:root {
  --bg: #f6f7fb;
  --surface: #ffffff;
  --surface-2: #eef1f7;
  --border: #dde2ec;
  --text: #1b2230;
  --muted: #5d6879;
  --accent: #2f6fed;
  --accent-soft: #e3ecff;
  --ok: #1f9d63;
  --ok-soft: #dcf4e8;
  --warn: #c7811a;
  --warn-soft: #fcf0dc;
  --bad: #d64545;
  --bad-soft: #fbe3e3;
  --p1: #2f6fed;
  --p2: #9b51e0;
  --p3: #e0761b;
  --shadow: 0 1px 2px rgba(20, 30, 50, .06), 0 4px 14px rgba(20, 30, 50, .05);
  --radius: 12px;
  --sidebar: 264px;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0f131a; --surface: #171c25; --surface-2: #1f2632; --border: #2c3543;
    --text: #e6eaf2; --muted: #9aa5b7; --accent: #6b9bff; --accent-soft: #1d2a45;
    --ok: #43c68a; --ok-soft: #173228; --warn: #e6a84a; --warn-soft: #3a2d17;
    --bad: #f07a7a; --bad-soft: #3b1f22; --p1: #6b9bff; --p2: #bb86fc; --p3: #f5a25a;
    --shadow: 0 1px 2px rgba(0,0,0,.4); color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #0f131a; --surface: #171c25; --surface-2: #1f2632; --border: #2c3543;
  --text: #e6eaf2; --muted: #9aa5b7; --accent: #6b9bff; --accent-soft: #1d2a45;
  --ok: #43c68a; --ok-soft: #173228; --warn: #e6a84a; --warn-soft: #3a2d17;
  --bad: #f07a7a; --bad-soft: #3b1f22; --p1: #6b9bff; --p2: #bb86fc; --p3: #f5a25a;
  --shadow: 0 1px 2px rgba(0,0,0,.4); color-scheme: dark;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 76px; }
body {
  margin: 0; background: var(--bg); color: var(--text);
  font-family: "Inter", system-ui, -apple-system, "Segoe UI", sans-serif;
  font-size: 16px; line-height: 1.6; -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
code, .mono { font-family: "JetBrains Mono", ui-monospace, Consolas, monospace; font-size: .9em; }
h1, h2, h3, h4 { line-height: 1.25; margin: 1.6em 0 .6em; }
h1 { font-size: clamp(1.6rem, 4vw, 2.2rem); margin-top: .2em; }
h2 { font-size: 1.45rem; padding-bottom: .3em; border-bottom: 1px solid var(--border); }
h3 { font-size: 1.15rem; }
h2 i, h3 i { color: var(--accent); margin-right: .4em; }
p { margin: .6em 0; }
ul, ol { padding-left: 1.3em; }
li { margin: .25em 0; }
hr { border: 0; border-top: 1px solid var(--border); margin: 2em 0; }

/* ---------- Layout ---------- */
.topbar {
  position: sticky; top: 0; z-index: 50; height: 60px;
  display: flex; align-items: center; gap: 12px; padding: 0 16px;
  background: color-mix(in srgb, var(--surface) 88%, transparent);
  backdrop-filter: blur(8px); border-bottom: 1px solid var(--border);
}
.brand { display: flex; align-items: center; gap: 10px; font-weight: 700; color: var(--text); white-space: nowrap; }
.brand:hover { text-decoration: none; }
.brand .logo {
  width: 34px; height: 34px; border-radius: 9px; display: grid; place-items: center;
  background: var(--accent); color: #fff; font-size: 1rem;
}
.topbar .spacer { flex: 1; }
.icon-btn {
  width: 40px; height: 40px; border-radius: 10px; border: 1px solid var(--border);
  background: var(--surface); color: var(--text); cursor: pointer; display: grid; place-items: center; font-size: 1rem;
}
.icon-btn:hover { background: var(--surface-2); }
#menuBtn { display: none; }
.search { position: relative; width: min(340px, 40vw); }
.search input {
  width: 100%; height: 40px; border-radius: 10px; border: 1px solid var(--border);
  background: var(--surface-2); color: var(--text); padding: 0 12px 0 36px; font: inherit; font-size: .95rem;
}
.search > i { position: absolute; left: 12px; top: 12px; color: var(--muted); }
.search-results {
  position: absolute; top: 46px; right: 0; left: 0; min-width: 280px; max-height: 60vh; overflow: auto;
  background: var(--surface); border: 1px solid var(--border); border-radius: 10px; box-shadow: var(--shadow); display: none;
}
.search-results.open { display: block; }
.search-results a { display: block; padding: 8px 12px; color: var(--text); border-bottom: 1px solid var(--border); font-size: .92rem; }
.search-results a small { display: block; color: var(--muted); }
.search-results a:hover { background: var(--surface-2); text-decoration: none; }

.layout { display: flex; min-height: calc(100vh - 60px); }
.sidebar {
  width: var(--sidebar); flex-shrink: 0; position: sticky; top: 60px; height: calc(100vh - 60px);
  overflow-y: auto; padding: 16px 12px 40px; border-right: 1px solid var(--border); background: var(--surface);
}
.sidebar .group { font-size: .72rem; text-transform: uppercase; letter-spacing: .08em; color: var(--muted); margin: 18px 10px 6px; font-weight: 600; }
.sidebar a {
  display: flex; align-items: center; gap: 10px; padding: 8px 10px; border-radius: 8px; color: var(--text); font-size: .95rem;
}
.sidebar a i { width: 18px; text-align: center; color: var(--muted); }
.sidebar a:hover { background: var(--surface-2); text-decoration: none; }
.sidebar a.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.sidebar a.active i { color: var(--accent); }
.sidebar .toc { margin: 2px 0 8px 28px; border-left: 2px solid var(--border); }
.sidebar .toc a { font-size: .85rem; padding: 4px 10px; color: var(--muted); border-radius: 0 6px 6px 0; }

main { flex: 1; min-width: 0; padding: 28px clamp(16px, 4vw, 48px) 80px; }
.content { max-width: 920px; margin: 0 auto; }
.backdrop { display: none; }

@media (max-width: 900px) {
  #menuBtn { display: grid; }
  .sidebar {
    position: fixed; left: 0; top: 60px; z-index: 40; transform: translateX(-100%); transition: transform .2s ease;
    box-shadow: var(--shadow);
  }
  body.nav-open .sidebar { transform: none; }
  body.nav-open .backdrop { display: block; position: fixed; inset: 60px 0 0; background: rgba(0,0,0,.35); z-index: 30; }
  .brand span.long { display: none; }
  .search { width: auto; flex: 1; min-width: 0; }
  .topbar .spacer { display: none; }
}

/* ---------- Components ---------- */
.lead { font-size: 1.1rem; color: var(--muted); }
.card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 18px 20px; box-shadow: var(--shadow); margin: 16px 0;
}
.card > h3:first-child, .card > h4:first-child { margin-top: 0; }
.grid { display: grid; gap: 14px; grid-template-columns: repeat(auto-fit, minmax(230px, 1fr)); }
.grid-2 { display: grid; gap: 14px; grid-template-columns: repeat(auto-fit, minmax(320px, 1fr)); }
.grid .card, .grid-2 .card { margin: 0; }
a.card { display: block; color: var(--text); transition: transform .12s, border-color .12s; }
a.card:hover { text-decoration: none; border-color: var(--accent); transform: translateY(-2px); }
.card .big-icon {
  width: 44px; height: 44px; border-radius: 11px; display: grid; place-items: center; font-size: 1.2rem;
  background: var(--accent-soft); color: var(--accent); margin-bottom: 10px;
}
.card .big-icon.p2 { background: color-mix(in srgb, var(--p2) 16%, transparent); color: var(--p2); }
.card .big-icon.p3 { background: color-mix(in srgb, var(--p3) 16%, transparent); color: var(--p3); }
.card .big-icon.ok { background: var(--ok-soft); color: var(--ok); }
.card h4 { margin: 0 0 4px; font-size: 1.05rem; }
.card p.small, .small { font-size: .9rem; color: var(--muted); }

.hero {
  background: linear-gradient(135deg, var(--accent-soft), color-mix(in srgb, var(--p2) 14%, var(--surface)));
  border: 1px solid var(--border); border-radius: 16px; padding: clamp(20px, 4vw, 36px); margin-bottom: 24px;
}
.hero p { max-width: 640px; }

.badge {
  display: inline-flex; align-items: center; gap: 5px; font-size: .75rem; font-weight: 600; padding: 2px 9px;
  border-radius: 999px; background: var(--surface-2); color: var(--muted); border: 1px solid var(--border); white-space: nowrap;
}
.badge.p1 { color: var(--p1); background: color-mix(in srgb, var(--p1) 12%, transparent); border-color: transparent; }
.badge.p2 { color: var(--p2); background: color-mix(in srgb, var(--p2) 12%, transparent); border-color: transparent; }
.badge.p3 { color: var(--p3); background: color-mix(in srgb, var(--p3) 12%, transparent); border-color: transparent; }
.badge.ok { color: var(--ok); background: var(--ok-soft); border-color: transparent; }

.callout {
  border-left: 4px solid var(--accent); background: var(--accent-soft); padding: 12px 16px; border-radius: 0 10px 10px 0; margin: 16px 0;
}
.callout.warn { border-color: var(--warn); background: var(--warn-soft); }
.callout.ok { border-color: var(--ok); background: var(--ok-soft); }
.callout.bad { border-color: var(--bad); background: var(--bad-soft); }
.callout > strong:first-child { display: block; margin-bottom: 2px; }
.callout > strong:first-child i { margin-right: 6px; }

.formula {
  background: var(--surface-2); border: 1px solid var(--border); border-radius: 10px; padding: 10px 14px; margin: 12px 0; overflow-x: auto;
}
.katex-display { margin: .5em 0; overflow-x: auto; overflow-y: hidden; padding: 2px 0; position: relative; }
.formula, .table-wrap, .out, figure { position: relative; }
.katex { max-width: 100%; }
main { overflow-x: clip; }

table { border-collapse: collapse; width: 100%; font-size: .93rem; }
.table-wrap { overflow-x: auto; margin: 12px 0; border: 1px solid var(--border); border-radius: 10px; }
th, td { padding: 9px 12px; border-bottom: 1px solid var(--border); text-align: left; vertical-align: top; }
th { background: var(--surface-2); font-weight: 600; }
tr:last-child td { border-bottom: 0; }

.steps { counter-reset: step; list-style: none; padding-left: 0; }
.steps > li { counter-increment: step; position: relative; padding: 4px 0 12px 48px; margin: 0; }
.steps > li::before {
  content: counter(step); position: absolute; left: 0; top: 2px; width: 32px; height: 32px; border-radius: 50%;
  background: var(--accent); color: #fff; font-weight: 700; display: grid; place-items: center; font-size: .9rem;
}
.steps > li:not(:last-child)::after {
  content: ""; position: absolute; left: 15px; top: 38px; bottom: 0; width: 2px; background: var(--border);
}

details {
  background: var(--surface); border: 1px solid var(--border); border-radius: 10px; margin: 10px 0; overflow: hidden;
}
details > summary {
  cursor: pointer; padding: 12px 16px; font-weight: 600; list-style: none; display: flex; align-items: center; gap: 10px;
}
details > summary::-webkit-details-marker { display: none; }
details > summary::before { content: "\f054"; font-family: "Font Awesome 6 Free"; font-weight: 900; font-size: .75rem; transition: transform .15s; color: var(--muted); }
details[open] > summary::before { transform: rotate(90deg); }
details > .body { padding: 0 16px 14px; border-top: 1px solid var(--border); }

/* Forms / tools */
label { font-size: .85rem; color: var(--muted); display: block; margin-bottom: 3px; font-weight: 500; }
input[type=number], input[type=text], select, textarea {
  width: 100%; padding: 8px 10px; border-radius: 8px; border: 1px solid var(--border); background: var(--surface);
  color: var(--text); font: inherit; font-size: .95rem; min-height: 40px;
}
input:focus, select:focus, textarea:focus { outline: 2px solid var(--accent); outline-offset: -1px; }
.form-grid { display: grid; gap: 12px; grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); margin: 10px 0; }
.btn {
  display: inline-flex; align-items: center; gap: 8px; padding: 9px 16px; border-radius: 9px; border: 1px solid var(--accent);
  background: var(--accent); color: #fff; font: inherit; font-weight: 600; font-size: .93rem; cursor: pointer; min-height: 40px;
}
.btn:hover { filter: brightness(1.08); text-decoration: none; }
.btn.ghost { background: transparent; color: var(--accent); }
.btn.subtle { background: var(--surface-2); color: var(--text); border-color: var(--border); }
.btn.danger { background: transparent; color: var(--bad); border-color: var(--bad); }
.btn-row { display: flex; flex-wrap: wrap; gap: 8px; margin: 12px 0; }
.out {
  background: var(--surface-2); border: 1px solid var(--border); border-radius: 10px; padding: 12px 16px; margin-top: 12px; overflow-x: auto;
}
.out:empty { display: none; }
.kv { display: grid; grid-template-columns: repeat(auto-fill, minmax(170px, 1fr)); gap: 8px; }
.kv div { background: var(--surface); border: 1px solid var(--border); border-radius: 8px; padding: 8px 10px; }
.kv div span { display: block; font-size: .78rem; color: var(--muted); }
.kv div b { font-family: "JetBrains Mono", monospace; font-size: .95rem; }
.err { color: var(--bad); font-weight: 600; }

.tabs { display: flex; gap: 6px; flex-wrap: wrap; margin: 10px 0 14px; }
.tabs button {
  border: 1px solid var(--border); background: var(--surface); color: var(--text); padding: 7px 14px; border-radius: 999px;
  font: inherit; font-size: .9rem; cursor: pointer;
}
.tabs button.active { background: var(--accent); color: #fff; border-color: var(--accent); }
.tab-panel { display: none; }
.tab-panel.active { display: block; }

canvas.plot { width: 100%; height: 260px; background: var(--surface); border: 1px solid var(--border); border-radius: 10px; display: block; margin-top: 12px; }
svg.circuit { max-width: 100%; height: auto; display: block; margin: 10px auto; color: var(--text); }
svg.circuit text { fill: currentColor; font-family: "Inter", sans-serif; font-size: 13px; }
figure { margin: 14px 0; text-align: center; }
figcaption { font-size: .85rem; color: var(--muted); }

.load-row { display: grid; grid-template-columns: 1fr auto; gap: 8px; align-items: end; padding: 12px; border: 1px dashed var(--border); border-radius: 10px; margin: 10px 0; }

/* Progress */
.progress { height: 10px; border-radius: 99px; background: var(--surface-2); overflow: hidden; border: 1px solid var(--border); }
.progress > div { height: 100%; background: var(--ok); width: 0; transition: width .3s; }
.check-list { list-style: none; padding: 0; }
.check-list li { display: flex; align-items: flex-start; gap: 10px; padding: 8px 4px; border-bottom: 1px solid var(--border); }
.check-list input { width: 18px; height: 18px; margin-top: 4px; accent-color: var(--ok); flex-shrink: 0; }
.check-list li.done label { text-decoration: line-through; color: var(--muted); }
.check-list label { font-size: .95rem; color: var(--text); margin: 0; cursor: pointer; }

/* Bars */
.bar-row { display: grid; grid-template-columns: minmax(120px, 190px) 1fr 52px; gap: 10px; align-items: center; margin: 8px 0; font-size: .92rem; }
.bar { height: 14px; background: var(--surface-2); border-radius: 99px; overflow: hidden; }
.bar > div { height: 100%; border-radius: 99px; background: var(--accent); }
.bar-row .v { text-align: right; font-family: "JetBrains Mono", monospace; font-size: .85rem; color: var(--muted); }

/* Quiz */
.flashcard {
  min-height: 220px; perspective: 1200px; cursor: pointer; margin: 14px 0;
}
.flashcard .inner { position: relative; min-height: 220px; transition: transform .45s; transform-style: preserve-3d; }
.flashcard.flipped .inner { transform: rotateY(180deg); }
.flashcard .face {
  position: absolute; inset: 0; backface-visibility: hidden; background: var(--surface); border: 1px solid var(--border);
  border-radius: 14px; padding: 22px; display: flex; flex-direction: column; justify-content: center; box-shadow: var(--shadow); overflow: auto;
}
.flashcard .back { transform: rotateY(180deg); background: var(--accent-soft); }
.flashcard .face small { color: var(--muted); text-transform: uppercase; letter-spacing: .06em; font-size: .72rem; margin-bottom: 8px; }
.opt {
  display: block; width: 100%; text-align: left; padding: 11px 14px; margin: 8px 0; border-radius: 10px; border: 1px solid var(--border);
  background: var(--surface); color: var(--text); font: inherit; cursor: pointer;
}
.opt:hover { border-color: var(--accent); }
.opt.right { background: var(--ok-soft); border-color: var(--ok); }
.opt.wrong { background: var(--bad-soft); border-color: var(--bad); }
.opt:disabled { cursor: default; }

.exam-item { display: flex; flex-direction: column; gap: 6px; }
.exam-item .tags { display: flex; flex-wrap: wrap; gap: 6px; }
.filters { display: flex; flex-wrap: wrap; gap: 8px; margin: 12px 0; }

.pager { display: flex; justify-content: space-between; gap: 12px; margin-top: 40px; flex-wrap: wrap; }
.pager a { flex: 1; min-width: 200px; padding: 14px 16px; border: 1px solid var(--border); border-radius: 10px; background: var(--surface); color: var(--text); }
.pager a small { display: block; color: var(--muted); }
.pager a.next { text-align: right; }
.pager a:hover { border-color: var(--accent); text-decoration: none; }

footer { text-align: center; color: var(--muted); font-size: .85rem; padding: 30px 16px; border-top: 1px solid var(--border); }

.to-top {
  position: fixed; right: 18px; bottom: 18px; width: 44px; height: 44px; border-radius: 50%; border: 0; background: var(--accent);
  color: #fff; cursor: pointer; box-shadow: var(--shadow); display: none; z-index: 20;
}
.to-top.show { display: grid; place-items: center; }

.solution { display: none; }
.solution.show { display: block; }

@media print {
  .topbar, .sidebar, .to-top, .pager, footer, .btn, .no-print { display: none !important; }
  main { padding: 0; }
  .card, details { box-shadow: none; break-inside: avoid; }
  details > .body { display: block !important; }
}

/* ---------- Esercizi guidati ---------- */
.gcards { display: grid; gap: 12px; grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); margin: 14px 0 26px; }
.gcard {
  display: flex; flex-direction: column; gap: 4px; text-align: left; cursor: pointer;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 14px 16px; color: var(--text); font: inherit; box-shadow: var(--shadow);
}
.gcard:hover { border-color: var(--accent); }
.gcard.active { border-color: var(--accent); background: var(--accent-soft); }
.gcard-top { display: flex; justify-content: space-between; gap: 8px; margin-bottom: 4px; flex-wrap: wrap; }
.gcard .small { color: var(--muted); }
.gstep { border-left: 3px solid var(--accent); }
.stepnum {
  width: 32px; height: 32px; flex-shrink: 0; border-radius: 50%; background: var(--accent); color: #fff;
  display: grid; place-items: center; font-weight: 700; font-size: .9rem;
}
.gq { font-weight: 600; margin-bottom: 10px; }
.gsol { margin-top: 12px; }
.gsol.warn { border-color: var(--warn); background: var(--warn-soft); }
.gbtns { margin: 10px 0 0; }
#exFinal .card, #exFinal.card { border: 2px solid var(--ok); }
.demo-step { border-left-color: var(--p2); background: color-mix(in srgb, var(--surface) 92%, var(--accent-soft)); }
.stepnum.demo { background: var(--p2); }
#exMode button { font-weight: 600; }
.gbody { flex: 1; min-width: 0; }
.gbody .katex-display { max-width: 100%; }