:root{
  --bg:#f7f8fb; --surface:#ffffff; --fg:#0b1220; --muted:#5b6478;
  --border:#e6e9ef; --primary:#2f5fff; --primary-2:#6c8cff; --primary-fg:#fff;
  --success:#16a34a; --danger:#dc2626; --soft:#eef2ff;
  --code-bg:#0f1424; --code-fg:#e6ecff;
  --shadow-sm:0 1px 2px rgba(15,20,40,.06);
  --shadow:0 8px 24px -12px rgba(47,95,255,.25);
  --shadow-glow:0 10px 30px -10px rgba(47,95,255,.45);
  --grad:linear-gradient(135deg,#2f5fff 0%,#6c8cff 100%);
  --grad-soft:linear-gradient(135deg,#eef2ff 0%,#fafbff 100%);
  --grad-hero:linear-gradient(180deg,#fafbff 0%,#ffffff 100%);
  --radius:14px;
}
*{box-sizing:border-box}
html,body{margin:0;padding:0}
body{
  font-family:"DM Sans",system-ui,-apple-system,Segoe UI,Roboto,sans-serif;
  background:var(--bg);color:var(--fg);line-height:1.55;
  -webkit-font-smoothing:antialiased;
}
h1,h2,h3,h4,.brand strong{font-family:"Space Grotesk",sans-serif;letter-spacing:-0.01em}
a{color:inherit;text-decoration:none}
code,pre{font-family:"JetBrains Mono",ui-monospace,Menlo,monospace}

.layout{display:flex;min-height:100vh}

/* Sidebar */
.sidebar{
  width:264px;flex-shrink:0;background:var(--surface);border-right:1px solid var(--border);
  padding:16px 12px;display:flex;flex-direction:column;gap:18px;position:sticky;top:0;height:100vh;overflow-y:auto;
}
.brand{display:flex;align-items:center;gap:10px;padding:6px 8px 14px;border-bottom:1px solid var(--border)}
.brand-logo{width:38px;height:38px;border-radius:11px;background:var(--grad);color:#fff;display:grid;place-items:center;font-weight:700;box-shadow:var(--shadow-glow)}
.brand-text{display:flex;flex-direction:column;line-height:1.1}
.brand-text strong{font-size:15px}
.brand-text small{color:var(--muted);font-size:11px;margin-top:2px}
.side-group{display:flex;flex-direction:column;gap:2px}
.side-label{font-size:11px;text-transform:uppercase;letter-spacing:.08em;color:var(--muted);padding:6px 10px 4px;font-weight:600}
.side-link{display:flex;align-items:center;gap:10px;padding:8px 10px;border-radius:10px;font-size:14px;color:var(--fg);transition:.15s}
.side-link:hover{background:var(--soft)}
.side-link.active{background:var(--soft);color:var(--primary);font-weight:600}
.num-chip{display:inline-grid;place-items:center;width:24px;height:24px;border-radius:7px;font-size:11px;font-weight:700;background:#eef0f5;color:#2a3142;flex-shrink:0}
.num-chip.on{background:var(--grad);color:#fff;box-shadow:var(--shadow-sm)}
.truncate{overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.side-card{margin-top:auto;padding:14px;border-radius:14px;background:var(--grad-soft);border:1px solid var(--border)}
.side-card-icon{width:30px;height:30px;border-radius:9px;display:grid;place-items:center;background:#fff;color:var(--primary);font-weight:700;box-shadow:var(--shadow-sm);margin-bottom:8px}
.side-card strong{font-size:13px;display:block}
.side-card p{margin:4px 0 0;font-size:12px;color:var(--muted)}

/* Main */
.main{flex:1;min-width:0;display:flex;flex-direction:column}
.topbar{position:sticky;top:0;z-index:20;display:flex;align-items:center;gap:12px;height:54px;padding:0 18px;background:rgba(255,255,255,.85);backdrop-filter:blur(10px);border-bottom:1px solid var(--border)}
.icon-btn{background:transparent;border:1px solid var(--border);width:34px;height:34px;border-radius:9px;display:grid;place-items:center;cursor:pointer;color:var(--fg)}
.icon-btn:hover{background:var(--soft)}
.spacer{flex:1}
.topbar-hint{color:var(--muted);font-size:12px}
.content{padding:32px 28px;max-width:1100px;margin:0 auto;width:100%}
.footer{padding:24px;text-align:center;color:var(--muted);font-size:12px;border-top:1px solid var(--border)}

/* Hero */
.hero{padding:36px 0 18px;text-align:center}
.pill{display:inline-block;padding:5px 12px;border-radius:999px;background:var(--soft);color:var(--primary);font-size:12px;font-weight:600;margin-bottom:18px}
.hero h1{font-size:clamp(32px,5vw,52px);font-weight:700;line-height:1.05;margin:0 0 14px}
.accent{background:var(--grad);-webkit-background-clip:text;background-clip:text;color:transparent}
.lead{font-size:17px;color:var(--muted);max-width:640px;margin:0 auto 24px}
.hero-actions{display:flex;gap:12px;justify-content:center;flex-wrap:wrap}
.btn-primary{display:inline-flex;align-items:center;gap:6px;padding:11px 20px;border-radius:11px;background:var(--grad);color:#fff;font-weight:600;border:0;cursor:pointer;font-size:14px;box-shadow:var(--shadow-glow);transition:.15s}
.btn-primary:hover{transform:translateY(-1px)}
.btn-ghost{display:inline-flex;align-items:center;gap:6px;padding:10px 18px;border-radius:11px;background:#fff;border:1px solid var(--border);font-weight:500;cursor:pointer;font-size:14px;color:var(--fg);transition:.15s}
.btn-ghost:hover{background:var(--soft);border-color:var(--primary)}

/* Stats */
.stats{display:grid;grid-template-columns:repeat(auto-fit,minmax(140px,1fr));gap:14px;margin:36px 0}
.stat{padding:18px;background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);text-align:center;box-shadow:var(--shadow-sm)}
.stat-num{font-family:"Space Grotesk";font-size:30px;font-weight:700;color:var(--primary)}
.stat-lbl{color:var(--muted);font-size:12px;margin-top:2px;text-transform:uppercase;letter-spacing:.06em}

/* Grid modules */
.section-title{font-size:24px;margin:30px 0 14px}
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:16px}
.card{display:block;padding:20px;background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);box-shadow:var(--shadow-sm);transition:.18s;cursor:pointer}
.card:hover{border-color:var(--primary);box-shadow:var(--shadow);transform:translateY(-2px)}
.card-head{display:flex;justify-content:space-between;align-items:center;margin-bottom:12px}
.num-badge{font-family:"Space Grotesk";font-weight:700;font-size:13px;padding:6px 10px;border-radius:9px;background:var(--grad);color:#fff;box-shadow:var(--shadow-sm)}
.num-badge.big{font-size:18px;padding:10px 14px;border-radius:14px}
.lvl{font-size:10px;padding:3px 9px;border-radius:999px;text-transform:uppercase;letter-spacing:.08em;font-weight:700}
.lvl-beg{background:rgba(22,163,74,.1);color:var(--success)}
.lvl-int{background:rgba(47,95,255,.1);color:var(--primary)}
.lvl-adv{background:rgba(220,38,38,.1);color:var(--danger)}
.card h3{margin:0 0 6px;font-size:17px}
.card p{margin:0;color:var(--muted);font-size:14px}
.card-foot{display:flex;justify-content:space-between;color:var(--muted);font-size:12px;margin-top:14px;padding-top:12px;border-top:1px solid var(--border)}

/* Module page */
.mod-hero{padding:30px 0 18px;border-bottom:1px solid var(--border);margin-bottom:24px;background:var(--grad-hero);margin:-32px -28px 24px;padding:30px 28px 22px}
.back-link{color:var(--muted);font-size:13px}
.back-link:hover{color:var(--primary)}
.mod-meta{display:flex;align-items:center;gap:10px;margin:14px 0 12px;flex-wrap:wrap}
.muted{color:var(--muted);font-size:12px}
.mod-hero h1{font-size:34px;margin:6px 0 6px}

/* Tabs */
.tabs{display:flex;gap:4px;padding:5px;background:#eef0f5;border-radius:12px;margin-bottom:24px}
.tab{flex:1;padding:9px 14px;border-radius:9px;border:0;background:transparent;cursor:pointer;font-weight:600;font-size:14px;color:var(--muted);transition:.15s;font-family:inherit}
.tab.active{background:#fff;color:var(--fg);box-shadow:var(--shadow-sm)}
.tab-panel{display:none}
.tab-panel.active{display:block;animation:fadeIn .25s ease}
@keyframes fadeIn{from{opacity:0;transform:translateY(4px)}to{opacity:1;transform:none}}

/* Panels */
.panel{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);padding:22px;margin-bottom:16px;box-shadow:var(--shadow-sm)}
.panel h2{margin:0 0 10px;font-size:19px}
.panel h3{margin:0 0 4px;font-size:17px}
.panel p{margin:0;color:#2a3142}

/* Code */
.code-block{margin-top:14px;border-radius:12px;overflow:hidden;background:var(--code-bg);box-shadow:var(--shadow-sm)}
.code-bar{display:flex;align-items:center;gap:7px;padding:9px 14px;background:rgba(255,255,255,.04);border-bottom:1px solid rgba(255,255,255,.08)}
.dot{width:11px;height:11px;border-radius:50%}
.dot.r{background:#ff5f57}.dot.y{background:#febc2e}.dot.g{background:#28c840}
.code-lang{margin-left:10px;font-size:10px;letter-spacing:.12em;color:rgba(255,255,255,.4);text-transform:uppercase}
.copy-btn{margin-left:auto;background:rgba(255,255,255,.06);border:0;color:rgba(255,255,255,.7);padding:5px 10px;border-radius:6px;font-size:11px;cursor:pointer;font-family:inherit}
.copy-btn:hover{background:rgba(255,255,255,.12);color:#fff}
.copy-btn.ok{background:rgba(34,197,94,.2);color:#86efac}
pre{margin:0;padding:16px;overflow-x:auto;color:var(--code-fg);font-size:13px;line-height:1.65}

/* Exos */
.exo-head{display:flex;gap:12px;align-items:flex-start}
.exo-actions{display:flex;gap:8px;margin-top:14px;flex-wrap:wrap}
.hint{margin-top:14px;padding:12px 14px;border:1px solid rgba(47,95,255,.3);background:rgba(47,95,255,.05);border-radius:10px;font-size:14px;color:#1e3a8a}
.hidden{display:none}

/* QCM */
.qcm{display:flex;flex-direction:column;gap:14px}
.q{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);padding:18px;box-shadow:var(--shadow-sm);margin:0}
.q legend{font-weight:600;padding:0 6px;display:flex;align-items:center;gap:10px;font-size:15px}
.opt{display:flex;align-items:center;gap:10px;padding:10px 12px;border-radius:9px;cursor:pointer;border:1px solid transparent;transition:.12s;font-size:14px}
.opt:hover{background:var(--soft)}
.opt input{accent-color:var(--primary)}
.opt.correct{background:rgba(22,163,74,.1);border-color:var(--success);color:#14532d;font-weight:500}
.opt.wrong{background:rgba(220,38,38,.08);border-color:var(--danger);color:#7f1d1d}
.qcm-actions{display:flex;gap:10px;flex-wrap:wrap;margin-top:6px}
.qcm-result{padding:18px;border-radius:var(--radius);background:var(--grad-soft);border:1px solid var(--border);font-size:15px;text-align:center}
.qcm-result strong{font-size:24px;display:block;color:var(--primary);font-family:"Space Grotesk"}

/* Nav module */
.mod-nav{display:flex;justify-content:space-between;gap:14px;margin-top:36px;padding-top:24px;border-top:1px solid var(--border)}
.nav-card{flex:0 1 280px;padding:14px 18px;background:var(--surface);border:1px solid var(--border);border-radius:12px;display:flex;flex-direction:column;box-shadow:var(--shadow-sm);transition:.15s}
.nav-card:hover{border-color:var(--primary)}
.nav-card.next{background:var(--grad);color:#fff;border:0;box-shadow:var(--shadow-glow);text-align:right}
.nav-card small{font-size:10px;text-transform:uppercase;letter-spacing:.08em;opacity:.7}
.nav-card strong{font-size:14px;margin-top:2px}

.empty{text-align:center;padding:80px 20px}
.empty h1{font-size:60px;margin:0}

/* Responsive */
@media (max-width:880px){
  .sidebar{position:fixed;left:-280px;height:100vh;z-index:50;transition:.25s;box-shadow:var(--shadow)}
  .sidebar.open{left:0}
  .content{padding:22px 18px}
  .mod-hero{margin:-22px -18px 20px;padding:24px 18px}
}
@media (min-width:881px){
  #sideToggle{display:none}
}