/* ================================================================
   Datanerves — Enterprise Design System
   Visual identity: professional technical training platform
   ================================================================ */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=JetBrains+Mono:wght@400;500&display=swap');

/* ── Tokens ─────────────────────────────────────────────────── */
:root {
  /* Core palette */
  --blue-900: #001141;
  --blue-800: #002678;
  --blue-700: #0043ce;
  --blue-600: #0f62fe;   /* primary interactive */
  --blue-500: #4589ff;
  --blue-400: #78a9ff;
  --blue-200: #a6c8ff;
  --blue-100: #d0e2ff;
  --blue-050: #edf5ff;

  --teal-600: #007d79;
  --teal-100: #d9fbfb;
  --teal-050: #f4f4f4;

  /* Application shell */
  --shell-bg:       #eef0f3;   /* page background */
  --nav-bg:         #1a2332;   /* top nav + left sidebar */
  --nav-border:     #243244;   /* border inside dark nav */
  --panel-bg:       #ffffff;   /* content panels */
  --panel-bg-2:     #f7f8fa;   /* panel secondary bg */

  /* Borders */
  --border:         #dde1e7;
  --border-strong:  #c6cbd5;
  --border-focus:   var(--blue-600);

  /* Text */
  --text-primary:   #161616;
  --text-secondary: #525252;
  --text-helper:    #8d8d8d;
  --text-disabled:  #c6c6c6;
  --text-inverse:   #f4f4f4;
  --text-link:      var(--blue-600);

  /* Semantic */
  --success:        #198038;
  --success-bg:     #defbe6;
  --success-border: #a7f0ba;
  --warning:        #b28600;
  --warning-bg:     #fdf6dd;
  --warning-border: #f1c21b;
  --error:          #da1e28;
  --error-bg:       #fff1f1;
  --error-border:   #ffd7d9;
  --info:           var(--blue-600);
  --info-bg:        var(--blue-050);
  --info-border:    var(--blue-100);

  /* Type tags */
  --course-color:   #0043ce;  --course-bg: #dde8ff;
  --lab-color:      #005d5d;  --lab-bg:    #d9fbfb;
  --cert-color:     #7e3a00;  --cert-bg:   #ffe8c9;
  --path-color:     #491d8b;  --path-bg:   #f6f2ff;
  --free-color:     #198038;  --free-bg:   #defbe6;
  --pro-color:      #491d8b;  --pro-bg:    #f6f2ff;

  /* Spacing — 4px unit */
  --s1:  4px;  --s2:  8px;  --s3:  12px; --s4:  16px;
  --s5:  20px; --s6:  24px; --s7:  28px; --s8:  32px;
  --s10: 40px; --s12: 48px; --s14: 56px; --s16: 64px;

  /* Layout */
  --nav-h:        52px;
  --sidebar-w:    240px;
  --content-max:  800px;
  --page-max:     1280px;
  --filter-w:     220px;

  /* Radii */
  --r1: 2px;
  --r2: 4px;
  --r3: 6px;
  --r4: 8px;

  /* Elevation — minimal, structural only */
  --e1: 0 1px 2px rgba(0,0,0,0.05);
  --e2: 0 2px 4px rgba(0,0,0,0.07);
}

/* ── Reset ──────────────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { text-size-adjust: 100%; }
body {
  font-family: 'Inter', -apple-system, 'Segoe UI', sans-serif;
  font-size: 14px;
  line-height: 1.5;
  color: var(--text-primary);
  background: var(--shell-bg);
  -webkit-font-smoothing: antialiased;
}
a { color: var(--text-link); text-decoration: none; }
a:hover { text-decoration: underline; }
button, input, select, textarea { font-family: inherit; font-size: inherit; }
img { max-width: 100%; display: block; }

/* ── Typography ─────────────────────────────────────────────── */
.t-display { font-size: 2.25rem; font-weight: 300; line-height: 1.15; letter-spacing: -0.025em; color: var(--text-primary); }
.t-h1 { font-size: 1.75rem;  font-weight: 600; line-height: 1.2;  letter-spacing: -0.02em; }
.t-h2 { font-size: 1.375rem; font-weight: 600; line-height: 1.25; letter-spacing: -0.015em; }
.t-h3 { font-size: 1.125rem; font-weight: 600; line-height: 1.3;  }
.t-h4 { font-size: 0.9375rem; font-weight: 600; line-height: 1.4; }
.t-h5 { font-size: 0.875rem;  font-weight: 600; line-height: 1.4; }
.t-body-lg { font-size: 1rem;     line-height: 1.75; color: var(--text-secondary); }
.t-body    { font-size: 0.9375rem; line-height: 1.7;  color: var(--text-secondary); }
.t-body-sm { font-size: 0.875rem;  line-height: 1.6;  color: var(--text-secondary); }
.t-sm      { font-size: 0.8125rem; line-height: 1.55; color: var(--text-secondary); }
.t-xs      { font-size: 0.75rem;   line-height: 1.5;  color: var(--text-helper); }
.t-label   { font-size: 0.6875rem; font-weight: 600; letter-spacing: 0.06em; text-transform: uppercase; color: var(--text-helper); }
.t-mono    { font-family: 'JetBrains Mono', monospace; }
.t-link    { color: var(--text-link); }
.t-muted   { color: var(--text-helper); }
.t-inv     { color: var(--text-inverse); }

/* ── Navigation — top bar ───────────────────────────────────── */
.topnav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 600;
  height: var(--nav-h);
  background: var(--nav-bg);
  border-bottom: 1px solid var(--nav-border);
  display: flex;
  align-items: center;
}
.topnav-inner {
  width: 100%;
  max-width: var(--page-max);
  margin: 0 auto;
  padding: 0 var(--s6);
  display: flex;
  align-items: center;
  height: 100%;
  gap: 0;
}

/* Brand */
.nav-brand {
  display: flex;
  align-items: center;
  gap: var(--s2);
  text-decoration: none;
  margin-right: var(--s6);
  flex-shrink: 0;
  padding-right: var(--s6);
  border-right: 1px solid var(--nav-border);
}
.nav-brand:hover { text-decoration: none; }
.brand-mark {
  width: 28px; height: 28px;
  background: var(--blue-600);
  border-radius: var(--r2);
  display: flex; align-items: center; justify-content: center;
  flex-shrink: 0;
}
.brand-wordmark {
  font-size: 0.9375rem;
  font-weight: 600;
  color: #e4e8f0;
  letter-spacing: -0.01em;
  line-height: 1;
}
.brand-wordmark em { font-style: normal; color: var(--blue-400); }

/* Nav items */
.nav-items {
  display: flex;
  align-items: center;
  height: 100%;
  flex: 1;
  overflow-x: auto;
  scrollbar-width: none;
  gap: 0;
}
.nav-items::-webkit-scrollbar { display: none; }
.nav-item {
  display: flex;
  align-items: center;
  gap: var(--s1);
  height: 100%;
  padding: 0 var(--s3);
  font-size: 0.875rem;
  font-weight: 500;
  color: #8fa3bc;
  text-decoration: none;
  border-bottom: 2px solid transparent;
  margin-bottom: -1px;
  white-space: nowrap;
  transition: color 0.12s;
  cursor: pointer;
  background: transparent;
  border-top: none; border-left: none; border-right: none;
  font-family: inherit;
}
.nav-item:hover { color: #c8d6e8; text-decoration: none; }
.nav-item.active { color: #ffffff; font-weight: 600; border-bottom-color: var(--blue-500); }
.nav-badge {
  font-size: 0.5625rem;
  font-weight: 700;
  background: #243650;
  color: #6b8aaa;
  padding: 1px 5px;
  border-radius: var(--r1);
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin-left: 2px;
}

/* Nav right */
.nav-right {
  display: flex;
  align-items: center;
  gap: var(--s2);
  margin-left: var(--s5);
  padding-left: var(--s5);
  border-left: 1px solid var(--nav-border);
  flex-shrink: 0;
}
.session-chip {
  display: flex;
  align-items: center;
  gap: 5px;
  padding: 4px 10px;
  background: rgba(25,128,56,0.15);
  border: 1px solid rgba(25,128,56,0.3);
  border-radius: var(--r2);
  font-size: 0.75rem;
  font-weight: 600;
  color: #42be65;
  text-decoration: none;
}
.session-chip:hover { background: rgba(25,128,56,0.22); text-decoration: none; color: #42be65; }
.live-dot {
  width: 6px; height: 6px;
  border-radius: 50%;
  background: #42be65;
}

/* User button */
.user-btn {
  display: flex;
  align-items: center;
  gap: var(--s2);
  padding: 5px 10px;
  background: transparent;
  border: 1px solid var(--nav-border);
  border-radius: var(--r2);
  color: #c8d6e8;
  font-size: 0.8125rem;
  font-weight: 500;
  cursor: pointer;
  transition: border-color 0.12s;
  position: relative;
}
.user-btn:hover { border-color: #3a5070; }
.user-avatar {
  width: 22px; height: 22px;
  border-radius: 50%;
  background: var(--blue-700);
  display: flex; align-items: center; justify-content: center;
  font-size: 10px; font-weight: 700; color: #fff;
  flex-shrink: 0;
}

/* Dropdown */
.user-dropdown {
  position: absolute;
  top: calc(100% + 6px);
  right: 0;
  background: var(--panel-bg);
  border: 1px solid var(--border);
  border-radius: var(--r3);
  min-width: 196px;
  z-index: 700;
  box-shadow: var(--e2);
  display: none;
}
.user-dropdown.open { display: block; }
.ud-head { padding: 10px 14px; border-bottom: 1px solid var(--border); background: var(--panel-bg-2); border-radius: var(--r3) var(--r3) 0 0; }
.ud-name { font-size: 0.875rem; font-weight: 600; color: var(--text-primary); }
.ud-sub  { font-size: 0.75rem; color: var(--text-helper); }
.ud-item { display: flex; align-items: center; gap: var(--s2); padding: 9px 14px; font-size: 0.875rem; color: var(--text-secondary); text-decoration: none; border-bottom: 1px solid var(--border); transition: background 0.1s; }
.ud-item:last-child { border-bottom: none; border-radius: 0 0 var(--r3) var(--r3); }
.ud-item:hover { background: var(--panel-bg-2); color: var(--text-primary); text-decoration: none; }
.ud-item.danger { color: var(--error); }
.ud-item.danger:hover { background: var(--error-bg); }

/* ── Buttons ─────────────────────────────────────────────────── */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--s2);
  font-family: inherit;
  font-weight: 600;
  border-radius: var(--r2);
  border: 1px solid transparent;
  cursor: pointer;
  text-decoration: none;
  white-space: nowrap;
  line-height: 1;
  transition: background 0.1s, border-color 0.1s, color 0.1s;
  -webkit-font-smoothing: antialiased;
}
.btn:hover { text-decoration: none; }
.btn:focus-visible { outline: 2px solid var(--blue-600); outline-offset: 2px; }
.btn:disabled, .btn[disabled] { opacity: 0.4; cursor: not-allowed; pointer-events: none; }

.btn-sm { padding: 6px 14px; font-size: 0.8125rem; }
.btn-md { padding: 9px 18px; font-size: 0.875rem; }
.btn-lg { padding: 11px 22px; font-size: 0.9375rem; }

.btn-primary   { background: var(--blue-600); color: #fff; border-color: var(--blue-600); }
.btn-primary:hover { background: var(--blue-700); border-color: var(--blue-700); color: #fff; }

.btn-secondary { background: var(--panel-bg); color: var(--text-primary); border-color: var(--border-strong); }
.btn-secondary:hover { background: var(--panel-bg-2); border-color: var(--text-helper); color: var(--text-primary); }

.btn-ghost { background: transparent; color: var(--blue-600); border-color: transparent; }
.btn-ghost:hover { background: var(--info-bg); color: var(--blue-700); }

.btn-danger { background: var(--error); color: #fff; border-color: var(--error); }
.btn-danger:hover { background: #b81922; border-color: #b81922; color: #fff; }

.btn-block { width: 100%; }

/* ── Tags / badges ──────────────────────────────────────────── */
.tag {
  display: inline-flex;
  align-items: center;
  gap: var(--s1);
  padding: 2px 7px;
  border-radius: var(--r1);
  font-size: 0.6875rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  white-space: nowrap;
  line-height: 1.5;
}
.tag-course { background: var(--course-bg); color: var(--course-color); }
.tag-lab    { background: var(--lab-bg);    color: var(--lab-color); }
.tag-cert   { background: var(--cert-bg);   color: var(--cert-color); }
.tag-path   { background: var(--path-bg);   color: var(--path-color); }
.tag-free   { background: var(--free-bg);   color: var(--free-color); }
.tag-pro    { background: var(--pro-bg);    color: var(--pro-color); }
.tag-soon   { background: var(--panel-bg-2); color: var(--text-helper); border: 1px solid var(--border); }
.tag-new    { background: var(--info-bg);   color: var(--blue-700); }

/* Difficulty */
.diff {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--text-secondary);
}
.diff::before { content: ''; display: inline-block; width: 6px; height: 6px; border-radius: 50%; }
.diff-beginner::before     { background: var(--success); }
.diff-intermediate::before { background: var(--warning); }
.diff-advanced::before     { background: var(--error); }

/* Status pills */
.pill { display: inline-flex; align-items: center; gap: 5px; padding: 2px 8px; border-radius: var(--r1); font-size: 0.6875rem; font-weight: 600; }
.pill-available { background: var(--success-bg); color: var(--success); border: 1px solid var(--success-border); }
.pill-locked    { background: var(--panel-bg-2); color: var(--text-helper); border: 1px solid var(--border); }
.pill-soon      { background: var(--panel-bg-2); color: var(--text-disabled); border: 1px solid var(--border); }
.pill-active    { background: var(--info-bg); color: var(--blue-700); border: 1px solid var(--info-border); }
.pill-progress  { background: var(--warning-bg); color: var(--warning); border: 1px solid var(--warning-border); }

/* ── Forms ──────────────────────────────────────────────────── */
.field { margin-bottom: var(--s5); }
.field-label { display: block; font-size: 0.875rem; font-weight: 600; color: var(--text-primary); margin-bottom: 5px; }
.field-input {
  display: block; width: 100%;
  padding: 8px 12px;
  font-size: 0.875rem; font-family: inherit;
  color: var(--text-primary);
  background: var(--panel-bg);
  border: 1px solid var(--border-strong);
  border-radius: var(--r2);
  outline: none;
  transition: border-color 0.1s, box-shadow 0.1s;
}
.field-input:focus { border-color: var(--blue-600); box-shadow: 0 0 0 2px rgba(15,98,254,0.15); }
.field-input::placeholder { color: var(--text-disabled); }
.field-hint  { font-size: 0.75rem; color: var(--text-helper); margin-top: 4px; }
.field-error { font-size: 0.75rem; color: var(--error); margin-top: 4px; }

/* Search field */
.search-field {
  display: flex;
  align-items: center;
  gap: var(--s2);
  background: var(--panel-bg);
  border: 1px solid var(--border-strong);
  border-radius: var(--r2);
  padding: 7px 12px;
}
.search-field:focus-within { border-color: var(--blue-600); box-shadow: 0 0 0 2px rgba(15,98,254,0.12); }
.search-field input { border: none; outline: none; font-size: 0.875rem; color: var(--text-primary); background: transparent; flex: 1; font-family: inherit; }
.search-field input::placeholder { color: var(--text-disabled); }

/* ── Notifications ──────────────────────────────────────────── */
.notif {
  display: flex;
  align-items: flex-start;
  gap: var(--s3);
  padding: 12px 14px;
  border-radius: var(--r2);
  font-size: 0.875rem;
  line-height: 1.55;
  border-left: 3px solid;
}
.notif svg { flex-shrink: 0; margin-top: 1px; }
.notif-title { font-weight: 600; margin-bottom: 2px; }
.notif-info    { background: var(--info-bg);    border-left-color: var(--blue-600); color: #00439c; }
.notif-success { background: var(--success-bg); border-left-color: var(--success);  color: #044317; }
.notif-warning { background: var(--warning-bg); border-left-color: var(--warning);  color: #4d3800; }
.notif-error   { background: var(--error-bg);   border-left-color: var(--error);    color: #750e13; }

/* ── Panels ─────────────────────────────────────────────────── */
.panel {
  background: var(--panel-bg);
  border: 1px solid var(--border);
  border-radius: var(--r3);
}
.panel-header {
  padding: var(--s4) var(--s5);
  border-bottom: 1px solid var(--border);
  background: var(--panel-bg-2);
  border-radius: var(--r3) var(--r3) 0 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.panel-title { font-size: 0.875rem; font-weight: 600; color: var(--text-primary); }
.panel-body { padding: var(--s5); }
.panel-footer { padding: var(--s4) var(--s5); border-top: 1px solid var(--border); background: var(--panel-bg-2); border-radius: 0 0 var(--r3) var(--r3); }

/* ── Content cards ──────────────────────────────────────────── */
.card {
  background: var(--panel-bg);
  border: 1px solid var(--border);
  border-radius: var(--r3);
  display: flex;
  flex-direction: column;
  overflow: hidden;
  transition: border-color 0.15s;
}
.card:hover { border-color: var(--blue-400); }
.card.locked { opacity: 0.55; cursor: default; pointer-events: none; }
.card-accent { height: 3px; }
.accent-course { background: var(--blue-600); }
.accent-lab    { background: var(--teal-600); }
.accent-cert   { background: #b26800; }
.accent-path   { background: #6929c4; }
.card-body { padding: var(--s4) var(--s5); flex: 1; }
.card-meta { display: flex; align-items: center; gap: var(--s2); margin-bottom: var(--s3); flex-wrap: wrap; }
.card-title { font-size: 0.9375rem; font-weight: 600; color: var(--text-primary); line-height: 1.35; margin-bottom: var(--s2); }
.card-desc { font-size: 0.8125rem; color: var(--text-secondary); line-height: 1.6; }
.card-stats { display: flex; align-items: center; gap: var(--s4); font-size: 0.75rem; color: var(--text-helper); margin-top: var(--s3); flex-wrap: wrap; }
.card-footer { padding: var(--s3) var(--s5); border-top: 1px solid var(--border); background: var(--panel-bg-2); display: flex; align-items: center; justify-content: space-between; font-size: 0.8125rem; }

/* ── Progress bars ──────────────────────────────────────────── */
.prog-wrap { }
.prog-row { display: flex; justify-content: space-between; font-size: 0.75rem; color: var(--text-helper); margin-bottom: 4px; }
.prog-track { height: 4px; background: var(--border); border-radius: 999px; overflow: hidden; }
.prog-fill { height: 100%; background: var(--blue-600); border-radius: 999px; transition: width 0.4s; }
.prog-fill.success { background: var(--success); }

/* ── Course sidebar (training view) ─────────────────────────── */
.course-sidebar {
  width: var(--sidebar-w);
  background: var(--panel-bg);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  flex-shrink: 0;
  overflow: hidden;
}
.cs-head {
  padding: var(--s4) var(--s5);
  border-bottom: 1px solid var(--border);
  background: var(--panel-bg-2);
  flex-shrink: 0;
}
.cs-course-label { font-size: 0.625rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.07em; color: var(--text-helper); margin-bottom: 3px; }
.cs-level-name { font-size: 0.9375rem; font-weight: 600; color: var(--text-primary); line-height: 1.3; }
.cs-scroll { flex: 1; overflow-y: auto; scrollbar-width: thin; scrollbar-color: var(--border) transparent; }
.cs-scroll::-webkit-scrollbar { width: 3px; }
.cs-scroll::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }

/* Chapter rows */
.ch { border-bottom: 1px solid var(--border); }
.ch-head {
  display: flex;
  align-items: flex-start;
  gap: var(--s3);
  padding: var(--s3) var(--s4);
  cursor: pointer;
  background: var(--panel-bg-2);
  border-left: 3px solid transparent;
  transition: background 0.1s;
}
.ch-head:hover { background: var(--shell-bg); }
.ch-head.active { background: var(--info-bg); border-left-color: var(--blue-600); }
.ch-num {
  width: 20px; height: 20px;
  border-radius: 50%;
  border: 1.5px solid var(--border-strong);
  display: flex; align-items: center; justify-content: center;
  font-size: 9px; font-weight: 700;
  color: var(--text-helper);
  flex-shrink: 0; margin-top: 1px;
}
.ch-num.done { border-color: var(--success); background: var(--success); color: #fff; font-size: 8px; }
.ch-num.cur  { border-color: var(--blue-600); color: var(--blue-600); }
.ch-info { flex: 1; min-width: 0; }
.ch-label { font-size: 0.5625rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.07em; color: var(--text-helper); }
.ch-name { font-size: 0.8125rem; color: var(--text-secondary); line-height: 1.3; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.ch-head.active .ch-name { color: var(--text-primary); font-weight: 500; }
.ch-dots { display: flex; gap: 3px; margin-top: 4px; }
.ch-dot { width: 5px; height: 5px; border-radius: 50%; background: var(--border); }
.ch-dot.done { background: var(--success); }
.ch-dot.cur  { background: var(--blue-600); }
.ch-arr { color: var(--text-helper); font-size: 10px; flex-shrink: 0; margin-top: 3px; transition: transform 0.15s; }
.ch-arr.open { transform: rotate(90deg); }

/* Section list */
.ch-secs { display: none; background: var(--panel-bg); }
.ch-secs.open { display: block; }
.sec-link {
  display: flex;
  align-items: center;
  gap: var(--s2);
  padding: 6px var(--s4) 6px 30px;
  font-size: 0.8125rem;
  color: var(--text-secondary);
  text-decoration: none;
  border-left: 3px solid transparent;
  transition: background 0.1s;
  line-height: 1.35;
}
.sec-link:hover { background: var(--shell-bg); color: var(--text-primary); text-decoration: none; }
.sec-link.active { background: var(--info-bg); border-left-color: var(--blue-600); color: var(--blue-700); font-weight: 500; }
.sec-dot { width: 6px; height: 6px; border-radius: 50%; border: 1.5px solid var(--border-strong); flex-shrink: 0; }
.sec-dot.done { background: var(--success); border-color: var(--success); }
.sec-dot.cur  { border-color: var(--blue-600); }

.cs-foot {
  padding: var(--s3) var(--s4);
  border-top: 1px solid var(--border);
  background: var(--panel-bg-2);
  flex-shrink: 0;
}
.lang-strip { display: flex; gap: 3px; flex-wrap: wrap; }
.lang-btn {
  padding: 3px 7px;
  font-size: 0.6875rem; font-weight: 600;
  border: 1px solid var(--border-strong);
  border-radius: var(--r1);
  background: var(--panel-bg);
  color: var(--text-secondary);
  cursor: pointer;
  text-decoration: none;
  transition: all 0.1s;
}
.lang-btn:hover { border-color: var(--blue-600); color: var(--blue-600); text-decoration: none; }
.lang-btn.active { background: var(--blue-600); border-color: var(--blue-600); color: #fff; }

/* ── Breadcrumb bar ─────────────────────────────────────────── */
.crumb-bar {
  height: 36px;
  background: var(--panel-bg);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  padding: 0 var(--s5);
  gap: var(--s2);
  font-size: 0.8125rem;
  flex-shrink: 0;
}
.crumb { color: var(--text-helper); text-decoration: none; }
.crumb:hover { color: var(--blue-600); text-decoration: none; }
.crumb-sep { color: var(--border-strong); }
.crumb-cur { color: var(--text-secondary); }

/* ── Page header ────────────────────────────────────────────── */
.page-header {
  background: var(--nav-bg);
  padding: var(--s8) var(--s8) var(--s7);
  border-bottom: 1px solid rgba(255,255,255,0.06);
}
.page-header-inner { max-width: var(--page-max); margin: 0 auto; }
.page-eyebrow { font-size: 0.6875rem; font-weight: 600; text-transform: uppercase; letter-spacing: 0.07em; color: var(--blue-400); margin-bottom: var(--s2); }
.page-title { font-size: 1.75rem; font-weight: 600; color: #e4e8f0; letter-spacing: -0.02em; line-height: 1.2; margin-bottom: var(--s2); }
.page-subtitle { font-size: 0.9375rem; color: #7a92aa; line-height: 1.6; max-width: 560px; }
.page-stats { display: flex; gap: var(--s7); margin-top: var(--s5); padding-top: var(--s5); border-top: 1px solid rgba(255,255,255,0.07); flex-wrap: wrap; }
.page-stat strong { color: #c8d6e8; font-weight: 700; }
.page-stat { font-size: 0.8125rem; color: #6b7c93; }

/* ── Left filter sidebar ────────────────────────────────────── */
.filter-sidebar {
  width: var(--filter-w);
  background: var(--panel-bg);
  border-right: 1px solid var(--border);
  padding: var(--s5) var(--s4);
  flex-shrink: 0;
  overflow-y: auto;
  scrollbar-width: thin;
}
.filter-sidebar::-webkit-scrollbar { width: 3px; }
.filter-sidebar::-webkit-scrollbar-thumb { background: var(--border); }
.filter-group { margin-bottom: var(--s5); }
.filter-group-title {
  font-size: 0.6875rem; font-weight: 700;
  text-transform: uppercase; letter-spacing: 0.07em;
  color: var(--text-primary);
  margin-bottom: var(--s2);
  padding-bottom: var(--s2);
  border-bottom: 1px solid var(--border);
}
.filter-opt {
  display: flex; align-items: center; gap: var(--s2);
  padding: 5px var(--s2);
  border-radius: var(--r1);
  cursor: pointer;
  font-size: 0.875rem;
  color: var(--text-secondary);
  transition: background 0.1s;
  user-select: none;
  margin-bottom: 1px;
}
.filter-opt:hover { background: var(--shell-bg); color: var(--text-primary); }
.filter-opt.sel { background: var(--info-bg); color: var(--blue-700); font-weight: 500; }
.f-check {
  width: 14px; height: 14px;
  border: 1.5px solid var(--border-strong);
  border-radius: var(--r1);
  flex-shrink: 0;
  display: flex; align-items: center; justify-content: center;
}
.filter-opt.sel .f-check { background: var(--blue-600); border-color: var(--blue-600); }
.f-check-mark { display: none; }
.filter-opt.sel .f-check-mark { display: block; }
.f-count { margin-left: auto; font-size: 0.6875rem; color: var(--text-helper); }

/* ── Catalog grid ───────────────────────────────────────────── */
.card-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: var(--s4); }

/* ── Env specs ──────────────────────────────────────────────── */
.env-grid { display: grid; grid-template-columns: 1fr 1fr; gap: var(--s2); margin: var(--s4) 0; }
.env-item { display: flex; align-items: center; gap: var(--s2); padding: 7px 10px; background: var(--panel-bg-2); border: 1px solid var(--border); border-radius: var(--r1); font-size: 0.75rem; }
.env-label { color: var(--text-helper); }
.env-val { color: var(--text-primary); font-weight: 600; margin-left: auto; font-family: 'JetBrains Mono', monospace; font-size: 0.6875rem; }

/* ── Path step ──────────────────────────────────────────────── */
.path-step { display: flex; align-items: center; gap: var(--s3); padding: var(--s3); border: 1px solid var(--border); border-radius: var(--r2); font-size: 0.875rem; margin-bottom: var(--s2); background: var(--panel-bg); }
.path-step.done   { border-color: var(--success-border); background: var(--success-bg); }
.path-step.active { border-color: var(--info-border); background: var(--info-bg); }
.path-step.locked { opacity: 0.5; }
.ps-icon { width: 20px; height: 20px; border-radius: 50%; border: 1.5px solid var(--border-strong); display: flex; align-items: center; justify-content: center; flex-shrink: 0; }
.path-step.done   .ps-icon { background: var(--success); border-color: var(--success); }
.path-step.active .ps-icon { background: var(--blue-600); border-color: var(--blue-600); }
.ps-name { flex: 1; color: var(--text-secondary); }
.path-step.active .ps-name { color: var(--text-primary); font-weight: 500; }
.path-step.locked .ps-name { color: var(--text-disabled); }

/* ── Stage track ────────────────────────────────────────────── */
.stage-track { display: flex; position: relative; margin: var(--s5) 0; }
.stage-track::before { content: ''; position: absolute; top: 16px; left: 18px; right: 18px; height: 1px; background: var(--border); }
.stage-step { flex: 1; display: flex; flex-direction: column; align-items: center; gap: var(--s2); position: relative; z-index: 1; }
.stage-circle { width: 32px; height: 32px; border-radius: 50%; border: 1.5px solid var(--border-strong); background: var(--panel-bg); display: flex; align-items: center; justify-content: center; }
.stage-step.done   .stage-circle { border-color: var(--success); background: var(--success-bg); }
.stage-step.active .stage-circle { border-color: var(--blue-600); background: var(--info-bg); }
.stage-label { font-size: 0.5625rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.05em; color: var(--text-helper); text-align: center; }
.stage-step.done   .stage-label { color: var(--success); }
.stage-step.active .stage-label { color: var(--blue-600); }

/* ── Lesson reading ─────────────────────────────────────────── */
.reading-area { max-width: var(--content-max); margin: 0 auto; padding: var(--s10) var(--s10) var(--s16); }
.reading-area h1 { font-size: 1.625rem; font-weight: 600; color: var(--text-primary); margin-bottom: var(--s2); letter-spacing: -0.02em; line-height: 1.2; }
.reading-area h2 { font-size: 1.125rem; font-weight: 600; color: var(--text-primary); margin: var(--s10) 0 var(--s4); padding-top: var(--s8); border-top: 1px solid var(--border); }
.reading-area h2:first-of-type { border-top: none; padding-top: 0; margin-top: var(--s6); }
.reading-area h3 { font-size: 0.9375rem; font-weight: 700; color: var(--text-primary); margin: var(--s6) 0 var(--s3); }
.reading-area h4 { font-size: 0.875rem; font-weight: 600; color: var(--text-secondary); margin: var(--s5) 0 var(--s2); }
.reading-area p { font-size: 0.9375rem; line-height: 1.8; color: var(--text-secondary); margin-bottom: var(--s4); }
.reading-area hr { border: none; border-top: 1px solid var(--border); margin: var(--s8) 0; }
.reading-area strong { font-weight: 600; color: var(--text-primary); }
.reading-area em { font-style: italic; }
.reading-area code { font-family: 'JetBrains Mono', monospace; font-size: 0.82em; background: var(--panel-bg-2); color: #9d1939; padding: 1px 5px; border-radius: var(--r1); border: 1px solid var(--border); }
.reading-area ul { list-style: none; margin: var(--s2) 0 var(--s4); }
.reading-area ul li { font-size: 0.9375rem; line-height: 1.75; color: var(--text-secondary); padding: 2px 0 2px var(--s5); position: relative; }
.reading-area ul li::before { content: "–"; position: absolute; left: var(--s2); color: var(--text-helper); }

/* Code blocks */
.code-block { background: #13171f; border: 1px solid #252d3d; border-radius: var(--r3); overflow: hidden; margin: var(--s5) 0; }
.code-bar { display: flex; align-items: center; justify-content: space-between; padding: 7px 14px; background: #1a2030; border-bottom: 1px solid #252d3d; }
.code-lang { font-family: 'JetBrains Mono', monospace; font-size: 0.6875rem; font-weight: 500; color: #5c7a9a; letter-spacing: 0.05em; text-transform: uppercase; }
.code-block pre { padding: 16px; font-family: 'JetBrains Mono', monospace; font-size: 0.8125rem; line-height: 1.65; color: #c9d7e8; overflow-x: auto; tab-size: 2; }
.copy-btn { font-size: 0.6875rem; font-weight: 500; color: #5c7a9a; background: transparent; border: 1px solid #252d3d; border-radius: var(--r1); padding: 3px 8px; cursor: pointer; font-family: inherit; transition: all 0.1s; }
.copy-btn:hover { color: #c9d7e8; border-color: #3a5070; }

/* Callouts */
.callout { border-left: 3px solid; padding: var(--s4) var(--s5); margin: var(--s5) 0; border-radius: 0 var(--r2) var(--r2) 0; font-size: 0.875rem; line-height: 1.65; }
.callout-head { font-weight: 700; font-size: 0.6875rem; text-transform: uppercase; letter-spacing: 0.05em; margin-bottom: var(--s1); }
.callout-note    { background: var(--info-bg);    border-left-color: var(--blue-600); color: #00439c; }
.callout-tip     { background: var(--success-bg); border-left-color: var(--success);  color: #044317; }
.callout-warning { background: var(--warning-bg); border-left-color: var(--warning);  color: #4d3800; }
.callout-danger  { background: var(--error-bg);   border-left-color: var(--error);    color: #750e13; }

/* Tables in reading area */
.reading-area table { width: 100%; border-collapse: collapse; font-size: 0.875rem; margin: var(--s5) 0; border: 1px solid var(--border); border-radius: var(--r2); overflow: hidden; }
.reading-area thead th { background: var(--panel-bg-2); border-bottom: 1px solid var(--border-strong); padding: 9px 14px; text-align: left; font-size: 0.6875rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.05em; color: var(--text-primary); }
.reading-area tbody td { padding: 9px 14px; border-bottom: 1px solid var(--border); color: var(--text-secondary); vertical-align: top; }
.reading-area tbody tr:last-child td { border-bottom: none; }
.reading-area tbody tr:hover td { background: var(--panel-bg-2); }

/* Section nav */
.sec-nav { display: flex; justify-content: space-between; align-items: center; padding-top: var(--s8); margin-top: var(--s10); border-top: 1px solid var(--border); }
.sec-nav-card { display: flex; flex-direction: column; padding: var(--s4); border: 1px solid var(--border); border-radius: var(--r2); text-decoration: none; max-width: 240px; background: var(--panel-bg); transition: border-color 0.15s; }
.sec-nav-card:hover { border-color: var(--blue-500); text-decoration: none; }
.sec-nav-dir { font-size: 0.6875rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.05em; color: var(--text-helper); margin-bottom: 3px; }
.sec-nav-title { font-size: 0.875rem; font-weight: 600; color: var(--text-primary); }
.sec-nav-card.next-card { background: var(--blue-600); border-color: var(--blue-600); text-align: right; }
.sec-nav-card.next-card .sec-nav-dir { color: rgba(255,255,255,0.6); }
.sec-nav-card.next-card .sec-nav-title { color: #fff; }
.sec-nav-card.next-card:hover { background: var(--blue-700); border-color: var(--blue-700); }

/* ── Data table ─────────────────────────────────────────────── */
.data-table { width: 100%; border-collapse: collapse; font-size: 0.875rem; }
.data-table th { background: var(--panel-bg-2); border-bottom: 1px solid var(--border-strong); padding: 9px 14px; text-align: left; font-size: 0.6875rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.05em; color: var(--text-primary); }
.data-table td { padding: 9px 14px; border-bottom: 1px solid var(--border); color: var(--text-secondary); vertical-align: middle; }
.data-table tr:last-child td { border-bottom: none; }
.data-table tr:hover td { background: var(--panel-bg-2); }

/* ── App shell ──────────────────────────────────────────────── */
.app-shell { display: flex; flex-direction: column; height: 100vh; overflow: hidden; padding-top: var(--nav-h); }
.app-body  { display: flex; flex: 1; overflow: hidden; }
.app-main  { flex: 1; display: flex; flex-direction: column; overflow: hidden; background: var(--shell-bg); }
.app-scroll { flex: 1; overflow-y: auto; }

/* Read progress strip */
.read-prog { height: 2px; background: var(--border); flex-shrink: 0; }
.read-prog-fill { height: 100%; background: var(--blue-600); width: 0%; transition: width 0.1s; }

/* ── Auth shell ─────────────────────────────────────────────── */
.auth-shell { min-height: 100vh; background: var(--shell-bg); display: flex; flex-direction: column; }
.auth-topbar { height: var(--nav-h); background: var(--nav-bg); border-bottom: 1px solid var(--nav-border); display: flex; align-items: center; padding: 0 var(--s8); }
.auth-body { flex: 1; display: flex; align-items: center; justify-content: center; padding: var(--s12) var(--s6); }
.auth-card { background: var(--panel-bg); border: 1px solid var(--border); border-radius: var(--r4); padding: var(--s8) var(--s10); width: 100%; max-width: 400px; box-shadow: var(--e2); }

/* ── Responsive ─────────────────────────────────────────────── */
@media (max-width: 1024px) {
  .course-sidebar { display: none; }
  .filter-sidebar  { display: none; }
  .reading-area { padding: var(--s6) var(--s5) var(--s12); }
}
@media (max-width: 768px) {
  :root { --page-max: 100%; }
  .nav-items { display: none; }
  .card-grid { grid-template-columns: 1fr; }
  .page-header { padding: var(--s6) var(--s4) var(--s5); }
  .auth-card { padding: var(--s6); }
}