .eli5-pop{display:block;animation:fade .18s ease}

.stage-card{border-radius:16px;padding:24px 26px;box-shadow:var(--shadow);border:1px solid var(--line)}
.stage-eli5{background:var(--amber-soft);border-color:transparent}
.stage-real{background:var(--card)}
.stage-label{font-family:"IBM Plex Mono",monospace;font-size:11px;letter-spacing:.06em;text-transform:uppercase;font-weight:500;margin-bottom:12px;display:inline-flex;align-items:center;gap:8px}
.stage-eli5 .stage-label{color:var(--amber)}
.stage-real .stage-label{color:var(--accent)}
.stage-card p{font-size:15.5px;margin-bottom:12px}
.stage-card p:last-child{margin-bottom:0}
.stage-card strong{font-weight:600}
.stage-real .stage-card-inner code{background:var(--mono-bg)}

/* real-deal rich content */
.stage-real h4{font-family:"Space Grotesk",sans-serif;font-size:15px;font-weight:600;margin:18px 0 8px;color:var(--ink)}
.stage-real ul{margin:6px 0 12px;padding-left:20px}
.stage-real li{font-size:15px;margin-bottom:6px}
.edge{margin-top:16px;border-left:3px solid var(--amber);background:var(--amber-soft);border-radius:0 10px 10px 0;padding:12px 16px;font-size:14.5px}
.edge b{font-family:"IBM Plex Mono",monospace;font-size:12px;letter-spacing:.04em;text-transform:uppercase;color:var(--amber);display:block;margin-bottom:4px}

/* worked example block (slash command / skill / config / API snippet) */
.example{margin-top:18px;border:1px solid var(--line);border-radius:12px;overflow:hidden;box-shadow:var(--shadow)}
.example b{display:block;font-family:"IBM Plex Mono",monospace;font-size:11px;letter-spacing:.05em;text-transform:uppercase;color:var(--accent-ink);font-weight:600;padding:9px 14px;background:var(--accent-soft);border-bottom:1px solid var(--line)}
.example pre{margin:0;padding:14px 16px;overflow-x:auto;background:var(--mono-bg);font-family:"IBM Plex Mono",monospace;font-size:12.5px;line-height:1.6;color:var(--mono-ink);white-space:pre;tab-size:2}
.example pre code{background:none;padding:0;border-radius:0;font-size:inherit;color:inherit;white-space:pre;word-break:normal}

/* "Recent in the docs" — additive, post-exam-guide updates (teal, distinct from exam-canonical content) */
.fresh{margin-top:18px;border-left:3px solid var(--teal);background:var(--teal-soft);border-radius:0 10px 10px 0;padding:13px 16px;font-size:14.5px}
.fresh > b.fl{font-family:"IBM Plex Mono",monospace;font-size:11px;letter-spacing:.04em;text-transform:uppercase;color:var(--teal);display:block;margin-bottom:7px}
.fresh ul{margin:4px 0 0;padding-left:18px}
.fresh li{margin-bottom:6px}
.fresh li:last-child{margin-bottom:0}
.fresh code{background:var(--mono-bg)}
.fresh a{color:var(--teal);text-decoration:underline;text-underline-offset:2px}

.callout{margin-top:18px;border-left:3px solid var(--accent);background:var(--accent-soft);border-radius:0 10px 10px 0;padding:12px 16px;font-size:14.5px}
.callout b{font-family:"IBM Plex Mono",monospace;font-size:12px;letter-spacing:.04em;text-transform:uppercase;color:var(--accent-ink);display:block;margin-bottom:4px}

/* questions */
.q-intro{font-size:14.5px;color:var(--muted);margin-bottom:18px}
.q{background:var(--card);border:1px solid var(--line);border-radius:14px;padding:20px 22px 18px;margin-bottom:14px;box-shadow:var(--shadow)}
.q-head{display:flex;gap:11px;align-items:flex-start;margin-bottom:13px}
.q-num{font-family:"Space Grotesk",sans-serif;font-weight:700;font-size:13px;color:var(--accent);background:var(--accent-soft);border-radius:8px;min-width:30px;height:30px;display:flex;align-items:center;justify-content:center;flex-shrink:0}
.q-domain{font-family:"IBM Plex Mono",monospace;font-size:10.5px;letter-spacing:.05em;text-transform:uppercase;color:var(--muted);margin-bottom:3px}
.q-text{font-size:15.5px;font-weight:500;line-height:1.5}
.opts{display:flex;flex-direction:column;gap:8px;margin-top:4px}
.opt{display:flex;gap:11px;align-items:flex-start;text-align:left;width:100%;background:transparent;border:1.5px solid var(--line);border-radius:11px;padding:11px 13px;cursor:pointer;font:inherit;color:var(--ink);transition:border-color .15s,background .15s}
.opt:hover{border-color:var(--accent)}
.opt:focus-visible{outline:2px solid var(--accent);outline-offset:2px}
.opt.sel{border-color:var(--accent);background:var(--accent-soft)}
.opt .key{font-family:"IBM Plex Mono",monospace;font-weight:500;font-size:12px;width:21px;height:21px;border-radius:6px;border:1.5px solid var(--line);display:flex;align-items:center;justify-content:center;flex-shrink:0;color:var(--muted)}
.opt.sel .key{border-color:var(--accent);background:var(--accent);color:#fff}
.opt .otext{font-size:14.5px;line-height:1.45}
.graded .opt{cursor:default}.graded .opt:hover{border-color:var(--line)}
.opt.correct{border-color:var(--correct);background:var(--correct-soft)}
.opt.correct .key{border-color:var(--correct);background:var(--correct);color:#fff}
.opt.wrong{border-color:var(--wrong);background:var(--wrong-soft)}
.opt.wrong .key{border-color:var(--wrong);background:var(--wrong);color:#fff}
.opt .mark{margin-left:auto;font-family:"IBM Plex Mono",monospace;font-size:11px;font-weight:500;align-self:center;white-space:nowrap}
.opt.correct .mark{color:var(--correct)}.opt.wrong .mark{color:var(--wrong)}
.explain{display:none;margin-top:13px;border-top:1px solid var(--line);padding-top:13px}
.explain.show{display:block}
.explain h4{font-family:"IBM Plex Mono",monospace;font-size:11px;letter-spacing:.06em;text-transform:uppercase;color:var(--muted);font-weight:500;margin-bottom:7px}
.explain p{font-size:14px;margin-bottom:10px}
.explain .traps{font-size:13.5px;color:var(--muted)}
.explain .traps>div{margin-bottom:7px}
.explain .traps b{color:var(--ink);font-weight:600;font-family:"IBM Plex Mono",monospace;font-size:12px}

.q-actions{display:flex;gap:12px;align-items:center;margin-top:18px;flex-wrap:wrap}
button.primary{font:inherit;font-weight:600;font-size:14.5px;background:var(--accent);color:#fff;border:none;border-radius:11px;padding:12px 24px;cursor:pointer;transition:opacity .15s}
button.primary:hover{opacity:.9}
button.primary:disabled{opacity:.45;cursor:not-allowed}
button.ghost{font:inherit;font-weight:500;font-size:13.5px;background:transparent;color:var(--muted);border:1.5px solid var(--line);border-radius:11px;padding:11px 18px;cursor:pointer}
button.ghost:hover{border-color:var(--accent);color:var(--accent)}
.hint{color:var(--muted);font-size:13px;font-family:"IBM Plex Mono",monospace}

.scorebox{display:none;background:var(--card);border:1px solid var(--line);border-radius:14px;padding:18px 20px;margin-bottom:20px;box-shadow:var(--shadow)}
.scorebox.show{display:block}
.scorebox .st{display:flex;align-items:baseline;justify-content:space-between;flex-wrap:wrap;gap:8px}
.scorebox .num{font-family:"Space Grotesk",sans-serif;font-weight:700;font-size:30px;letter-spacing:-.02em}
.verdict{font-family:"IBM Plex Mono",monospace;font-size:12px;font-weight:500;padding:5px 12px;border-radius:999px}
.verdict.pass{background:var(--correct-soft);color:var(--correct)}
.verdict.fail{background:var(--wrong-soft);color:var(--wrong)}
.scaled{color:var(--muted);font-size:13px;margin-top:5px}
.bar{height:7px;background:var(--line);border-radius:999px;margin-top:13px;overflow:hidden;position:relative}
.bar-fill{height:100%;width:0;background:var(--accent);border-radius:999px;transition:width .6s cubic-bezier(.4,0,.2,1)}
.bar-mark{position:absolute;top:-3px;bottom:-3px;left:72%;width:2px;background:var(--ink);opacity:.35}

/* home */
.home-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(220px,1fr));gap:14px;margin-top:26px}
.dcard{text-align:left;background:var(--card);border:1px solid var(--line);border-radius:14px;padding:18px;cursor:pointer;box-shadow:var(--shadow);transition:transform .15s,border-color .15s}
.dcard:hover{transform:translateY(-2px);border-color:var(--accent)}
.dcard .dn{font-family:"IBM Plex Mono",monospace;font-size:11px;color:var(--accent);letter-spacing:.05em}
.dcard h3{font-family:"Space Grotesk",sans-serif;font-size:16px;font-weight:600;margin:6px 0 8px;line-height:1.25}
.dcard .dw{font-size:12.5px;color:var(--muted)}
.dcard .dprog{margin-top:12px;height:5px;background:var(--line);border-radius:999px;overflow:hidden}
.dcard .dprog>div{height:100%;background:var(--accent);width:0;border-radius:999px;transition:width .4s}

/* exam scenarios */
.scen-list{display:flex;flex-direction:column;gap:14px;margin-top:26px}
.scen-card{background:var(--card);border:1px solid var(--line);border-radius:14px;padding:20px 22px;box-shadow:var(--shadow)}
.scen-card .scen-n{font-family:"IBM Plex Mono",monospace;font-size:11px;letter-spacing:.06em;text-transform:uppercase;color:var(--accent);font-weight:600}
.scen-card h3{font-family:"Space Grotesk",sans-serif;font-size:18px;font-weight:600;margin:5px 0 9px;line-height:1.25}
.scen-card p{font-size:14.5px;color:var(--muted);margin-bottom:14px}
.scen-doms{display:flex;flex-wrap:wrap;gap:7px}
.dchip{font:inherit;font-size:12px;font-weight:500;color:var(--accent-ink);background:var(--accent-soft);border:1px solid transparent;border-radius:999px;padding:6px 12px;cursor:pointer}
.dchip:hover{border-color:var(--accent)}

/* mobile */
.menu-btn{display:none;position:fixed;top:14px;left:14px;z-index:40;background:var(--card);border:1px solid var(--line);border-radius:10px;width:42px;height:42px;cursor:pointer;font-size:18px;color:var(--ink);box-shadow:var(--shadow)}
.scrim{display:none;position:fixed;inset:0;background:rgba(0,0,0,.4);z-index:30}
@media (max-width:860px){
  .menu-btn{display:flex;align-items:center;justify-content:center}
  .sidebar{position:fixed;left:0;top:0;z-index:35;transform:translateX(-100%);transition:transform .25s;box-shadow:0 0 40px rgba(0,0,0,.2)}
  .sidebar.open{transform:none}
  .scrim.open{display:block}
  .main{padding-top:68px}
}
@media (prefers-reduced-motion: reduce){*{transition:none!important;animation:none!important}}

/* ---------- auth gate ---------- */
.auth-overlay{position:fixed;inset:0;z-index:1000;background:var(--paper);display:flex;align-items:center;justify-content:center;padding:24px}
.auth-card{width:100%;max-width:380px;background:var(--card);border:1px solid var(--line);border-radius:16px;box-shadow:var(--shadow);padding:28px 26px;display:flex;flex-direction:column;gap:14px}
.auth-brand{display:flex;align-items:center;gap:10px;padding-bottom:8px}
.auth-brand .logo{font-family:"Space Grotesk",sans-serif;font-weight:700;font-size:15px;width:34px;height:34px;border-radius:9px;background:var(--accent);color:#fff;display:flex;align-items:center;justify-content:center;flex-shrink:0}
.auth-brand .bt{font-family:"Space Grotesk",sans-serif;font-weight:600}
.auth-brand .bs{font-family:"IBM Plex Mono",monospace;font-size:10.5px;color:var(--muted);letter-spacing:.04em}
.auth-tabs{display:flex;gap:6px;background:var(--accent-soft);border-radius:9px;padding:4px}
.auth-tab{flex:1;border:none;background:transparent;border-radius:7px;padding:8px;font:inherit;font-size:13px;font-weight:600;color:var(--muted);cursor:pointer}
.auth-tab.active{background:var(--card);color:var(--ink);box-shadow:var(--shadow)}
.auth-field{display:flex;flex-direction:column;gap:5px;font-size:12.5px;font-weight:600;color:var(--muted)}
.auth-field input{font:inherit;font-size:14px;font-weight:500;color:var(--ink);background:var(--paper);border:1px solid var(--line);border-radius:9px;padding:10px 12px}
.auth-field input:focus{outline:none;border-color:var(--accent);box-shadow:0 0 0 3px var(--accent-soft)}
.auth-err{color:var(--wrong);font-size:12.5px;font-weight:600;margin:0}
.auth-submit{font:inherit;font-size:14px;font-weight:600;color:#fff;background:var(--accent);border:none;border-radius:9px;padding:11px;cursor:pointer}
.auth-submit:disabled{opacity:.6;cursor:default}
.auth-hint{font-size:11.5px;color:var(--muted);text-align:center;margin:0}
.st-account{display:flex;align-items:center;justify-content:space-between;gap:8px;margin-top:12px;padding-top:12px;border-top:1px solid var(--line)}
.st-user{font-family:"IBM Plex Mono",monospace;font-size:12px;color:var(--muted)}