:root {
  --bg-primary: #1a1a2e;
  --bg-secondary: #151521;
  --bg-code: #0d1117;
  --bg-info: rgba(55,138,221,0.08);
  --text-primary: #e8eaed;
  --text-secondary: #9aa0a6;
  --text-tertiary: #5f6368;
  --text-info: #6aafff;
  --border: #2a2a3e;
  --border-info: rgba(55,138,221,0.25);
  --accent: #378ADD;
  --accent-bg: #1a2a44;
  --accent-text: #6aafff;
  --green: #1D9E75;
  --green-bg: rgba(29,158,117,0.1);
  /* Topic categories */
  --cat-ai: #378ADD;
  --cat-ai-bg: rgba(55,138,221,0.10);
  --cat-agents: #a78bfa;
  --cat-agents-bg: rgba(167,139,250,0.10);
  --cat-robotics: #f97316;
  --cat-robotics-bg: rgba(249,115,22,0.10);
  --cat-coming: #5f6368;
  --cat-coming-bg: rgba(95,99,104,0.08);
  --radius: 10px;
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', 'Consolas', monospace;
}
* { box-sizing: border-box; margin: 0; padding: 0; }
body { font-family: var(--font-sans); background: var(--bg-primary); color: var(--text-primary); -webkit-font-smoothing: antialiased; }
a { color: var(--accent-text); text-decoration: none; }
a:hover { text-decoration: underline; }
code { font-family: var(--font-mono); font-size: 0.88em; background: rgba(255,255,255,0.06); padding: 2px 6px; border-radius: 4px; }

.page { display: grid; grid-template-columns: 260px 1fr; min-height: 100vh; }
@media (max-width: 768px) { .page { grid-template-columns: 1fr; } .sidebar { display: none; } }

.sidebar { background: var(--bg-secondary); border-right: 1px solid var(--border); padding: 1.5rem 0; position: sticky; top: 0; height: 100vh; overflow-y: auto; display: flex; flex-direction: column; }
.sidebar-logo { padding: 0 1.25rem 1.5rem; font-size: 18px; font-weight: 600; color: var(--text-primary); }
.sidebar-title { font-size: 13px; font-weight: 600; color: var(--text-tertiary); text-transform: uppercase; letter-spacing: 0.08em; padding: 14px 1.25rem 6px; }
.nav-item { display: flex; align-items: center; gap: 8px; font-size: 16px; padding: 8px 1.25rem; color: var(--text-secondary); cursor: pointer; border-left: 2px solid transparent; transition: all 0.15s; text-decoration: none; }
.nav-item:hover { color: var(--text-primary); background: rgba(255,255,255,0.03); text-decoration: none; }
.nav-item.active { color: var(--accent-text); border-left-color: var(--accent); background: var(--bg-info); }
.nav-item .num { display: inline-flex; align-items: center; justify-content: center; width: 20px; height: 20px; border-radius: 50%; border: 1px solid var(--border); font-size: 11px; color: var(--text-tertiary); flex-shrink: 0; }
.nav-item.active .num { border-color: var(--accent); color: var(--accent-text); background: var(--accent-bg); }
.nav-item.done .num { border-color: var(--green); color: var(--green); background: var(--green-bg); }

/* Collapsible tutorial sections */
.sidebar-section { }
.sidebar-section-header { display: flex; align-items: center; justify-content: space-between; padding: 14px 1.25rem 6px; cursor: pointer; user-select: none; }
.sidebar-section-header:hover .sidebar-title { color: var(--text-secondary); }
.sidebar-section-header .sidebar-title { margin: 0; padding: 0; }
.sidebar-chevron { font-size: 10px; color: var(--text-tertiary); transition: transform 0.2s; }
.sidebar-section.collapsed .sidebar-chevron { transform: rotate(-90deg); }
.sidebar-section.collapsed .sidebar-section-body { display: none; }

/* Quick links separator */
.sidebar-divider { height: 1px; background: var(--border); margin: 10px 1.25rem; }

.sidebar-bottom { margin-top: auto; padding-top: 1rem; border-top: 1px solid var(--border); }
.sidebar-user { display: block; font-size: 14px; color: var(--text-tertiary); padding: 0 1.25rem 0.5rem; }

.content { padding: 2.5rem 3rem; max-width: 820px; overflow: auto; }

.progress { display: flex; align-items: center; gap: 4px; margin-bottom: 2rem; }
.prog-step { display: flex; align-items: center; justify-content: center; width: 28px; height: 28px; border-radius: 50%; font-size: 11px; font-weight: 600; border: 2px solid var(--border); color: var(--text-tertiary); transition: all 0.2s; }
.prog-step.done { border-color: var(--green); color: var(--green); background: var(--green-bg); }
.prog-step.active { border-color: var(--accent); color: var(--accent-text); background: var(--accent-bg); }
.prog-line { flex: 1; height: 2px; background: var(--border); max-width: 32px; min-width: 16px; }
.prog-line.done { background: var(--green); }

.step-badge { display: inline-flex; align-items: center; gap: 6px; font-size: 13px; font-weight: 500; color: var(--accent-text); background: var(--accent-bg); padding: 4px 12px; border-radius: 99px; margin-bottom: 12px; }
.step-dot { width: 6px; height: 6px; border-radius: 50%; background: var(--accent); }

h1 { font-size: 32px; font-weight: 600; color: var(--text-primary); margin-bottom: 8px; }
h2 { font-size: 22px; font-weight: 600; color: var(--text-primary); margin: 2.5rem 0 0.8rem; }
.subtitle { font-size: 16px; color: var(--text-secondary); margin-bottom: 2rem; line-height: 1.7; }
.prose { font-size: 16px; color: var(--text-secondary); line-height: 1.75; margin-bottom: 1.25rem; }
.prose strong { color: var(--text-primary); }

.code-block { background: var(--bg-code); border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden; margin: 1rem 0 1.5rem; }
.code-header { display: flex; align-items: center; justify-content: space-between; padding: 8px 14px; border-bottom: 1px solid rgba(255,255,255,0.06); }
.code-lang { font-size: 12px; font-weight: 500; color: #5a6270; font-family: var(--font-mono); }
.copy-btn { display: flex; align-items: center; gap: 5px; font-size: 12px; color: #6a737d; background: rgba(255,255,255,0.05); border: 1px solid rgba(255,255,255,0.1); border-radius: 6px; padding: 4px 10px; cursor: pointer; font-family: var(--font-sans); }
.copy-btn:hover { background: rgba(255,255,255,0.1); color: #c8d0db; }
.copy-btn.copied { color: var(--green); border-color: rgba(29,158,117,0.3); }
.code-body { padding: 16px; font-family: var(--font-mono); font-size: 15px; line-height: 1.7; color: #c8d0db; white-space: pre; overflow-x: auto; }

.callout { display: flex; gap: 12px; background: var(--bg-info); border: 1px solid var(--border-info); border-radius: var(--radius); padding: 14px 16px; margin: 1rem 0 1.5rem; }
.callout-icon { flex-shrink: 0; margin-top: 1px; font-size: 16px; }
.callout-text { font-size: 15px; color: var(--text-info); line-height: 1.65; }
.callout.warning { background: rgba(250,204,21,0.06); border-color: rgba(250,204,21,0.2); }
.callout.warning .callout-text { color: #facc15; }
.callout.success { background: var(--green-bg); border-color: rgba(29,158,117,0.25); }
.callout.success .callout-text { color: #5dcaa5; }
.callout.danger { background: rgba(239,68,68,0.06); border-color: rgba(239,68,68,0.2); }
.callout.danger .callout-text { color: #f87171; }

table { width: 100%; border-collapse: collapse; margin: 1rem 0 1.5rem; font-size: 15px; }
th, td { text-align: left; padding: 10px 14px; border: 1px solid var(--border); }
th { background: var(--bg-secondary); color: var(--text-primary); font-weight: 500; font-size: 14px; }
td { color: var(--text-secondary); }
td code { font-size: 13px; }

.nav-buttons { display: flex; justify-content: space-between; align-items: center; margin-top: 3rem; padding-top: 2rem; border-top: 1px solid var(--border); }
.nav-right { display: flex; align-items: center; gap: 12px; }
.next-btn { display: inline-flex; align-items: center; gap: 6px; font-size: 15px; font-weight: 500; color: var(--accent-text); background: var(--accent-bg); border: 1px solid rgba(55,138,221,0.3); border-radius: var(--radius); padding: 10px 20px; cursor: pointer; text-decoration: none; transition: all 0.15s; }
.next-btn:hover { background: rgba(55,138,221,0.15); border-color: var(--accent); text-decoration: none; }
.next-btn.disabled { opacity: 0.3; pointer-events: none; cursor: default; }
.prev-btn { display: inline-flex; align-items: center; gap: 6px; font-size: 15px; font-weight: 500; color: var(--accent-text); background: var(--accent-bg); border: 1px solid rgba(55,138,221,0.3); border-radius: var(--radius); padding: 10px 20px; text-decoration: none; transition: all 0.15s; }
.prev-btn:hover { background: rgba(55,138,221,0.15); border-color: var(--accent); text-decoration: none; }

ul, ol { margin: 0.5rem 0 1rem 1.5rem; font-size: 16px; color: var(--text-secondary); }
li { margin-bottom: 0.4rem; line-height: 1.6; }

/* Login page */
.login-page { display: flex; align-items: center; justify-content: center; min-height: 100vh; }
.login-box { background: var(--bg-secondary); border: 1px solid var(--border); border-radius: 16px; padding: 2.5rem; width: 100%; max-width: 380px; }
.login-logo { font-size: 22px; font-weight: 700; text-align: center; margin-bottom: 4px; background: linear-gradient(135deg, #60a5fa, #a78bfa); -webkit-background-clip: text; -webkit-text-fill-color: transparent; }
.login-sub { text-align: center; font-size: 14px; color: var(--text-tertiary); margin-bottom: 1.5rem; }
.login-error { background: rgba(239,68,68,0.1); border: 1px solid rgba(239,68,68,0.3); border-radius: 8px; padding: 10px 14px; font-size: 14px; color: #f87171; margin-bottom: 1rem; }
.login-box input { display: block; width: 100%; background: var(--bg-primary); border: 1px solid var(--border); border-radius: 8px; padding: 10px 14px; font-size: 15px; color: var(--text-primary); margin-bottom: 0.8rem; font-family: var(--font-sans); outline: none; }
.login-box input:focus { border-color: var(--accent); }
.login-box button { display: block; width: 100%; background: var(--accent); border: none; border-radius: 8px; padding: 10px; font-size: 15px; font-weight: 500; color: #fff; cursor: pointer; font-family: var(--font-sans); margin-top: 0.5rem; }
.login-box button:hover { background: #2a7acc; }

/* Home page */
.home-content { padding: 3rem; max-width: 800px; }
.home-title { font-size: 30px; font-weight: 700; margin-bottom: 8px; }
.home-sub { font-size: 16px; color: var(--text-secondary); margin-bottom: 2.5rem; line-height: 1.6; }
.tutorial-card { display: block; background: var(--bg-secondary); border: 1px solid var(--border); border-radius: var(--radius); padding: 1.5rem; margin-bottom: 1rem; transition: all 0.15s; text-decoration: none; }
.tutorial-card:hover { border-color: var(--accent); transform: translateY(-1px); text-decoration: none; }
.tutorial-card h2 { font-size: 18px; margin: 0 0 6px; color: var(--text-primary); }
.tutorial-card p { font-size: 15px; color: var(--text-secondary); line-height: 1.6; margin: 0 0 10px; }
.tutorial-meta { display: flex; gap: 8px; flex-wrap: wrap; }
.tutorial-tag { font-size: 12px; padding: 3px 10px; border-radius: 99px; background: var(--accent-bg); color: var(--accent-text); }
.tutorial-tag.green { background: var(--green-bg); color: #5dcaa5; }
.tutorial-tag.blue { background: rgba(59,130,246,0.1); color: #60a5fa; }
.tutorial-tag.progress-tag { background: rgba(168,85,247,0.1); color: #c084fc; }
.section-label { font-size: 11px; font-weight: 600; color: var(--text-tertiary); text-transform: uppercase; letter-spacing: 0.08em; margin: 2rem 0 0.8rem; }
.tool-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 0.8rem; }
.tool-card { display: block; background: var(--bg-secondary); border: 1px solid var(--border); border-radius: var(--radius); padding: 1rem; text-align: center; text-decoration: none; transition: all 0.15s; }
.tool-card:hover { border-color: var(--accent); text-decoration: none; }
.tool-card h3 { font-size: 14px; color: var(--text-primary); margin-bottom: 3px; }
.tool-card p { font-size: 12px; color: var(--text-tertiary); }

/* Admin */
.add-user-form { display: flex; gap: 0.5rem; margin-bottom: 2rem; flex-wrap: wrap; }
.add-user-form input { background: var(--bg-secondary); border: 1px solid var(--border); border-radius: 8px; padding: 8px 12px; font-size: 14px; color: var(--text-primary); font-family: var(--font-sans); outline: none; }
.add-user-form input:focus { border-color: var(--accent); }

/* Mark complete button */
.complete-btn { display: inline-flex; align-items: center; gap: 6px; font-size: 15px; font-weight: 500; color: #f87171; background: rgba(239,68,68,0.08); border: 1px solid rgba(239,68,68,0.3); border-radius: var(--radius); padding: 10px 20px; cursor: pointer; font-family: var(--font-sans); transition: all 0.15s; }
.complete-btn:hover { background: rgba(239,68,68,0.15); }
.complete-btn.done { color: #5dcaa5; background: var(--green-bg); border-color: rgba(29,158,117,0.3); cursor: default; }

/* Config panel */
.config-panel { background: var(--bg-secondary); border: 1px solid var(--border); border-radius: var(--radius); margin-bottom: 2rem; overflow: hidden; }
.config-header { display: flex; align-items: center; justify-content: space-between; padding: 10px 16px; border-bottom: 1px solid var(--border); }
.config-header span { font-size: 13px; font-weight: 500; color: var(--text-secondary); }
.config-toggle { font-size: 12px; color: var(--accent-text); background: var(--accent-bg); border: 1px solid rgba(55,138,221,0.3); border-radius: 6px; padding: 4px 12px; cursor: pointer; font-family: var(--font-sans); }
.config-toggle:hover { background: rgba(55,138,221,0.15); }
.config-body { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; padding: 14px 16px; }
.config-field { display: flex; flex-direction: column; gap: 4px; }
.config-field label { font-size: 11px; font-weight: 500; color: var(--text-tertiary); text-transform: uppercase; letter-spacing: 0.05em; }
.config-field input { background: var(--bg-primary); border: 1px solid var(--border); border-radius: 6px; padding: 7px 10px; font-size: 14px; color: var(--text-primary); font-family: var(--font-mono); outline: none; }
.config-field input:focus { border-color: var(--accent); }
.config-field.full { grid-column: 1 / -1; }
/* Highlighted variant: yellow border + tint, used when the user MUST fill in values */
.config-panel.highlight { border: 2px solid #facc15; background: rgba(250,204,21,0.08); box-shadow: 0 0 0 4px rgba(250,204,21,0.08); }
.config-panel.highlight .config-header { border-bottom-color: rgba(250,204,21,0.4); }
.config-panel.highlight .config-header span { color: #facc15; font-weight: 600; }

/* --- Help modal --- */
.help-modal {
  position: fixed; inset: 0; background: rgba(0,0,0,0.7);
  display: flex; align-items: center; justify-content: center;
  z-index: 1000;
}
.help-modal-inner {
  background: #1e1e1e; border: 1px solid #444; border-radius: 10px;
  width: min(560px, 92vw); max-height: 86vh; overflow: auto;
  padding: 20px;
}
.help-modal-header { display: flex; justify-content: space-between; align-items: center; }
.help-modal-header h3 { margin: 0; font-size: 20px; }
.help-close { background: none; border: none; color: #ccc; font-size: 24px; cursor: pointer; }
.help-modal-body textarea {
  width: 100%; background: #111; color: #eee; border: 1px solid #444;
  border-radius: 6px; padding: 10px; font-family: inherit; font-size: 14px;
}
.help-hint { color: #aaa; font-size: 13px; margin: 8px 0 12px; }
.help-actions { display: flex; align-items: center; gap: 12px; margin-top: 10px; }
.help-send {
  background: #4c8; color: #111; border: none; padding: 8px 14px;
  border-radius: 6px; cursor: pointer; font-weight: 600;
}
.help-send:hover { background: #5dc; }
#help-status { color: #aaa; font-size: 13px; }
.help-config-preview { margin-top: 14px; color: #aaa; font-size: 12px; }
.help-config-preview pre {
  background: #111; padding: 8px; border-radius: 4px;
  max-height: 200px; overflow: auto;
}

/* --- Checkpoint badge --- */
.checkpoint-area {
  margin: 24px 0; padding: 14px 16px; border-radius: 8px;
  background: linear-gradient(90deg, #2a2a1e 0%, #1e1e1e 100%);
  border-left: 4px solid #fc4;
}
.checkpoint-flag { font-size: 18px; margin-right: 8px; }
.checkpoint-area h4 { margin: 0 0 4px; font-size: 15px; color: #fc4; }
.checkpoint-area p { margin: 0 0 10px; font-size: 13px; color: #ccc; }
.checkpoint-btn {
  background: #fc4; color: #111; border: none; padding: 6px 12px;
  border-radius: 4px; cursor: pointer; font-weight: 600; font-size: 13px;
}
.checkpoint-btn.set { background: #4c8; }
.checkpoint-btn:hover { opacity: 0.85; }
.checkpoint-note-input {
  margin-left: 8px; padding: 5px 8px; background: #111; color: #eee;
  border: 1px solid #444; border-radius: 4px; font-size: 13px;
}

/* ── Topic categories (sidebar + home page) ─────────────────────── */

/* Sidebar: category header above its sections */
.sidebar-cat-header { display: flex; align-items: center; gap: 8px; padding: 18px 1.25rem 4px; border-top: 1px solid var(--border); margin-top: 6px; }
.sidebar-cat-header:first-of-type, .sidebar-logo + .sidebar-cat-header { border-top: none; margin-top: 0; }
.sidebar-cat-header .cat-icon { font-size: 14px; line-height: 1; }
.sidebar-cat-header .cat-label { font-size: 11px; font-weight: 700; text-transform: uppercase; letter-spacing: 0.1em; }
.sidebar-cat-header.cat-ai .cat-label { color: var(--cat-ai); }
.sidebar-cat-header.cat-agents .cat-label { color: var(--cat-agents); }
.sidebar-cat-header.cat-robotics .cat-label { color: var(--cat-robotics); }
.sidebar-cat-header.cat-coming .cat-label { color: var(--cat-coming); }

/* Sidebar: colored stripe on each section header to keep category visible when collapsed */
.sidebar-section.cat-ai .sidebar-section-header { box-shadow: inset 3px 0 0 var(--cat-ai); }
.sidebar-section.cat-agents .sidebar-section-header { box-shadow: inset 3px 0 0 var(--cat-agents); }
.sidebar-section.cat-robotics .sidebar-section-header { box-shadow: inset 3px 0 0 var(--cat-robotics); }

/* Home page: category block — boxed container that visually groups its banner + cards */
.category-block { margin: 2rem 0; background: var(--bg-secondary); border: 1px solid var(--border); border-top-width: 4px; border-radius: var(--radius); padding: 0 1.25rem 1.25rem; overflow: hidden; }
.category-block.cat-ai       { border-top-color: var(--cat-ai); }
.category-block.cat-agents   { border-top-color: var(--cat-agents); }
.category-block.cat-robotics { border-top-color: var(--cat-robotics); }
.category-block.cat-coming   { border-top-color: var(--cat-coming); }

/* Banner becomes the header inside the box: no own border/bg, just a bottom separator */
.category-banner { display: flex; align-items: flex-start; gap: 14px; padding: 18px 0 16px; margin: 0 -0.25rem 1rem; border-bottom: 1px solid var(--border); }
.category-banner .category-icon { font-size: 26px; line-height: 1; flex-shrink: 0; margin-top: 2px; }
.category-title { font-size: 18px; font-weight: 700; margin: 0 0 4px; }
.category-desc { font-size: 14px; color: var(--text-secondary); margin: 0; line-height: 1.55; }
.category-block.cat-ai       .category-title { color: var(--cat-ai); }
.category-block.cat-agents   .category-title { color: var(--cat-agents); }
.category-block.cat-robotics .category-title { color: var(--cat-robotics); }
.category-block.cat-coming   .category-title { color: var(--cat-coming); }

/* Subhead inside a category (e.g. "Beginner path" / "Detailed path") */
.category-subhead { font-size: 11px; font-weight: 600; color: var(--text-tertiary); text-transform: uppercase; letter-spacing: 0.08em; margin: 1.4rem 0 0.4rem; padding-left: 2px; }
.category-block .category-subhead:first-of-type { margin-top: 0.4rem; }

/* Tutorial cards INSIDE a category-block: flatten into items (no own card chrome) */
.category-block .tutorial-card { background: transparent; border: 1px solid transparent; border-left-width: 3px; border-radius: 6px; padding: 14px 16px; margin-bottom: 12px; transition: background 0.15s, border-color 0.15s, transform 0.15s; }
.category-block .tutorial-card:hover { background: rgba(255,255,255,0.03); transform: none; }
.category-block .tutorial-card h2 { font-size: 18px; margin: 0 0 6px; color: #bdc2c8; font-weight: 600; }
.category-block .tutorial-card p { font-size: 14px; margin: 0 0 10px; line-height: 1.55; }
.category-block .tutorial-card.cat-ai       { border-left-color: var(--cat-ai); }
.category-block .tutorial-card.cat-agents   { border-left-color: var(--cat-agents); }
.category-block .tutorial-card.cat-robotics { border-left-color: var(--cat-robotics); }
.category-block .tutorial-card.cat-ai:hover       { border-color: rgba(55,138,221,0.4);  border-left-color: var(--cat-ai); }
.category-block .tutorial-card.cat-agents:hover   { border-color: rgba(167,139,250,0.4); border-left-color: var(--cat-agents); }
.category-block .tutorial-card.cat-robotics:hover { border-color: rgba(249,115,22,0.4);  border-left-color: var(--cat-robotics); }

/* Home page: coming-soon placeholder cards */
.coming-soon-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 0.8rem; }
.coming-soon-card { display: flex; align-items: flex-start; gap: 10px; background: var(--bg-secondary); border: 1px dashed var(--border); border-radius: var(--radius); padding: 14px; opacity: 0.7; }
.coming-soon-card .coming-icon { font-size: 22px; line-height: 1; flex-shrink: 0; margin-top: 2px; opacity: 0.8; }
.coming-soon-card h3 { font-size: 14px; color: var(--text-secondary); margin: 0 0 3px; font-weight: 600; }
.coming-soon-card p { font-size: 12px; color: var(--text-tertiary); margin: 0; line-height: 1.5; }