/* MongoDB Mastery — styles */
:root {
  --bg: #0b1117;
  --bg2: #111a22;
  --panel: #142029;
  --panel2: #18262f;
  --border: #22333f;
  --text: #dbe7ee;
  --muted: #8aa1af;
  --faint: #7a909d;
  --green: #00ed64;
  --green2: #00b44c;
  --leaf: #13aa52;
  --blue: #38bdf8;
  --purple: #a78bfa;
  --orange: #f59e0b;
  --red: #f87171;
  --pink: #f472b6;
  --code-bg: #0a141b;
  --shadow: 0 8px 30px rgba(0, 0, 0, .35);
  --radius: 10px;
  --mono: 'JetBrains Mono', 'SF Mono', Menlo, Consolas, monospace;
  --sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Inter, Roboto, sans-serif;
}
[data-theme="light"] {
  --bg: #f6f8f7;
  --bg2: #eef3f1;
  --panel: #ffffff;
  --panel2: #f3f7f5;
  --border: #d8e2de;
  --text: #11221c;
  --muted: #4f6560;
  --faint: #5d706a;
  --green: #00a650;
  --green2: #00843f;
  --code-bg: #0f1d24;
  --shadow: 0 6px 24px rgba(16, 40, 30, .08);
}
* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body { background: var(--bg); color: var(--text); font: 15px/1.6 var(--sans); -webkit-font-smoothing: antialiased; }
a { color: var(--green); text-decoration: none; }
a:hover { text-decoration: underline; }
code, pre, kbd { font-family: var(--mono); }
:not(pre) > code { background: var(--panel2); border: 1px solid var(--border); border-radius: 5px; padding: 1px 5px; font-size: .88em; }
kbd { background: var(--panel2); border: 1px solid var(--border); border-bottom-width: 2px; border-radius: 4px; padding: 0 5px; font-size: .8em; }
.btn.primary kbd { background: rgba(0, 0, 0, .14); border-color: rgba(0, 0, 0, .22); color: inherit; }
h1, h2, h3, h4 { line-height: 1.25; margin: 1.4em 0 .5em; }
h1 { font-size: 2rem; margin-top: .2em; }
h2 { font-size: 1.45rem; }
h3 { font-size: 1.15rem; }
table { border-collapse: collapse; width: 100%; margin: 12px 0; font-size: .92rem; }
th, td { border: 1px solid var(--border); padding: 7px 10px; text-align: left; vertical-align: top; }
th { background: var(--panel2); font-weight: 600; }
button { font: inherit; cursor: pointer; }
.hidden { display: none !important; }

/* ---------- header ---------- */
.topbar { position: sticky; top: 0; z-index: 50; display: flex; align-items: center; gap: 18px; padding: 10px 22px; background: color-mix(in srgb, var(--bg) 88%, transparent); backdrop-filter: blur(10px); border-bottom: 1px solid var(--border); }
.brand { display: flex; align-items: center; gap: 10px; font-weight: 700; color: var(--text); font-size: 1.05rem; white-space: nowrap; }
.brand:hover { text-decoration: none; }
.brand .leaf { width: 26px; height: 26px; }
.brand small { color: var(--muted); font-weight: 500; }
.nav { display: flex; gap: 2px; flex-wrap: wrap; flex: 1; }
.nav a { color: var(--muted); padding: 6px 11px; border-radius: 8px; font-size: .92rem; font-weight: 500; }
.nav a:hover { color: var(--text); background: var(--panel); text-decoration: none; }
.nav a.active { color: var(--green); background: color-mix(in srgb, var(--green) 10%, transparent); }
.top-actions { display: flex; gap: 8px; align-items: center; }
.icon-btn { background: var(--panel); border: 1px solid var(--border); color: var(--text); border-radius: 8px; padding: 6px 10px; font-size: .88rem; display: inline-flex; gap: 6px; align-items: center; }
.icon-btn:hover { border-color: var(--green2); }
.menu-toggle { display: none; }

/* ---------- layout ---------- */
main { min-height: calc(100vh - 120px); }
.wrap { max-width: 1180px; margin: 0 auto; padding: 28px 24px 60px; }
.wrap.wide { max-width: 1440px; }
.foot { border-top: 1px solid var(--border); color: var(--faint); font-size: .85rem; padding: 18px 24px; text-align: center; }
.grid { display: grid; gap: 16px; }
.g2 { grid-template-columns: repeat(2, 1fr); }
.g3 { grid-template-columns: repeat(3, 1fr); }
.g4 { grid-template-columns: repeat(4, 1fr); }
.card { background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius); padding: 18px; }
.card h3 { margin-top: 0; }
.card.link { color: var(--text); display: block; transition: transform .12s, border-color .12s; }
.card.link:hover { transform: translateY(-2px); border-color: var(--green2); text-decoration: none; }
.muted { color: var(--muted); }
.faint { color: var(--faint); }
.pill { display: inline-block; border-radius: 999px; padding: 1px 10px; font-size: .76rem; font-weight: 600; border: 1px solid var(--border); color: var(--muted); }
.pill.lvl { color: #0b1014; border: none; font-weight: 600; }
.btn { display: inline-flex; align-items: center; gap: 7px; border-radius: 8px; padding: 8px 15px; font-weight: 600; border: 1px solid var(--border); background: var(--panel2); color: var(--text); font-size: .9rem; }
.btn:hover { border-color: var(--green2); text-decoration: none; }
.btn.primary { background: var(--green); color: #001e2b; border-color: var(--green); }
.btn.primary:hover { background: var(--green2); border-color: var(--green2); }
.btn.small { padding: 4px 10px; font-size: .8rem; }
.btn.danger { color: var(--red); }
.btn:disabled { opacity: .5; cursor: not-allowed; }
.row { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; }
.spacer { flex: 1; }

/* ---------- home ---------- */
.hero { display: grid; grid-template-columns: 1.15fr .85fr; gap: 36px; align-items: center; padding: 30px 0 20px; }
.hero h1 { font-size: 2.6rem; margin: 0 0 12px; letter-spacing: -.02em; }
.hero h1 span { color: var(--green); }
.hero p.lead { font-size: 1.12rem; color: var(--muted); max-width: 620px; }
.hero-term { background: var(--code-bg); border: 1px solid var(--border); border-radius: 12px; box-shadow: var(--shadow); overflow: hidden; }
.hero-term .bar { display: flex; gap: 6px; padding: 9px 12px; background: #0f1d24; border-bottom: 1px solid #1d2f38; }
.hero-term .bar i { width: 10px; height: 10px; border-radius: 50%; background: #2c3f49; }
.hero-term pre { margin: 0; padding: 14px 16px; color: #cfe3ea; font-size: .82rem; line-height: 1.55; }
.stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 14px; margin: 26px 0; }
.stat { background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius); padding: 14px 16px; }
.stat b { display: block; font-size: 1.7rem; color: var(--green); }
.stat span { color: var(--muted); font-size: .88rem; }
.level-strip { display: grid; grid-template-columns: repeat(7, 1fr); gap: 10px; }
.level-tile { border-radius: var(--radius); padding: 14px; background: var(--panel); border: 1px solid var(--border); border-top: 3px solid var(--c); color: var(--text); }
.level-tile:hover { text-decoration: none; border-color: var(--c); }
.level-tile b { display: block; margin-bottom: 4px; }
.level-tile small { color: var(--muted); font-size: .8rem; line-height: 1.4; display: block; }

/* ---------- curriculum ---------- */
.level-block { margin-bottom: 30px; }
.level-head { display: flex; align-items: center; gap: 12px; margin-bottom: 12px; }
.level-head h2 { margin: 0; }
.level-num { width: 34px; height: 34px; border-radius: 9px; display: grid; place-items: center; font-weight: 800; color: #04140c; }
.module-card { background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius); padding: 14px 16px; }
.module-card h4 { margin: 0 0 4px; font-size: 1rem; }
.module-card p { margin: 0 0 8px; color: var(--muted); font-size: .86rem; }
.lesson-link { display: flex; align-items: center; gap: 8px; padding: 5px 0; color: var(--text); font-size: .9rem; border-top: 1px dashed var(--border); }
.lesson-link:hover { color: var(--green); text-decoration: none; }
.check { width: 16px; height: 16px; border-radius: 50%; border: 2px solid var(--faint); flex-shrink: 0; display: inline-grid; place-items: center; font-size: 10px; }
.check.done { background: var(--green); border-color: var(--green); color: #001e2b; }
.progressbar { height: 6px; border-radius: 4px; background: var(--panel2); overflow: hidden; }
.progressbar > i { display: block; height: 100%; background: var(--green); }
.path-tabs { display: flex; gap: 8px; flex-wrap: wrap; margin: 10px 0 22px; }
.path-tabs button { background: var(--panel); border: 1px solid var(--border); color: var(--muted); border-radius: 999px; padding: 6px 14px; font-size: .86rem; }
.path-tabs button.on { color: #001e2b; background: var(--green); border-color: var(--green); font-weight: 600; }

/* ---------- lesson ---------- */
.lesson-layout { display: grid; grid-template-columns: 270px minmax(0, 1fr); gap: 30px; max-width: 1340px; margin: 0 auto; padding: 22px 24px 60px; }
.side-nav { position: sticky; top: 70px; align-self: start; max-height: calc(100vh - 90px); overflow: auto; font-size: .86rem; padding-right: 6px; }
.side-nav h5 { margin: 14px 0 4px; font-size: .74rem; letter-spacing: .06em; text-transform: uppercase; color: var(--faint); }
.side-nav a { display: flex; gap: 7px; align-items: center; color: var(--muted); padding: 4px 8px; border-radius: 6px; }
.side-nav a:hover { color: var(--text); background: var(--panel); text-decoration: none; }
.side-nav a.cur { color: var(--green); background: color-mix(in srgb, var(--green) 10%, transparent); }
.lesson { max-width: 880px; }
.lesson .crumbs { color: var(--faint); font-size: .85rem; }
.lesson .meta { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; margin: 6px 0 18px; }
.lesson .summary { font-size: 1.08rem; color: var(--muted); }
.objectives { background: var(--panel); border: 1px solid var(--border); border-left: 3px solid var(--green); border-radius: var(--radius); padding: 12px 18px; }
.objectives ul { margin: 6px 0; padding-left: 20px; }
.sec { margin: 26px 0; }
.sec > h2 { display: flex; align-items: center; gap: 10px; font-size: 1.25rem; border-bottom: 1px solid var(--border); padding-bottom: 6px; }
.sec > h2 .tag { font-size: .7rem; font-weight: 700; letter-spacing: .06em; text-transform: uppercase; padding: 2px 8px; border-radius: 5px; }
.tag.concept { background: rgba(56, 189, 248, .14); color: var(--blue); }
.tag.why { background: rgba(0, 237, 100, .12); color: var(--green); }
.tag.use { background: rgba(167, 139, 250, .14); color: var(--purple); }
.tag.internals { background: rgba(245, 158, 11, .14); color: var(--orange); }
.tag.mistakes { background: rgba(248, 113, 113, .14); color: var(--red); }
.tag.examples { background: rgba(244, 114, 182, .14); color: var(--pink); }
.tag.security { background: rgba(52, 211, 153, .14); color: var(--green); }
.avoid-pair { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; margin: 12px 0 18px; }
.avoid-col { border: 1px solid var(--border); border-radius: var(--radius); padding: 10px 12px; background: var(--panel); min-width: 0; }
.avoid-col.bad { border-top: 3px solid var(--red); }
.avoid-col.good { border-top: 3px solid var(--green); }
.avoid-col b { font-size: .8rem; text-transform: uppercase; letter-spacing: .06em; }
.avoid-col.bad b { color: var(--red); }
.avoid-col.good b { color: var(--green); }
.avoid-col pre { margin: 6px 0 0; padding: 0; background: none; border: 0; font: .82rem/1.5 var(--mono); white-space: pre-wrap; word-break: break-word; }
.avoid-why { grid-column: 1 / -1; margin: 0; color: var(--muted); font-size: .92rem; }
.challenge { background: var(--panel); border: 1px dashed var(--border); border-radius: var(--radius); padding: 12px 16px; }
@media (max-width: 860px) { .avoid-pair { grid-template-columns: 1fr; } }
.callout { border-radius: var(--radius); padding: 12px 16px; margin: 14px 0; border: 1px solid var(--border); background: var(--panel); }
.callout.tip { border-left: 3px solid var(--green); }
.callout.warn { border-left: 3px solid var(--orange); }
.callout.danger { border-left: 3px solid var(--red); }
.callout.info { border-left: 3px solid var(--blue); }
.callout b:first-child { display: block; margin-bottom: 2px; }
.lesson-nav { display: flex; justify-content: space-between; gap: 12px; margin-top: 36px; padding-top: 18px; border-top: 1px solid var(--border); }
.complete-bar { display: flex; align-items: center; gap: 12px; padding: 14px 18px; border-radius: var(--radius); background: var(--panel); border: 1px solid var(--border); margin-top: 26px; }

/* ---------- code ---------- */
.code { position: relative; background: var(--code-bg); border: 1px solid #1d2f38; border-radius: var(--radius); margin: 12px 0; overflow: hidden; }
.code .code-head { display: flex; align-items: center; gap: 8px; padding: 6px 10px; border-bottom: 1px solid #1d2f38; background: #0f1d24; font-size: .8rem; color: #8fb0bd; }
.code .code-head .title { flex: 1; font-weight: 600; }
.code pre { margin: 0; padding: 12px 14px; overflow: auto; color: #d6e6ec; font-size: .84rem; line-height: 1.55; }
.code .note { padding: 8px 14px; font-size: .85rem; color: #9fb8c3; border-top: 1px solid #1d2f38; background: #0d1a21; }
.code .out { border-top: 1px solid #1d2f38; max-height: 380px; overflow: auto; }
.code-btn { background: #17303b; color: #cfe6ef; border: 1px solid #23414d; border-radius: 6px; padding: 2px 9px; font-size: .76rem; }
.code-btn:hover { border-color: var(--green); color: var(--green); }
.code-btn.run { background: var(--green); color: #001e2b; border-color: var(--green); font-weight: 700; }
.tk-k { color: #c792ea; }
.tk-s { color: #a5e075; }
.tk-n { color: #f78c6c; }
.tk-c { color: #7d97a3; font-style: italic; }
.tk-o { color: #4fd6be; }
.tk-f { color: #82aaff; }
.tk-b { color: #ffcb6b; }

/* ---------- output console ---------- */
.console { font-family: var(--mono); font-size: .82rem; line-height: 1.5; padding: 10px 14px; color: #d6e6ec; background: var(--code-bg); }
.console .o { white-space: pre-wrap; word-break: break-word; margin: 0 0 8px; }
.console .o.print { color: #c4dbe4; }
.console .o.info { color: #7fa3b1; font-style: italic; }
.console .o.warn { color: #fbbf24; }
.console .o.error { color: #fca5a5; }
.console .meta { color: #5f7f8c; font-size: .74rem; }

/* ---------- playground ---------- */
.pg { display: grid; grid-template-columns: 250px minmax(0, 1fr); height: calc(100vh - 57px); }
.pg-side { border-right: 1px solid var(--border); background: var(--bg2); overflow: auto; padding: 12px; font-size: .86rem; }
.pg-side h5 { margin: 12px 0 6px; font-size: .72rem; letter-spacing: .06em; text-transform: uppercase; color: var(--faint); display: flex; align-items: center; }
.pg-side h5 .spacer { flex: 1; }
.tree-item { display: flex; align-items: center; gap: 6px; padding: 3px 6px; border-radius: 6px; cursor: pointer; color: var(--text); }
.tree-item:hover { background: var(--panel); }
.tree-item small { margin-left: auto; color: var(--faint); }
.tree-sub { padding-left: 18px; font-size: .8rem; color: var(--muted); }
.tree-sub div { padding: 1px 6px; cursor: pointer; border-radius: 5px; }
.tree-sub div:hover { background: var(--panel); color: var(--text); }
.snip { display: block; width: 100%; text-align: left; background: none; border: none; color: var(--muted); padding: 4px 6px; border-radius: 6px; font-size: .84rem; }
.snip:hover { background: var(--panel); color: var(--text); }
.pg-main { display: grid; grid-template-rows: auto minmax(160px, 42%) auto minmax(0, 1fr); min-width: 0; }
.pg-toolbar { display: flex; gap: 8px; align-items: center; padding: 8px 12px; border-bottom: 1px solid var(--border); background: var(--bg2); flex-wrap: wrap; }
.editor-wrap { position: relative; display: flex; background: var(--code-bg); min-height: 0; }
.gutter { padding: 12px 8px 12px 12px; text-align: right; color: #3f5a66; font: .86rem/1.55 var(--mono); user-select: none; white-space: pre; overflow: hidden; }
.editor { flex: 1; resize: none; border: none; outline: none; background: transparent; color: #e3f0f4; font: .86rem/1.55 var(--mono); padding: 12px 14px 12px 6px; tab-size: 2; white-space: pre; overflow: auto; caret-color: var(--green); }
.pg-tabs { display: flex; gap: 2px; padding: 0 10px; border-top: 1px solid var(--border); border-bottom: 1px solid var(--border); background: var(--bg2); }
.pg-tabs button { background: none; border: none; border-bottom: 2px solid transparent; color: var(--muted); padding: 8px 12px; font-size: .85rem; font-weight: 600; }
.pg-tabs button.on { color: var(--green); border-bottom-color: var(--green); }
.pg-tabs .status { margin-left: auto; align-self: center; font-size: .78rem; color: var(--faint); }
.pg-out { overflow: auto; min-height: 0; background: var(--code-bg); }
.pg-out .panel { padding: 14px; }
.resizer { height: 6px; cursor: row-resize; background: var(--border); }

/* ---------- explain tree ---------- */
.plan-summary { display: flex; gap: 10px; flex-wrap: wrap; margin-bottom: 14px; }
.metric { background: var(--panel); border: 1px solid var(--border); border-radius: 8px; padding: 8px 12px; min-width: 120px; }
.metric b { display: block; font-size: 1.25rem; }
.metric span { font-size: .75rem; color: var(--muted); text-transform: uppercase; letter-spacing: .04em; }
.metric.bad b { color: var(--red); }
.metric.good b { color: var(--green); }
.metric.warn b { color: var(--orange); }
.plan-tree { display: flex; flex-direction: column; align-items: flex-start; gap: 0; }
.stage { border: 1px solid var(--border); border-left: 4px solid var(--c, var(--blue)); background: var(--panel); border-radius: 8px; padding: 8px 12px; min-width: 260px; max-width: 640px; font-size: .84rem; color: var(--text); }
.stage .name { font-weight: 800; font-family: var(--mono); color: var(--c, var(--blue)); }
.stage .kv { color: var(--muted); font-family: var(--mono); font-size: .78rem; }
.stage-children { padding-left: 26px; border-left: 2px dashed var(--border); margin-left: 14px; display: flex; flex-direction: column; gap: 8px; padding-top: 8px; padding-bottom: 4px; }
.verdicts { margin: 14px 0 4px; padding: 0; list-style: none; }
.verdicts li { padding: 6px 10px; margin: 5px 0; border-radius: 6px; background: var(--panel); border: 1px solid var(--border); font-size: .86rem; }
.verdicts li.bad { border-left: 3px solid var(--red); }
.verdicts li.good { border-left: 3px solid var(--green); }
.verdicts li.warn { border-left: 3px solid var(--orange); }

/* ---------- pipeline stepper ---------- */
.pipe { display: flex; flex-direction: column; gap: 6px; }
.pipe-stage { background: var(--panel); border: 1px solid var(--border); border-radius: 8px; padding: 9px 12px; }
.pipe-stage .h { display: flex; gap: 10px; align-items: center; font-size: .86rem; }
.pipe-stage .h code { font-weight: 700; color: var(--green); background: none; border: none; }
.pipe-stage .bar { height: 6px; background: var(--panel2); border-radius: 4px; margin: 6px 0 2px; overflow: hidden; }
.pipe-stage .bar i { display: block; height: 100%; background: linear-gradient(90deg, var(--green2), var(--blue)); }
.pipe-stage pre { margin: 6px 0 0; font-size: .76rem; color: var(--muted); max-height: 220px; overflow: auto; background: var(--code-bg); padding: 8px; border-radius: 6px; }
.pipe-arrow { text-align: center; color: var(--faint); font-size: .8rem; line-height: 1; }

/* ---------- quiz / interview ---------- */
.quiz-q { background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius); padding: 14px 16px; margin: 12px 0; }
.quiz-q .opts { display: grid; gap: 6px; margin-top: 8px; }
.quiz-q label { display: flex; gap: 9px; align-items: flex-start; padding: 7px 10px; border: 1px solid var(--border); border-radius: 8px; cursor: pointer; font-size: .92rem; }
.quiz-q label:hover { border-color: var(--green2); }
.quiz-q label.right { border-color: var(--green); background: rgba(0, 237, 100, .08); }
.quiz-q label.wrong { border-color: var(--red); background: rgba(248, 113, 113, .08); }
.quiz-q .explain { margin-top: 8px; font-size: .9rem; color: var(--muted); }
details.qa { background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius); margin: 8px 0; }
details.qa summary { cursor: pointer; padding: 11px 14px; font-weight: 600; list-style: none; display: flex; gap: 10px; align-items: flex-start; }
details.qa summary::-webkit-details-marker { display: none; }
details.qa summary::before { content: '+'; color: var(--green); font-weight: 800; width: 14px; flex-shrink: 0; }
details.qa[open] summary::before { content: '\2212'; }
details.qa .ans { padding: 0 16px 12px 38px; color: var(--text); font-size: .93rem; }
details.qa .ans p:first-child { margin-top: 0; }
.qa-tags { margin-left: auto; display: flex; gap: 5px; flex-shrink: 0; }
.filters { display: flex; gap: 8px; flex-wrap: wrap; align-items: center; margin: 12px 0 18px; }
.filters input, .filters select { background: var(--panel); border: 1px solid var(--border); color: var(--text); border-radius: 8px; padding: 7px 10px; font: inherit; font-size: .9rem; }
.filters input { min-width: 260px; }

/* ---------- exercises ---------- */
.ex-layout { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.15fr); gap: 20px; max-width: 1440px; margin: 0 auto; padding: 22px 24px 50px; }
.ex-editor { background: var(--code-bg); border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden; }
.ex-editor textarea { width: 100%; min-height: 230px; border: none; outline: none; resize: vertical; background: transparent; color: #e3f0f4; font: .86rem/1.55 var(--mono); padding: 12px 14px; tab-size: 2; }
.ex-result { margin-top: 12px; }
.result-banner { border-radius: 8px; padding: 10px 14px; font-weight: 600; margin-bottom: 10px; }
.result-banner.ok { background: rgba(0, 237, 100, .12); color: var(--green); border: 1px solid rgba(0, 237, 100, .35); }
.result-banner.no { background: rgba(248, 113, 113, .1); color: var(--red); border: 1px solid rgba(248, 113, 113, .35); }
.ex-row { display: flex; align-items: center; gap: 10px; padding: 10px 14px; border-bottom: 1px solid var(--border); color: var(--text); }
.ex-row:hover { background: var(--panel); text-decoration: none; }
.ex-row .t { flex: 1; font-weight: 600; }
.diff { background: rgba(245, 158, 11, .14); color: var(--orange); }

/* ---------- simulators / diagrams ---------- */
.sim { background: var(--panel); border: 1px solid var(--border); border-radius: 12px; padding: 16px; margin: 16px 0; }
.sim h3 { margin-top: 0; }
.sim-controls { display: flex; gap: 8px; flex-wrap: wrap; margin: 10px 0; align-items: center; }
.sim-controls select, .sim-controls input { background: var(--panel2); border: 1px solid var(--border); color: var(--text); border-radius: 7px; padding: 6px 8px; font: inherit; font-size: .86rem; }
.nodes { display: flex; gap: 14px; flex-wrap: wrap; margin: 12px 0; }
.node { width: 180px; border-radius: 10px; border: 2px solid var(--border); padding: 10px; background: var(--bg2); position: relative; transition: all .25s; }
.node.primary { border-color: var(--green); box-shadow: 0 0 0 3px rgba(0, 237, 100, .12); }
.node.secondary { border-color: var(--blue); }
.node.down { opacity: .45; border-style: dashed; border-color: var(--red); }
.node.candidate { border-color: var(--orange); }
.node.arbiter { border-color: var(--purple); }
.node .role { font-weight: 800; font-size: .78rem; letter-spacing: .05em; text-transform: uppercase; }
.node .oplog { display: flex; gap: 3px; flex-wrap: wrap; margin-top: 8px; min-height: 18px; }
.node .op { width: 14px; height: 14px; border-radius: 3px; background: var(--green2); font-size: 8px; color: #001e2b; display: grid; place-items: center; font-weight: 700; }
.node .op.w1 { background: var(--orange); }
.node .op.rolled { background: var(--red); }
.node .btns { display: flex; gap: 4px; margin-top: 8px; flex-wrap: wrap; }
.log { font-family: var(--mono); font-size: .78rem; background: var(--code-bg); color: #bcd3dc; border-radius: 8px; padding: 10px; max-height: 220px; overflow: auto; }
.log div { margin-bottom: 3px; }
.log .t { color: #5f7f8c; }
.shards { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; margin: 12px 0; }
.shard { background: var(--bg2); border: 1px solid var(--border); border-radius: 10px; padding: 10px; }
.shard .chunks { display: flex; flex-wrap: wrap; gap: 3px; margin: 8px 0; min-height: 22px; }
.shard .chunk { min-width: 22px; height: 18px; border-radius: 3px; background: var(--blue); font-size: 9px; color: #001e2b; display: grid; place-items: center; padding: 0 3px; font-weight: 700; }
.shard .chunk.hot { background: var(--red); }
.shard .chunk.jumbo { background: var(--purple); outline: 2px solid var(--pink); }
.hbar { height: 10px; background: var(--panel2); border-radius: 5px; overflow: hidden; }
.hbar i { display: block; height: 100%; background: var(--blue); }
.diagram { background: var(--bg2); border: 1px solid var(--border); border-radius: 12px; padding: 14px; margin: 14px 0; overflow-x: auto; }
.diagram svg { display: block; max-width: 100%; height: auto; margin: 0 auto; }
.diagram .cap { text-align: center; color: var(--muted); font-size: .84rem; margin-top: 8px; }
.steps { display: grid; grid-template-columns: 280px 1fr; gap: 16px; }
.steps ol { margin: 0; padding-left: 20px; }
.steps li { padding: 5px 6px; border-radius: 6px; cursor: pointer; color: var(--muted); font-size: .9rem; }
.steps li.on { background: color-mix(in srgb, var(--green) 12%, transparent); color: var(--text); font-weight: 600; }
.box-hl { transition: all .25s; }

/* ---------- search modal ---------- */
.modal-bg { position: fixed; inset: 0; background: rgba(0, 0, 0, .55); z-index: 100; display: flex; align-items: flex-start; justify-content: center; padding-top: 10vh; }
.modal { width: min(720px, 92vw); background: var(--panel); border: 1px solid var(--border); border-radius: 14px; box-shadow: var(--shadow); overflow: hidden; }
.modal input { width: 100%; border: none; border-bottom: 1px solid var(--border); background: transparent; color: var(--text); font: inherit; font-size: 1.05rem; padding: 16px 18px; outline: none; }
.modal .results { max-height: 60vh; overflow: auto; }
.modal .res { display: block; padding: 10px 18px; border-bottom: 1px solid var(--border); color: var(--text); }
.modal .res:hover, .modal .res.sel { background: var(--panel2); text-decoration: none; }
.modal .res small { color: var(--muted); display: block; }
.modal .res .kind { float: right; }

/* ---------- misc ---------- */
.toc { columns: 2; font-size: .92rem; }
.kbd-hint { color: var(--faint); font-size: .8rem; }
.toast { position: fixed; bottom: 20px; right: 20px; background: var(--panel); border: 1px solid var(--green2); color: var(--text); padding: 10px 16px; border-radius: 10px; box-shadow: var(--shadow); z-index: 200; font-size: .9rem; }
.cheat h3 { margin-top: 0; color: var(--green); font-size: 1rem; }
.cheat pre { margin: 0; font-size: .8rem; background: var(--code-bg); color: #d6e6ec; padding: 10px; border-radius: 8px; overflow: auto; }
.kpi-row { display: flex; gap: 10px; flex-wrap: wrap; }

@media (max-width: 1100px) {
  .hero { grid-template-columns: 1fr; }
  .level-strip { grid-template-columns: repeat(4, 1fr); }
  .g4 { grid-template-columns: repeat(2, 1fr); }
  .ex-layout { grid-template-columns: 1fr; }
}
@media (max-width: 860px) {
  .nav { display: none; }
  .nav.open { display: flex; position: absolute; top: 56px; left: 0; right: 0; flex-direction: column; background: var(--bg); border-bottom: 1px solid var(--border); padding: 10px; }
  .menu-toggle { display: inline-flex; }
  .lesson-layout { grid-template-columns: 1fr; }
  .side-nav { display: none; }
  .g2, .g3, .stats { grid-template-columns: 1fr 1fr; }
  .level-strip { grid-template-columns: repeat(2, 1fr); }
  .pg { grid-template-columns: 1fr; height: auto; }
  .pg-side { display: none; }
  .steps { grid-template-columns: 1fr; }
  .shards { grid-template-columns: 1fr; }
}

/* ---------- versions ---------- */
.ver-pill { display: inline-block; border-radius: 999px; padding: 1px 9px; font-size: .74rem; font-weight: 600; color: var(--blue); border: 1px solid color-mix(in srgb, var(--blue) 45%, transparent); background: color-mix(in srgb, var(--blue) 10%, transparent); white-space: nowrap; }
a.ver-pill:hover { text-decoration: none; border-color: var(--blue); }
.timeline { border-left: 2px solid var(--border); margin: 10px 0 0 8px; padding-left: 18px; }
.tl-item { position: relative; display: grid; grid-template-columns: 90px 1fr; gap: 14px; padding: 6px 0 14px; }
.tl-item::before { content: ''; position: absolute; left: -25px; top: 12px; width: 10px; height: 10px; border-radius: 50%; background: var(--green); }
.tl-ver { display: flex; flex-direction: column; align-items: flex-start; gap: 3px; }
.tl-item ul { margin: 0; padding-left: 18px; }
.tl-item li { margin: 2px 0; }

/* ---------- nav badge ---------- */
.nav-badge { display: inline-block; min-width: 18px; padding: 0 5px; margin-left: 3px; border-radius: 999px; background: var(--orange); color: #001e2b; font-size: .72rem; font-weight: 700; line-height: 18px; text-align: center; }
.nav-badge[hidden] { display: none; }

/* ---------- review, mock, exams ---------- */
.wrap > p.lead { font-size: 1.12rem; color: var(--muted); }
.srs-card .ans, .mock-card .ans, #mkBody .ans { margin-top: 12px; padding: 12px 16px; border-left: 3px solid var(--green); background: var(--panel2); border-radius: 8px; }
.srs-card .quiz-q { border: none; padding: 0; background: none; }
.mock-q { font-size: 1.2rem; line-height: 1.45; margin: 14px 0; }
.notes { width: 100%; min-height: 110px; margin: 6px 0 12px; resize: vertical; background: var(--panel2); color: var(--text); border: 1px solid var(--border); border-radius: 8px; padding: 10px 12px; font: inherit; font-size: .92rem; }
.grade-row { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; margin-top: 10px; }
.grade-row .btn { flex-direction: column; align-items: flex-start; gap: 2px; }
.grade-row .btn small { font-weight: 400; color: var(--muted); font-size: .76rem; }
.grade-again { border-left: 3px solid var(--red); }
.grade-hard { border-left: 3px solid var(--orange); }
.grade-good { border-left: 3px solid var(--blue); }
.grade-easy { border-left: 3px solid var(--green); }
.grade-pill-again, .grade-pill-skip { color: var(--red) !important; }
.grade-pill-hard { color: var(--orange) !important; }
.grade-pill-good { color: var(--blue) !important; }
.grade-pill-easy { color: var(--green) !important; }
.timer { font: 600 .95rem var(--mono); padding: 2px 10px; border-radius: 6px; background: var(--panel2); border: 1px solid var(--border); }
.timer.over { color: var(--red); border-color: var(--red); }
.exam-card { margin: 18px 0; }
.exam-card .stats { grid-template-columns: repeat(4, 1fr); }
details.obj summary { font-size: .95rem; }
.obj-lessons { margin-top: 8px; }
.px-head { position: sticky; top: 58px; z-index: 5; margin-bottom: 12px; }
.px-nav { display: flex; flex-wrap: wrap; gap: 4px; margin-top: 10px; }
.px-nav button { width: 32px; height: 28px; border-radius: 6px; border: 1px solid var(--border); background: var(--panel2); color: var(--muted); font-size: .78rem; cursor: pointer; }
.px-nav button.done { background: color-mix(in srgb, var(--green) 18%, var(--panel2)); color: var(--text); }
.px-nav button.flag { border-color: var(--orange); box-shadow: inset 0 -3px 0 var(--orange); }
.px-nav button.cur { outline: 2px solid var(--green); }

/* ---------- scenarios ---------- */
.sc-card .sc-alert { color: var(--muted); font-size: .92rem; border-left: 3px solid var(--red); padding-left: 10px; margin: 10px 0; }
.sc-layout { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.1fr); gap: 24px; margin-top: 16px; align-items: start; }
.sc-console { position: sticky; top: 70px; display: flex; flex-direction: column; gap: 10px; }
.sc-console #scOut { max-height: 52vh; overflow: auto; border-radius: var(--radius); }
.checklist { list-style: none; padding: 0; margin: 6px 0 0; }
.checklist li { display: flex; gap: 8px; align-items: baseline; padding: 5px 0; border-bottom: 1px dashed var(--border); }
.checklist .mark { font-weight: 700; width: 16px; }
.checklist li.ok .mark { color: var(--green); }
.checklist li.no .mark { color: var(--red); }

@media (max-width: 1100px) {
  .sc-layout { grid-template-columns: 1fr; }
  .sc-console { position: static; }
}
@media (max-width: 860px) {
  .grade-row, .exam-card .stats { grid-template-columns: 1fr 1fr; }
  .tl-item { grid-template-columns: 1fr; }
}

/* ---------- responsive guards ---------- */
/* A plain 1fr track never shrinks below its content, so one long code line or table would widen the whole page on a phone. */
.g2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.g3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.g4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
:not(pre) > code { overflow-wrap: anywhere; }
/* anywhere also shrinks a table column's minimum width, which splits short names like "inventory" mid-word. */
td > code { overflow-wrap: break-word; }
pre { max-width: 100%; overflow-x: auto; }
@media (max-width: 1100px) {
  .g4 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .hero, .ex-layout, .sc-layout { grid-template-columns: minmax(0, 1fr); }
}
@media (max-width: 860px) {
  .lesson-layout, .pg { grid-template-columns: minmax(0, 1fr); }
  .g2, .g3, .stats { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  table.tbl, .sec table, .ans table, .callout table { display: block; max-width: 100%; overflow-x: auto; }
  .ex-row { flex-wrap: wrap; }
}
@media (max-width: 600px) {
  .g2, .g3 { grid-template-columns: minmax(0, 1fr); }
  .topbar { gap: 8px; padding: 10px 12px; }
  .top-actions { gap: 6px; }
  #searchBtn kbd { display: none; }
}
@media (max-width: 760px) {
  #themeBtn { display: none; }
}
@media (max-width: 480px) {
  #searchBtn { display: none; }
  .brand { font-size: .95rem; gap: 7px; }
  .top-actions .icon-btn { white-space: nowrap; }
}

/* ---------- grouped nav, focus, hero ---------- */
.nav { align-items: center; }
.nav-menu { position: relative; }
.nav-menu-btn { font: inherit; font-size: .92rem; font-weight: 500; color: var(--muted); background: none; border: 0; padding: 6px 11px; border-radius: 8px; cursor: pointer; display: inline-flex; align-items: center; gap: 7px; }
.nav-menu-btn::after { content: ''; width: 5px; height: 5px; border-right: 1.5px solid currentColor; border-bottom: 1.5px solid currentColor; transform: translateY(-2px) rotate(45deg); opacity: .7; }
.nav-menu-btn:hover, .nav-menu.open > .nav-menu-btn { color: var(--text); background: var(--panel); }
.nav-menu.active > .nav-menu-btn { color: var(--green); background: color-mix(in srgb, var(--green) 10%, transparent); }
.nav-pop { display: none; position: absolute; top: calc(100% + 6px); left: 0; z-index: 60; min-width: 210px; flex-direction: column; gap: 2px; padding: 6px; background: var(--panel); border: 1px solid var(--border); border-radius: 10px; box-shadow: var(--shadow); }
.nav-menu.open > .nav-pop { display: flex; }
.nav-pop a { white-space: nowrap; }
a:focus-visible, button:focus-visible, summary:focus-visible { outline: 2px solid var(--green); outline-offset: 2px; }
:focus:not(:focus-visible) { outline: none; }
.hero { grid-template-columns: minmax(0, 1.1fr) minmax(0, .9fr); }
.hero-term pre { font-size: clamp(.7rem, .78vw, .82rem); overflow-x: auto; }
@media (max-width: 1240px) {
  #searchBtn kbd { display: none; }
}
@media (max-width: 1100px) {
  .hero { grid-template-columns: minmax(0, 1fr); }
}
@media (max-width: 860px) {
  .nav.open .nav-menu-btn { pointer-events: none; padding: 12px 11px 4px; font-size: .72rem; letter-spacing: .08em; text-transform: uppercase; color: var(--faint); background: none; }
  .nav.open .nav-menu-btn::after { display: none; }
  .nav.open .nav-pop { display: flex; position: static; min-width: 0; padding: 0 0 0 8px; border: 0; box-shadow: none; background: none; }
}

/* ---------- resume ---------- */
.resume { display: flex; flex-wrap: wrap; align-items: center; gap: 16px 28px; margin: 22px 0 6px; padding: 18px 20px; background: var(--panel); border: 1px solid var(--border); border-left: 3px solid var(--green); border-radius: var(--radius); }
.resume-main { flex: 1 1 360px; min-width: 0; }
.resume-main h2 { margin: 4px 0 4px; font-size: 1.3rem; }
.resume-main .progressbar > i { background: var(--green); }
.resume-side { display: flex; flex-wrap: wrap; gap: 8px; }

/* ---------- build projects ---------- */
.pr-step { margin: 14px 0; }
.pr-step .code { margin: 10px 0; }
.pr-out:not(:empty) { margin-top: 10px; max-height: 480px; overflow: auto; border-radius: 8px; }

/* ---------- interactive labs ---------- */
.sim-grid { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: 8px 16px; margin: 14px 0; }
.sim-list { display: grid; gap: 8px; margin: 14px 0; }
.sim-head { font-weight: 700; color: var(--muted); font-size: .8rem; letter-spacing: .06em; text-transform: uppercase; padding-bottom: 4px; border-bottom: 1px solid var(--border); }
.sim-step { border: 1px solid var(--border); border-left: 3px solid var(--blue); border-radius: 8px; background: var(--panel); padding: 8px 10px; min-width: 0; }
.sim-step.err { border-left-color: var(--red); }
.sim-step.err .sim-out { color: var(--red); }
.sim-step.cur { box-shadow: 0 0 0 2px color-mix(in srgb, var(--green) 55%, transparent); }
.sim-step pre { margin: 0; padding: 0; background: none; border: 0; white-space: pre-wrap; word-break: break-word; font: .8rem/1.5 var(--mono); }
.sim-sql { color: var(--text); }
.sim-out { color: var(--muted); margin-top: 4px !important; max-height: 220px; overflow: auto; }
.sim-next { grid-column: 1; color: var(--faint); font-size: .8rem; border: 1px dashed var(--border); border-radius: 8px; padding: 6px 10px; }
.sim-next.b { grid-column: 2; }
.sim-list .sim-next { grid-column: auto; }
.sim-note { min-height: 58px; }
.shards.lab { grid-template-columns: repeat(var(--cols, 3), minmax(0, 1fr)); }
@media (max-width: 860px) { .sim-grid { gap: 6px 8px; } .sim-step pre { font-size: .72rem; } .shards.lab { grid-template-columns: repeat(2, minmax(0, 1fr)); } }

/* Accessibility: links inside running text need more than colour to stand out (WCAG 1.4.1),
   and code that scrolls sideways must be reachable by keyboard. */
:where(p, li, td, footer, .crumbs, .callout, .ans) a:not(.btn):not(.pill):not(.ver-pill):not(.card) { text-decoration: underline; text-decoration-thickness: 1px; text-underline-offset: 2px; }
pre[tabindex]:focus-visible { outline: 2px solid var(--green); outline-offset: 2px; }