:root {
  --bg: #071019;
  --panel: #0d1822;
  --panel-2: #111f2b;
  --panel-3: #162734;
  --text: #eef6f8;
  --muted: #8ba0ad;
  --line: #203441;
  --cyan: #23e4c6;
  --cyan-soft: rgba(35, 228, 198, .12);
  --blue: #49a8ff;
  --amber: #ffc857;
  --red: #ff6b78;
  --green: #68e399;
  --radius: 16px;
  --mono: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; background: radial-gradient(circle at 75% -10%, #133242 0, transparent 34%), var(--bg); color: var(--text); font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif; min-height: 100vh; }
button, input, select { font: inherit; }
button { cursor: pointer; }
.skip-link { position: fixed; left: 1rem; top: -5rem; z-index: 100; background: var(--cyan); color: #03110f; padding: .75rem 1rem; border-radius: 8px; font-weight: 800; }
.skip-link:focus { top: 1rem; }
.shell { min-height: 100vh; }
.sidebar { position: fixed; inset: 0 auto 0 0; width: 248px; padding: 26px 18px; border-right: 1px solid var(--line); background: rgba(7, 16, 25, .94); backdrop-filter: blur(18px); display: flex; flex-direction: column; z-index: 20; }
.brand { color: var(--text); text-decoration: none; display: flex; gap: 12px; align-items: center; padding: 0 8px 28px; border-bottom: 1px solid var(--line); }
.brand-mark { display: grid; place-items: center; width: 44px; height: 44px; border: 1px solid var(--cyan); color: var(--cyan); font-family: var(--mono); font-size: 13px; font-weight: 800; clip-path: polygon(11% 0, 100% 0, 100% 89%, 89% 100%, 0 100%, 0 11%); }
.brand strong, .brand small { display: block; }
.brand strong { font-size: 14px; letter-spacing: .12em; }
.brand small { color: var(--muted); font-size: 10px; margin-top: 3px; }
.nav-list { display: grid; gap: 7px; margin-top: 26px; }
.nav-item { border: 0; background: transparent; color: var(--muted); text-align: left; padding: 12px 10px; border-radius: 9px; font-size: 13px; font-weight: 650; transition: .2s ease; }
.nav-item span { font: 10px var(--mono); margin-right: 9px; color: #506674; }
.nav-item:hover { color: var(--text); background: rgba(255,255,255,.035); }
.nav-item.active { color: var(--cyan); background: var(--cyan-soft); }
.nav-item.active span { color: var(--cyan); }
.sidebar-status { margin-top: auto; padding: 16px 8px 0; border-top: 1px solid var(--line); display: flex; gap: 10px; align-items: center; }
.status-dot { width: 8px; height: 8px; border-radius: 50%; background: var(--cyan); box-shadow: 0 0 14px var(--cyan); }
.sidebar-status strong, .sidebar-status small { display: block; }
.sidebar-status strong { font: 10px var(--mono); color: var(--cyan); letter-spacing: .08em; }
.sidebar-status small { color: var(--muted); font-size: 9px; margin-top: 4px; }
main { margin-left: 248px; }
.topbar { height: 68px; border-bottom: 1px solid var(--line); display: flex; align-items: center; justify-content: space-between; padding: 0 38px; position: sticky; top: 0; z-index: 15; background: rgba(7, 16, 25, .86); backdrop-filter: blur(16px); }
.breadcrumb { color: var(--muted); font: 10px var(--mono); letter-spacing: .1em; }
.breadcrumb span { color: #536a77; }
.level-pill { padding: 7px 11px; border: 1px solid #265043; color: var(--cyan); border-radius: 999px; font: 11px var(--mono); }
.mobile-menu { display: none; border: 0; background: transparent; color: var(--text); font-size: 20px; }
.view { display: none; max-width: 1280px; margin: 0 auto; padding: 38px; animation: enter .25s ease; }
.view.active { display: block; }
@keyframes enter { from { opacity: 0; transform: translateY(6px); } }
.panel { background: linear-gradient(145deg, rgba(17,31,43,.95), rgba(11,24,34,.95)); border: 1px solid var(--line); border-radius: var(--radius); box-shadow: 0 22px 60px rgba(0,0,0,.18); }
.hero { min-height: 330px; padding: 48px; display: grid; grid-template-columns: 1.4fr .8fr; gap: 30px; overflow: hidden; position: relative; }
.hero::after { content: ""; position: absolute; width: 260px; height: 260px; right: -80px; bottom: -100px; border: 1px solid rgba(35,228,198,.15); border-radius: 50%; box-shadow: 0 0 0 40px rgba(35,228,198,.025), 0 0 0 80px rgba(35,228,198,.015); }
.eyebrow { color: var(--cyan); margin: 0 0 9px; font: 700 10px var(--mono); letter-spacing: .15em; }
h1, h2, p { margin-top: 0; }
.hero h1, .page-title h1 { letter-spacing: -.045em; line-height: 1.02; }
.hero h1 { font-size: clamp(36px, 5vw, 62px); margin: 14px 0 18px; max-width: 800px; }
.hero h1 span { color: var(--cyan); }
.hero p:not(.eyebrow) { color: var(--muted); line-height: 1.65; max-width: 640px; font-size: 15px; }
.primary-action, .secondary-action { border-radius: 8px; font-weight: 800; padding: 12px 16px; transition: .2s ease; }
.primary-action { border: 1px solid var(--cyan); background: var(--cyan); color: #031410; }
.primary-action:hover { transform: translateY(-1px); box-shadow: 0 9px 28px rgba(35,228,198,.18); }
.primary-action:focus-visible, button:focus-visible, input:focus-visible, select:focus-visible { outline: 2px solid var(--cyan); outline-offset: 2px; }
.secondary-action { border: 1px solid var(--line); color: var(--text); background: transparent; }
.secondary-action:hover { border-color: var(--cyan); color: var(--cyan); }
.hero-topology { align-self: center; justify-self: center; width: 260px; padding: 20px; position: relative; z-index: 1; }
.mini-node { padding: 9px 12px; border: 1px solid var(--line); border-radius: 7px; background: #0b1720; text-align: center; font: 10px var(--mono); letter-spacing: .08em; }
.mini-node.hmc { color: var(--blue); border-color: #285681; }
.mini-node.vios { color: var(--cyan); border-color: #276054; flex: 1; }
.mini-node.lpar { color: var(--amber); border-color: #65552c; }
.connector.vertical { width: 1px; height: 17px; background: var(--line); margin: auto; }
.split-line { height: 13px; border: solid var(--line); border-width: 1px 1px 0; margin: 0 48px; }
.mini-row { display: flex; gap: 8px; }
.metric-grid { display: grid; grid-template-columns: 1.15fr repeat(3, 1fr); gap: 14px; margin-top: 14px; }
.metric { padding: 20px; min-height: 108px; display: flex; align-items: center; gap: 14px; position: relative; }
.metric-icon { width: 34px; height: 34px; border-radius: 9px; display: grid; place-items: center; color: var(--cyan); background: var(--cyan-soft); font-family: var(--mono); }
.metric small, .metric strong { display: block; }
.metric small { color: var(--muted); font: 9px var(--mono); letter-spacing: .08em; margin-bottom: 5px; }
.metric strong { font-size: 24px; }
.progress-track { position: absolute; bottom: 0; left: 0; right: 0; height: 3px; background: rgba(255,255,255,.03); border-radius: 0 0 var(--radius) var(--radius); overflow: hidden; }
.progress-track i { display: block; height: 100%; width: 0; background: var(--cyan); transition: width .5s ease; }
.dashboard-grid { display: grid; grid-template-columns: .8fr 1.2fr; gap: 14px; margin-top: 14px; }
.next-module, .readiness { padding: 26px; }
.section-heading { display: flex; justify-content: space-between; align-items: flex-start; gap: 16px; }
.section-heading h2 { font-size: 19px; margin: 0; }
.next-module > p { color: var(--muted); line-height: 1.6; min-height: 50px; }
.module-meta { display: flex; gap: 8px; color: #6f8794; font: 10px var(--mono); margin: 24px 0 15px; }
.difficulty { display: inline-flex; align-items: center; align-self: flex-start; padding: 5px 8px; border-radius: 5px; font: 700 9px var(--mono); letter-spacing: .08em; }
.difficulty.beginner { color: var(--green); background: rgba(104,227,153,.1); }
.difficulty.intermediate { color: var(--amber); background: rgba(255,200,87,.1); }
.difficulty.advanced { color: #c493ff; background: rgba(196,147,255,.1); }
.readiness-row { display: grid; grid-template-columns: 90px 1fr 36px; gap: 10px; align-items: center; margin-top: 14px; }
.readiness-row span { font-size: 11px; color: var(--muted); }
.readiness-row b { font: 10px var(--mono); text-align: right; color: #6f8794; }
.readiness-track { height: 5px; background: #0a141c; border-radius: 5px; overflow: hidden; }
.readiness-track i { display: block; height: 100%; background: linear-gradient(90deg, var(--blue), var(--cyan)); border-radius: inherit; }
.text-action { border: 0; background: transparent; color: var(--muted); margin-top: 18px; font-size: 11px; padding: 7px 0; }
.text-action:hover { color: var(--text); }
.text-action.danger:hover { color: var(--red); }
.page-title { display: flex; align-items: flex-end; justify-content: space-between; gap: 20px; margin-bottom: 26px; }
.page-title h1 { font-size: clamp(32px, 4vw, 48px); margin: 6px 0 8px; }
.page-title > div > p:last-child { color: var(--muted); margin: 0; }
.learn-layout { display: grid; grid-template-columns: 250px 1fr; gap: 16px; align-items: start; }
.topic-rail { padding: 15px; position: sticky; top: 84px; }
.topic-rail label { display: block; color: var(--muted); font: 9px var(--mono); letter-spacing: .08em; margin: 2px 3px 8px; }
input, select { border: 1px solid var(--line); background: #0a151e; color: var(--text); border-radius: 7px; padding: 10px 11px; font-size: 12px; min-width: 0; }
input::placeholder { color: #506572; }
.topic-rail input { width: 100%; }
#topic-list { display: grid; gap: 5px; margin-top: 12px; }
.topic-button { border: 0; background: transparent; color: var(--muted); display: grid; grid-template-columns: 26px 1fr auto; gap: 8px; align-items: center; text-align: left; padding: 10px 8px; border-radius: 8px; font-size: 11px; }
.topic-button:hover { background: rgba(255,255,255,.035); color: var(--text); }
.topic-button.active { background: var(--cyan-soft); color: var(--cyan); }
.topic-button .topic-no { font: 9px var(--mono); color: #536975; }
.topic-button .done { color: var(--green); }
.lesson-column { display: grid; gap: 16px; }
.lesson-card, .diagram-card, .command-card, .flashcard-card { padding: clamp(22px, 4vw, 34px); }
.lesson-head { display: flex; justify-content: space-between; gap: 16px; }
.lesson-head h2 { font-size: 30px; margin: 0 0 20px; }
.lesson-lead { font-size: 17px; line-height: 1.65; color: #c8d7dd; }
.analogy { margin: 22px 0; padding: 16px 18px; border-left: 2px solid var(--cyan); background: var(--cyan-soft); color: #bcece3; font-size: 13px; line-height: 1.6; }
.lesson-body { display: grid; gap: 18px; }
.lesson-block h3 { font-size: 13px; letter-spacing: .02em; margin-bottom: 8px; }
.lesson-block p, .lesson-block li { color: var(--muted); font-size: 13px; line-height: 1.7; }
.lesson-block ul { margin: 0; padding-left: 18px; }
.live-label { font: 9px var(--mono); color: var(--cyan); white-space: nowrap; }
.live-label i { display: inline-block; width: 6px; height: 6px; border-radius: 50%; background: var(--cyan); box-shadow: 0 0 8px var(--cyan); margin-right: 5px; }
.diagram-card > p { color: var(--muted); font-size: 12px; }
.diagram { min-height: 145px; padding: 18px; border: 1px solid var(--line); border-radius: 10px; background: #08131b; display: flex; align-items: center; justify-content: center; gap: 0; overflow-x: auto; }
.diagram-node { border: 1px solid #2b4655; background: #10202b; color: #d8e6eb; border-radius: 8px; min-width: 104px; padding: 14px 12px; text-align: center; font: 700 10px var(--mono); transition: .2s ease; }
button.diagram-node:hover, button.diagram-node.active { color: var(--cyan); border-color: var(--cyan); background: var(--cyan-soft); transform: translateY(-2px); }
.diagram-arrow { width: 48px; min-width: 35px; height: 1px; background: linear-gradient(90deg, #29414f, var(--cyan)); position: relative; }
.diagram-arrow::after { content: ""; position: absolute; right: -1px; top: -3px; width: 7px; height: 7px; border-top: 1px solid var(--cyan); border-right: 1px solid var(--cyan); transform: rotate(45deg); }
.diagram-detail { min-height: 42px; color: #b6c8cf; border-top: 1px solid var(--line); margin-top: 18px; padding-top: 15px; font-size: 12px; line-height: 1.6; }
.filter-row { display: grid; grid-template-columns: 1fr 150px 150px; gap: 8px; margin-top: 20px; }
.command-list { display: grid; gap: 8px; margin-top: 14px; }
.command-item { border: 1px solid var(--line); border-radius: 9px; overflow: hidden; }
.command-trigger { width: 100%; display: grid; grid-template-columns: minmax(150px, .7fr) 1fr auto; align-items: center; gap: 14px; border: 0; background: #0a151e; color: var(--text); padding: 14px; text-align: left; }
.command-trigger:hover { background: #0d1b25; }
.command-trigger code { color: var(--cyan); font: 12px var(--mono); word-break: break-word; }
.command-trigger span { color: var(--muted); font-size: 11px; }
.command-trigger b { color: #5f7581; font: 10px var(--mono); }
.command-detail { display: none; padding: 14px; border-top: 1px solid var(--line); background: #101e28; color: var(--muted); font-size: 12px; line-height: 1.6; }
.command-item.open .command-detail { display: block; }
.command-detail strong { color: var(--text); }
.empty-state { color: var(--muted); padding: 28px; text-align: center; font-size: 12px; }
.flashcard { display: block; width: 100%; min-height: 210px; border: 1px solid #2d524e; border-radius: 12px; background: radial-gradient(circle at 50% 120%, rgba(35,228,198,.15), transparent 60%), #0a171f; color: var(--text); padding: 28px; text-align: center; position: relative; }
.flashcard:hover { border-color: var(--cyan); }
.flash-label { display: block; color: var(--cyan); font: 9px var(--mono); letter-spacing: .12em; margin-bottom: 24px; }
.flashcard strong { display: block; font-size: clamp(19px, 3vw, 28px); line-height: 1.35; max-width: 700px; margin: auto; }
.flashcard #flash-answer { display: none; color: #c7d7dd; font-size: 15px; line-height: 1.7; max-width: 700px; margin: 18px auto 0; }
.flashcard.flipped #flash-answer { display: block; }
.flashcard.flipped #flash-question { color: var(--muted); font-size: 14px; }
.flash-actions { display: flex; justify-content: center; gap: 8px; margin-top: 12px; }
.flash-actions button, #new-practice { border: 1px solid var(--line); background: transparent; color: var(--muted); padding: 9px 12px; border-radius: 7px; font-size: 11px; }
.flash-actions button:hover, #new-practice:hover { color: var(--cyan); border-color: var(--cyan); }
.practice-score { text-align: right; }
.practice-score span, .practice-score strong { display: block; }
.practice-score span { color: var(--muted); font: 9px var(--mono); }
.practice-score strong { color: var(--cyan); font-size: 30px; }
.practice-controls { padding: 14px; display: flex; justify-content: space-between; gap: 16px; margin-bottom: 16px; }
.segmented { display: flex; background: #07131b; border-radius: 8px; padding: 4px; }
.segmented button { border: 0; background: transparent; color: var(--muted); padding: 8px 13px; border-radius: 6px; font-size: 11px; font-weight: 700; }
.segmented button.active { background: var(--cyan-soft); color: var(--cyan); }
.filter-row.compact { display: flex; margin: 0; }
.challenge-panel { padding: clamp(24px, 5vw, 46px); min-height: 510px; }
.challenge-meta { display: flex; gap: 8px; align-items: center; color: #6d8490; font: 9px var(--mono); letter-spacing: .08em; }
.challenge-meta > span:first-child { color: var(--cyan); background: var(--cyan-soft); padding: 5px 8px; border-radius: 5px; }
.challenge-panel h2 { font-size: clamp(23px, 3vw, 34px); line-height: 1.35; max-width: 900px; margin: 28px 0; }
.option-list { display: grid; gap: 10px; max-width: 900px; }
.option { border: 1px solid var(--line); border-radius: 9px; background: #0a151e; color: #c9d7dc; padding: 14px 16px; text-align: left; display: flex; gap: 12px; align-items: flex-start; line-height: 1.45; }
.option-key { flex: 0 0 auto; width: 23px; height: 23px; border: 1px solid #34505e; border-radius: 5px; display: grid; place-items: center; color: var(--muted); font: 10px var(--mono); }
.option:hover:not(:disabled) { border-color: var(--cyan); color: var(--text); }
.option.correct { border-color: var(--green); background: rgba(104,227,153,.08); color: var(--green); }
.option.incorrect { border-color: var(--red); background: rgba(255,107,120,.08); color: var(--red); }
.option:disabled { cursor: default; }
.feedback { display: none; max-width: 900px; margin: 18px 0; padding: 14px 16px; border-radius: 8px; font-size: 12px; line-height: 1.65; }
.feedback.show { display: block; }
.feedback.good { color: #aef1c7; background: rgba(104,227,153,.08); border: 1px solid rgba(104,227,153,.22); }
.feedback.bad { color: #ffc0c6; background: rgba(255,107,120,.08); border: 1px solid rgba(255,107,120,.22); }
.scenario-brief { color: var(--muted); line-height: 1.65; max-width: 900px; }
.terminal { border: 1px solid #263b47; border-radius: 9px; background: #050b10; overflow: hidden; max-width: 900px; margin: 22px 0; }
.terminal-bar { height: 34px; background: #0c1720; display: flex; align-items: center; gap: 6px; padding: 0 12px; border-bottom: 1px solid #1d303b; }
.terminal-bar i { width: 7px; height: 7px; border-radius: 50%; background: #3f5662; }
.terminal-bar i:first-child { background: var(--red); }
.terminal-bar i:nth-child(2) { background: var(--amber); }
.terminal-bar i:nth-child(3) { background: var(--green); }
.terminal-bar span { margin-left: 7px; color: #5d7480; font: 9px var(--mono); }
.terminal pre { margin: 0; padding: 18px; color: #91dfcf; font: 12px/1.65 var(--mono); white-space: pre-wrap; }
.decision-label { color: var(--text); font-size: 12px; font-weight: 750; }
.hidden { display: none !important; }
.toast { position: fixed; right: 24px; bottom: 24px; max-width: 330px; padding: 13px 15px; background: #12232d; border: 1px solid #2c4d4d; color: #dbe9ed; border-radius: 9px; font-size: 12px; box-shadow: 0 16px 50px rgba(0,0,0,.35); transform: translateY(30px); opacity: 0; pointer-events: none; transition: .25s ease; z-index: 50; }
.toast.show { opacity: 1; transform: translateY(0); }

@media (max-width: 980px) {
  .sidebar { transform: translateX(-100%); transition: transform .25s ease; }
  .sidebar.open { transform: translateX(0); box-shadow: 20px 0 60px rgba(0,0,0,.4); }
  main { margin-left: 0; }
  .mobile-menu { display: block; }
  .topbar { padding: 0 20px; }
  .metric-grid { grid-template-columns: repeat(2, 1fr); }
  .learn-layout { grid-template-columns: 1fr; }
  .topic-rail { position: static; }
  #topic-list { grid-template-columns: repeat(3, 1fr); }
}
@media (max-width: 680px) {
  .view { padding: 22px 15px; }
  .breadcrumb { display: none; }
  .hero { grid-template-columns: 1fr; padding: 28px 24px; }
  .hero-topology { width: 100%; }
  .metric-grid, .dashboard-grid { grid-template-columns: 1fr; }
  .page-title { align-items: flex-start; flex-direction: column; }
  .page-title .primary-action { width: 100%; }
  #topic-list { grid-template-columns: 1fr 1fr; }
  .diagram { justify-content: flex-start; }
  .filter-row { grid-template-columns: 1fr; }
  .command-trigger { grid-template-columns: 1fr auto; }
  .command-trigger span { grid-column: 1 / -1; }
  .practice-controls { flex-direction: column; }
  .filter-row.compact { display: grid; grid-template-columns: 1fr; }
  .filter-row.compact select, .filter-row.compact button { width: 100%; }
  .challenge-panel { min-height: 560px; }
}
@media (prefers-reduced-motion: reduce) { *, *::before, *::after { scroll-behavior: auto !important; animation: none !important; transition: none !important; } }