:root{
  --bg:#f5f4f0; --surface:#fff; --surface-alt:#f1efe8; --ink:#1b2430; --ink-soft:#5a6472; --ink-faint:#8b93a0;
  --border:#ddd8cc; --border-soft:#e8e4d9; --accent:#8f6317; --accent-ink:#5c3f0c; --accent-soft:#f1e5c9;
  --teal:#2f6b67; --teal-soft:#e2eeec; --good:#1f7a4d; --good-soft:#e2f1e8; --warn:#946012; --warn-soft:#faf0da; --bad:#a8341f; --bad-soft:#f7e2dd;
  --sidebar-bg:#0d1420; --sidebar-ink:#c7cedb; --sidebar-ink-dim:#7c8798; --sidebar-active:#182338; --sidebar-border:#1c2536;
  --btn-primary-bg:#5c3f0c; --btn-primary-ink:#fdf6e8; --th-ink:#173a63;
  --formula-ink:#0e7490; --formula-bg:#e5f7fa; --formula-border:#a9e4ee;
  --shadow:0 1px 2px rgba(27,36,48,.05),0 6px 20px -10px rgba(27,36,48,.15);
}
@media (prefers-color-scheme: dark){:root:not([data-theme="light"]){
  --bg:#0e141b; --surface:#161d26; --surface-alt:#1c2430; --ink:#e9e7df; --ink-soft:#aab1bd; --ink-faint:#7c8492;
  --border:#2b333f; --border-soft:#232b36; --accent:#dcac52; --accent-ink:#f2d799; --accent-soft:#332a17;
  --teal:#6fb2ab; --teal-soft:#152623; --good:#6cc296; --good-soft:#132921; --warn:#e0b45c; --warn-soft:#2e2610; --bad:#e0906c; --bad-soft:#2e1c15;
  --btn-primary-bg:#dcac52; --btn-primary-ink:#241a06; --th-ink:#8fc1ee; --formula-ink:#7fe3f2; --formula-bg:#0f2a30; --formula-border:#1c4750;
}}
:root[data-theme="dark"]{
  --bg:#0e141b; --surface:#161d26; --surface-alt:#1c2430; --ink:#e9e7df; --ink-soft:#aab1bd; --ink-faint:#7c8492;
  --border:#2b333f; --border-soft:#232b36; --accent:#dcac52; --accent-ink:#f2d799; --accent-soft:#332a17;
  --teal:#6fb2ab; --teal-soft:#152623; --good:#6cc296; --good-soft:#132921; --warn:#e0b45c; --warn-soft:#2e2610; --bad:#e0906c; --bad-soft:#2e1c15;
  --btn-primary-bg:#dcac52; --btn-primary-ink:#241a06; --th-ink:#8fc1ee; --formula-ink:#7fe3f2; --formula-bg:#0f2a30; --formula-border:#1c4750;
}
*{box-sizing:border-box}
html,body{margin:0;background:var(--bg);color:var(--ink);font:14px/1.55 "IBM Plex Sans",system-ui,sans-serif}
.shell{display:flex;min-height:100vh}
/* ---------- sidebar ---------- */
.sidebar{width:264px;flex:none;background:var(--sidebar-bg);color:var(--sidebar-ink);position:sticky;top:0;height:100vh;overflow-y:auto;display:flex;flex-direction:column}
.brand{display:flex;gap:10px;align-items:center;padding:18px 18px 14px;border-bottom:1px solid var(--sidebar-border)}
.brand-mark{background:#dcac52;color:#241a06;font:700 .78rem "IBM Plex Mono",ui-monospace,monospace;padding:6px 7px;border-radius:6px}
.brand .name{font-weight:700;color:#f6efe0}.brand .sub{font:.66rem "IBM Plex Mono",ui-monospace,monospace;color:var(--sidebar-ink-dim);letter-spacing:.04em}
.nav{padding:8px 10px 20px;flex:1}
.grp{all:unset;box-sizing:border-box;width:100%;display:flex;align-items:center;justify-content:space-between;cursor:pointer;
  font:600 .68rem "IBM Plex Mono",ui-monospace,monospace;letter-spacing:.09em;text-transform:uppercase;color:var(--sidebar-ink-dim);padding:12px 10px 6px;border-left:2px solid transparent}
.grp:hover{color:var(--sidebar-ink)}
.grp.open{color:#f2d799;border-left-color:#dcac52}
.grp .chev{transition:transform .15s;font-size:.7rem}.grp.open .chev{transform:rotate(90deg)}
.phase{font:500 .64rem "IBM Plex Mono",ui-monospace,monospace;letter-spacing:.08em;text-transform:uppercase;color:var(--sidebar-ink-dim);
  padding:10px 10px 4px 20px;display:flex;align-items:center;gap:8px}
.phase::after{content:"";flex:1;height:1px;background:var(--sidebar-border)}
.item{all:unset;box-sizing:border-box;width:100%;display:flex;align-items:center;gap:9px;cursor:pointer;padding:6px 10px 6px 20px;border-radius:7px;
  font-size:.83rem;color:var(--sidebar-ink);margin-bottom:1px}
.item:hover{background:var(--sidebar-active)}
.item.active{background:var(--sidebar-active);color:#f6efe0;font-weight:600}
.item svg{flex:none;width:15px;height:15px;opacity:.8}
.item.active svg{color:#dcac52;opacity:1}
.item .lbl{flex:1}
.dots{display:flex;gap:3px}.dot{width:6px;height:6px;border-radius:50%}
.dot.s{background:#6cc296}.dot.t{background:#dcac52}.dot.o{border:1px solid var(--sidebar-ink-dim)}
.ghost{font-size:.78rem;color:var(--sidebar-ink-dim);padding:4px 10px 4px 20px;font-style:italic}
.foot{padding:12px 16px 16px;border-top:1px solid var(--sidebar-border);font-size:.66rem;color:var(--sidebar-ink-dim)}
.foot .k{display:flex;align-items:center;gap:6px;margin-top:4px}
/* ---------- main ---------- */
.main{flex:1;min-width:0;display:flex;flex-direction:column}
.topbar{display:flex;align-items:center;gap:12px;padding:12px 26px;border-bottom:1px solid var(--border);background:var(--surface)}
.crumb{font:500 .78rem "IBM Plex Mono",ui-monospace,monospace;color:var(--ink-soft)}.crumb b{color:var(--ink)}
.sp{flex:1}
.pill{font:700 .7rem "IBM Plex Mono",ui-monospace,monospace;padding:4px 10px;border-radius:999px;background:var(--sidebar-bg);color:#f2efe6}
.pill.g{background:var(--good-soft);color:var(--good)}
.layers-btn{all:unset;cursor:pointer;font:600 .75rem "IBM Plex Mono",ui-monospace,monospace;padding:5px 10px;border-radius:6px;border:1px solid var(--border);color:var(--ink-soft)}
.layers-btn.on{background:var(--accent-soft);color:var(--accent-ink);border-color:var(--accent)}
.content{padding:22px 30px 50px;max-width:1160px}
.mod-head{display:flex;align-items:flex-start;gap:16px;flex-wrap:wrap}
.mod-head h1{margin:0;font-size:1.5rem;letter-spacing:-.01em}
.mod-head .full{color:var(--ink-soft);font-size:.86rem;margin-top:2px}
.toggle{display:inline-flex;background:var(--surface-alt);border:1px solid var(--border);border-radius:9px;padding:3px;margin-left:auto}
.toggle button{all:unset;cursor:pointer;font:600 .8rem "IBM Plex Sans";padding:6px 16px;border-radius:7px;color:var(--ink-soft)}
.toggle button.on{background:var(--surface);color:var(--ink);box-shadow:var(--shadow)}
.toggle button[disabled]{opacity:.4;cursor:not-allowed}
.tabs{display:flex;flex-wrap:wrap;gap:2px;border-bottom:1px solid var(--border);margin:18px 0 0}
.tab{all:unset;cursor:pointer;white-space:nowrap;padding:9px 14px;font-size:.84rem;color:var(--ink-soft);border-bottom:2px solid transparent;margin-bottom:-1px}
.tab.on{color:var(--ink);font-weight:600;border-bottom-color:var(--accent)}
.page{background:var(--surface);border:1px solid var(--border);border-top:0;border-radius:0 0 10px 10px;padding:20px 24px 18px;box-shadow:var(--shadow)}
.page h1{font-size:1.2rem;margin:0 0 6px}
h2{font-size:1rem;margin:20px 0 6px;color:var(--th-ink)} h3{font-size:.95rem;margin:16px 0 6px}
.lead{color:var(--ink-soft);margin:0 0 12px}
.tw{overflow-x:auto;margin:10px 0 16px;border:1px solid var(--border);border-radius:8px}
table{border-collapse:collapse;width:100%;font-size:.82rem}
th{text-align:left;padding:8px 10px;background:var(--surface-alt);color:var(--th-ink);font:600 .72rem "IBM Plex Mono",ui-monospace,monospace;text-transform:uppercase;letter-spacing:.04em;white-space:nowrap;border-bottom:1px solid var(--border)}
td{padding:8px 10px;border-top:1px solid var(--border-soft);vertical-align:top}
td:first-child{font-weight:600}
.flow{display:flex;flex-wrap:wrap;gap:6px;margin:10px 0 16px}
.step{flex:1 1 120px;background:var(--surface-alt);border:1px solid var(--border);border-top:3px solid var(--teal);border-radius:8px;padding:9px 10px;font-size:.78rem;color:var(--ink-soft)}
.step b{display:block;color:var(--ink);font-size:.82rem;margin-bottom:2px}
.step .n{display:inline-block;width:18px;height:18px;border-radius:50%;background:var(--teal);color:#fff;font:600 .66rem/18px "IBM Plex Mono",ui-monospace,monospace;text-align:center;margin-right:5px}
.arrow{align-self:center;color:var(--ink-faint)}
.call{background:var(--warn-soft);border-left:3px solid var(--warn);padding:9px 13px;border-radius:6px;margin:12px 0;font-size:.86rem}
.info{background:var(--formula-bg);border-left:3px solid var(--formula-border);padding:9px 13px;border-radius:6px;margin:12px 0;font-size:.86rem}
.pager{display:flex;align-items:center;justify-content:space-between;margin-top:22px;padding-top:14px;border-top:1px solid var(--border-soft)}
.btn{all:unset;cursor:pointer;background:var(--btn-primary-bg);color:var(--btn-primary-ink);font-weight:600;font-size:.84rem;padding:8px 16px;border-radius:7px}
.btn.sec{background:var(--surface-alt);color:var(--ink);border:1px solid var(--border)}
.btn[disabled]{opacity:.35;cursor:default}
.pg{font:500 .74rem "IBM Plex Mono",ui-monospace,monospace;color:var(--ink-faint)}
.badge{display:inline-block;font:600 .68rem "IBM Plex Mono",ui-monospace,monospace;padding:2px 8px;border-radius:999px}
.b-good{background:var(--good-soft);color:var(--good)}.b-warn{background:var(--warn-soft);color:var(--warn)}.b-bad{background:var(--bad-soft);color:var(--bad)}
.b-n{background:var(--surface-alt);color:var(--ink-soft);border:1px solid var(--border)}
.legrow td{background:var(--surface-alt);font-weight:400!important}
.legrow td:first-child{padding-left:30px;color:var(--ink-soft)}
.expander{all:unset;cursor:pointer;color:var(--accent);font-weight:700;width:16px;display:inline-block}
.empty{border:1px dashed var(--border);border-radius:10px;padding:26px;text-align:center;color:var(--ink-soft);background:var(--surface)}
/* layer annotations */
.L{display:none;font:700 .6rem "IBM Plex Mono",ui-monospace,monospace;background:#dcac52;color:#241a06;border-radius:4px;padding:1px 5px;margin-left:6px;white-space:nowrap;vertical-align:middle}
body.show-layers .L{display:inline-block}
.legend{display:none;margin:0 0 16px;background:var(--surface);border:1px solid var(--accent);border-radius:10px;padding:12px 16px;box-shadow:var(--shadow)}
body.show-layers .legend{display:block}
.legend .row{display:grid;grid-template-columns:44px 210px 1fr;gap:10px;padding:5px 0;border-top:1px solid var(--border-soft);font-size:.82rem;align-items:center}
.legend .row:first-of-type{border-top:0}
.legend .tag{font:700 .68rem "IBM Plex Mono",ui-monospace,monospace;background:#dcac52;color:#241a06;border-radius:4px;padding:2px 6px;text-align:center}
.menu-btn{display:none}
@media (max-width:880px){
  .sidebar{position:fixed;z-index:20;transform:translateX(-100%);transition:transform .2s}
  .sidebar.open{transform:none;box-shadow:0 0 0 100vmax rgba(0,0,0,.45)}
  .menu-btn{display:inline-flex}
  .content{padding:16px}
  .topbar{padding:10px 16px;flex-wrap:wrap}
  .legend .row{grid-template-columns:40px 1fr}.legend .row span:last-child{grid-column:1/-1}
  .toggle{margin-left:0}
}

/* ---- master: engine frame ---- */
.eng-bar{display:flex;flex-wrap:wrap;align-items:center;gap:10px;margin:0 0 10px;font-size:.82rem;color:var(--ink-soft)}
.eng-bar .st{font:600 .72rem "IBM Plex Mono",ui-monospace,monospace;padding:3px 8px;border-radius:6px;border:1px solid var(--border)}
.eng-bar .st.live{color:#1d6b3a;border-color:#8cc59e;background:#e7f4ea}.eng-bar .st.local{color:#8a5a00;border-color:#e2c47c;background:#fbf1d8}
iframe.gfm{width:100%;height:calc(100vh - 150px);min-height:620px;border:1px solid var(--border);border-radius:10px;background:#f3f5f7;display:block}
.content.wide{max-width:none}
iframe.eng{width:100%;min-height:640px;opacity:0;transition:opacity .25s;overflow-anchor:none;border:1px solid var(--border);border-radius:10px;background:#faf9f5;display:block}
.prop-h{margin:26px 0 8px;font-size:1.02rem}
.grp .tagx{font:600 .62rem "IBM Plex Mono",monospace;margin-left:6px;padding:1px 5px;border-radius:4px;background:var(--accent-soft);color:var(--accent-ink)}
.xref{color:var(--accent);font-weight:600;text-decoration:none;border-bottom:1px dotted var(--accent)}
.xsub{font:600 .66rem "IBM Plex Mono",monospace;color:var(--ink-faint);text-transform:uppercase;letter-spacing:.06em;padding:8px 12px 2px}

/* ---- learner platform additions ---- */
.auth-wrap{min-height:100vh;display:flex;align-items:center;justify-content:center;background:var(--sidebar-bg);padding:16px;box-sizing:border-box}
.auth-card{background:var(--surface);color:var(--ink);border-radius:14px;padding:28px 30px;width:100%;max-width:420px;box-shadow:0 20px 60px -20px rgba(0,0,0,.5)}
.auth-card h1{font-size:1.25rem;margin:18px 0 12px}
.auth-brand{padding:0!important;border:0!important}.auth-brand .name{color:var(--ink)!important}.auth-brand .sub{color:var(--ink-faint)!important}
.auth-card form{display:grid;gap:12px}.auth-card label{display:grid;gap:4px;font-size:.8rem;color:var(--ink-soft)}
.auth-card input{font:inherit;font-size:.95rem;padding:9px 10px;border:1px solid var(--border);border-radius:8px;background:var(--surface);color:var(--ink)}
.auth-card .btn{justify-self:start;margin-top:4px}.auth-links{margin:12px 0 0;font-size:.85rem}.auth-links a{color:var(--accent)}
.auth-note{font-size:.78rem;color:var(--ink-faint);margin:10px 0 0}.auth-foot{font-size:.7rem;color:var(--ink-faint);margin:22px 0 0;border-top:1px solid var(--border-soft);padding-top:10px}
.auth-msg{font-size:.84rem;padding:9px 11px;border-radius:8px;margin:0 0 12px;background:var(--surface-alt)}.auth-msg.bad{background:var(--bad-soft);color:var(--bad)}.auth-msg.ok{background:var(--good-soft);color:var(--good)}
.who{display:flex;align-items:center;justify-content:space-between;gap:8px;padding:8px 14px;color:var(--sidebar-ink);font-size:.8rem;border-bottom:1px solid var(--sidebar-border)}
.who .badge{background:#243149;color:#dcac52;text-transform:uppercase}
.side-links{padding:6px 6px 2px;border-bottom:1px solid var(--sidebar-border)}
.ghost.locked{opacity:.7}.done-n{font:600 .62rem "IBM Plex Mono",monospace;color:#6cc296}
.tab.seen::after{content:" ✓";color:var(--good)}
.loading{padding:30px;color:var(--ink-faint)}
.btn.small{padding:5px 10px;font-size:.76rem}
.prog-row{display:grid;grid-template-columns:240px 1fr 60px;gap:12px;align-items:center;margin:8px 0;font-size:.86rem}
.prog-row .bar{height:10px;background:var(--surface-alt);border-radius:6px;overflow:hidden}.prog-row .bar i{display:block;height:100%;background:var(--accent)}
@media(max-width:640px){.prog-row{grid-template-columns:1fr 50px}.prog-row .bar{grid-column:1/-1;grid-row:2}}
.row-btns{display:flex;gap:8px;margin:8px 0 12px;flex-wrap:wrap}.grp-row td{background:var(--surface-alt)}
#adm select{font:inherit;font-size:.8rem;padding:3px 6px;border:1px solid var(--border);border-radius:6px;background:var(--surface);color:var(--ink)}
.toast{position:fixed;bottom:20px;left:50%;transform:translateX(-50%);background:var(--ink);color:var(--surface);padding:10px 16px;border-radius:8px;font-size:.85rem;z-index:99}