/* study.courseloop.app: shared style (static, no build step, no libraries).
   Look: learn-by-doing course site. White ground, heavy type, flat tactile buttons with a solid
   bottom edge, rounded cards, a learning path of round lesson nodes, green/red answer feedback.
   The simulators (app.js) read --ink --sub --line --panel --accent --bad --warn --vx --vy --vr --vc
   --land --water --water-deep from here: keep those names. */
:root {
  --bg: #ffffff;
  --bg-2: #f6f7f9;
  --panel: #ffffff;
  --ink: #16171a;
  --sub: #5f636b;
  --line: #e3e5e8;
  --edge: #d3d6db;
  --soft: #f1f2f4;
  --accent: #5b4bdb;
  --accent-ink: #ffffff;
  --accent-edge: #3f31b0;
  --accent-soft: #eeebff;
  --go: #2fb062;
  --go-edge: #1f8a49;
  --go-soft: #e4f7eb;
  --btn: #16171a;
  --btn-ink: #ffffff;
  --btn-edge: #000000;
  --water: #bfe2f7;
  --water-deep: #8cc7ea;
  --land: #c9dcae;
  --vx: #0f8a5f;
  --vy: #d4520f;
  --vr: #5b4bdb;
  --vc: #0b78b8;
  --warn: #b45309;
  --warn-soft: #fff4e0;
  --ok: #1f8a49;
  --ok-soft: #e4f7eb;
  --bad: #c62828;
  --bad-soft: #fdeaea;
  --c-phys: #ffb547;
  --c-phys-2: #ffd88f;
  /* one colour per kind of lesson (course.js sets data-k) */
  --k-teoria: #5b4bdb;    --k-teoria-soft: #eeebff;
  --k-simulador: #e8771a; --k-simulador-soft: #fff0e0;
  --k-exercicis: #1f9d55; --k-exercicis-soft: #e2f6ea;
  --k-practica: #d63f86;  --k-practica-soft: #fde7f1;
  --k-resum: #0b78b8;     --k-resum-soft: #e1f0fa;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --sans: "Inter", ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --r: 16px;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #111215;
    --bg-2: #17181c;
    --panel: #1b1c21;
    --ink: #f1f2f4;
    --sub: #a4a8b1;
    --line: #2e3037;
    --edge: #3a3d45;
    --soft: #23252b;
    --accent: #9d92ff;
    --accent-ink: #111215;
    --accent-edge: #6f62e0;
    --accent-soft: #2a2650;
    --go: #3cc474;
    --go-edge: #22894c;
    --go-soft: #173826;
    --btn: #f1f2f4;
    --btn-ink: #111215;
    --btn-edge: #9da1aa;
    --water: #173d55;
    --water-deep: #1f5170;
    --land: #2f3d26;
    --vx: #34d399;
    --vy: #fb923c;
    --vr: #a59bff;
    --vc: #38bdf8;
    --warn: #fbbf24;
    --warn-soft: #3a2c10;
    --ok: #4ade80;
    --ok-soft: #173826;
    --bad: #f87171;
    --bad-soft: #3d1a1a;
    --c-phys: #c9862a;
    --c-phys-2: #7a5220;
    --k-teoria: #9d92ff;    --k-teoria-soft: #2a2650;
    --k-simulador: #ffa04d; --k-simulador-soft: #3a2611;
    --k-exercicis: #3cc474; --k-exercicis-soft: #173826;
    --k-practica: #ff7ab6;  --k-practica-soft: #3d1a2b;
    --k-resum: #4cb8f5;     --k-resum-soft: #13304a;
    color-scheme: dark;
  }
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 80px; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font: 17px/1.6 var(--sans);
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); }
h1, h2, h3, h4 { line-height: 1.15; margin: 0 0 .5em; letter-spacing: -.015em; font-weight: 800; }
h2 { font-size: clamp(1.6rem, 3.4vw, 2.2rem); margin-top: .1em; }
h3 { font-size: 1.2rem; }
p { margin: 0 0 .8em; }
code, .m { font-family: var(--mono); font-size: .93em; }
.m { white-space: nowrap; }
.step .m, .explain .m, .tf-card .m { white-space: normal; }
@media (max-width: 560px) { p .m, li .m { white-space: normal; } }
sub, sup { font-size: .72em; }
[hidden] { display: none !important; }

/* ---------- top bar ---------- */
.top {
  position: sticky; top: 0; z-index: 20;
  background: color-mix(in srgb, var(--bg) 94%, transparent);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--line);
}
.top-in {
  max-width: 1180px; margin: 0 auto; padding: 10px 16px; min-height: 60px;
  display: flex; align-items: center; gap: 14px;
}
.logo { display: inline-flex; align-items: center; gap: 10px; font-weight: 800; font-size: 1.1rem;
  color: var(--ink); text-decoration: none; letter-spacing: -.02em; white-space: nowrap; }
.logo-mark { width: 30px; height: 30px; border-radius: 9px; background: var(--ink); color: var(--bg);
  display: grid; place-items: center; font-size: .95rem; }
.logo small { font-weight: 600; color: var(--sub); font-size: .95rem; }
.top .spacer { flex: 1; }
.brand { font-weight: 800; white-space: nowrap; text-decoration: none; color: var(--ink); }
.brand.back { color: var(--sub); font-weight: 700; font-size: .95rem; padding: 6px 12px 6px 8px; border-radius: 999px; }
.brand.back:hover { color: var(--ink); background: var(--soft); }
.top-title { font-weight: 800; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; min-width: 0; }
.top-progress { display: flex; align-items: center; gap: 10px; font-size: .88rem; color: var(--sub); font-weight: 700; white-space: nowrap; }
.top-progress .bar { width: 120px; }
@media (max-width: 640px) { .top-progress .bar { width: 64px; } .logo small { display: none; } }

/* progress bar */
.bar { height: 10px; border-radius: 999px; background: var(--soft); overflow: hidden; }
.bar > i { display: block; height: 100%; width: 0; border-radius: inherit; background: var(--go); transition: width .4s ease; }

/* ---------- buttons, inputs ---------- */
button, .btn {
  font: inherit; font-weight: 700; font-size: .95rem; cursor: pointer; text-decoration: none;
  display: inline-block; text-align: center; vertical-align: middle; line-height: 1.4;
  color: var(--ink); background: var(--panel);
  border: 2px solid var(--edge); border-radius: 12px;
  padding: 7px 16px; box-shadow: 0 3px 0 var(--edge);
  transition: transform .06s ease, box-shadow .06s ease, background .15s ease;
}
button:hover, .btn:hover { background: var(--bg-2); }
button:active, .btn:active { transform: translateY(2px); box-shadow: 0 1px 0 var(--edge); }
button:disabled { cursor: default; opacity: .55; transform: none; box-shadow: 0 3px 0 var(--edge); }
button:focus-visible, .btn:focus-visible, a:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
button.primary, .btn.primary { background: var(--btn); color: var(--btn-ink); border-color: var(--btn); box-shadow: 0 3px 0 var(--btn-edge); }
button.primary:hover, .btn.primary:hover { background: color-mix(in srgb, var(--btn) 88%, var(--bg)); }
button.primary:active, .btn.primary:active { box-shadow: 0 1px 0 var(--btn-edge); }
.btn.go, button.go { background: var(--go); color: #fff; border-color: var(--go); box-shadow: 0 4px 0 var(--go-edge); }
.btn.go:hover, button.go:hover { background: color-mix(in srgb, var(--go) 90%, #000); }
.btn.go:active, button.go:active { box-shadow: 0 1px 0 var(--go-edge); }
.btn.big, button.big { font-size: 1.05rem; padding: 12px 26px; border-radius: 14px; }
button.on { background: var(--accent-soft); border-color: var(--accent); box-shadow: 0 3px 0 var(--accent-edge); color: var(--ink); }
.btnrow { display: flex; flex-wrap: wrap; gap: 10px; margin: 10px 0; }
input[type="number"], input[type="text"] {
  font: inherit; font-weight: 600; width: 7.5em; padding: 7px 10px; border-radius: 10px;
  border: 2px solid var(--edge); background: var(--panel); color: var(--ink);
}
input[type="number"]:focus, input[type="text"]:focus { outline: none; border-color: var(--accent); }
input[type="range"] { width: 100%; accent-color: var(--accent); }
input[type="checkbox"] { accent-color: var(--accent); width: 16px; height: 16px; vertical-align: -2px; }
select { font: inherit; font-weight: 600; padding: 5px 10px; border-radius: 10px; border: 2px solid var(--edge); background: var(--panel); color: var(--ink); }

main { max-width: 1180px; margin: 0 auto; padding: 0 16px 80px; }
.kicker { color: var(--sub); font-weight: 800; letter-spacing: .06em; text-transform: uppercase; font-size: .78rem; margin-bottom: 6px; }
.lead { font-size: 1.12rem; color: var(--sub); max-width: 68ch; }

/* ======================================================================
   Home (study/index.html)
   ====================================================================== */
.home-hero { display: grid; grid-template-columns: 1.1fr .9fr; gap: 40px; align-items: center; padding: 64px 0 40px; }
.home-hero h1 { font-size: clamp(2.4rem, 6vw, 4rem); line-height: 1.02; letter-spacing: -.035em; margin-bottom: .35em; }
.home-hero h1 em { font-style: normal; color: var(--accent); }
.home-hero .lead { font-size: 1.2rem; }
.home-hero .btnrow { margin-top: 22px; }
.hero-art { width: 100%; height: auto; display: block; }
@media (max-width: 820px) { .home-hero { grid-template-columns: 1fr; padding-top: 36px; gap: 8px; } .hero-art { max-width: 420px; margin: 0 auto; } }

.feature-row { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; margin: 8px 0 56px; }
.feature { background: var(--bg-2); border-radius: var(--r); padding: 20px; }
.feature b { display: block; font-size: 1.05rem; margin-bottom: 4px; }
.feature span { color: var(--sub); font-size: .95rem; }
.feature .ico { width: 40px; height: 40px; border-radius: 12px; display: grid; place-items: center; margin-bottom: 12px; font-size: 1.2rem; background: var(--panel); border: 2px solid var(--line); }
@media (max-width: 820px) { .feature-row { grid-template-columns: 1fr; } }

.resume {
  display: flex; align-items: center; gap: 18px; flex-wrap: wrap;
  border: 2px solid var(--line); border-radius: 20px; padding: 18px 20px; margin: 0 0 48px;
  box-shadow: 0 4px 0 var(--line); background: var(--panel); color: var(--ink); text-decoration: none;
}
.resume:hover { border-color: var(--edge); box-shadow: 0 4px 0 var(--edge); }
.resume .resume-art { width: 64px; height: 64px; border-radius: 16px; background: var(--c-phys); display: grid; place-items: center; flex: none; }
.resume .resume-txt { flex: 1; min-width: 200px; }
.resume .resume-txt b { display: block; font-size: 1.15rem; }
.resume .resume-txt > span:first-child { display: block; }
.resume .resume-txt span { color: var(--sub); font-size: .92rem; }
.resume .bar { display: block; margin-top: 8px; max-width: 340px; }

.section-head { display: flex; align-items: end; justify-content: space-between; gap: 16px; flex-wrap: wrap; margin-bottom: 8px; }
.section-head h2 { margin: 0; }
.filters { display: flex; flex-wrap: wrap; gap: 8px; margin: 12px 0 4px; }
.filters button { border-radius: 999px; padding: 5px 14px; font-size: .88rem; }

.topics { display: grid; grid-template-columns: repeat(auto-fill, minmax(270px, 1fr)); gap: 20px; margin: 16px 0 56px; }
.topic {
  display: flex; flex-direction: column; text-decoration: none; color: var(--ink);
  background: var(--panel); border: 2px solid var(--line); border-radius: 20px; overflow: hidden;
  box-shadow: 0 4px 0 var(--line); transition: transform .12s ease, box-shadow .12s ease, border-color .12s ease;
}
.topic:hover { transform: translateY(-3px); border-color: var(--edge); box-shadow: 0 7px 0 var(--edge); }
.topic:active { transform: translateY(1px); box-shadow: 0 2px 0 var(--edge); }
.topic .topic-art { aspect-ratio: 16 / 9; background: var(--c-phys); display: block; }
.topic .topic-art svg { width: 100%; height: 100%; display: block; }
.topic .topic-body { padding: 16px 18px 18px; display: flex; flex-direction: column; gap: 8px; flex: 1; }
.topic .tag { align-self: flex-start; }
.topic h2 { font-size: 1.3rem; margin: 0; }
.topic p { margin: 0; color: var(--sub); font-size: .95rem; }
.topic .meta { display: flex; gap: 14px; color: var(--sub); font-size: .85rem; font-weight: 700; margin-top: auto; padding-top: 6px; }
.topic .topic-prog { display: flex; align-items: center; gap: 10px; font-size: .82rem; color: var(--sub); font-weight: 700; }
.topic .topic-prog .bar { flex: 1; height: 8px; }
.topic[hidden] { display: none; }
.topic.soon { pointer-events: none; opacity: .6; box-shadow: none; border-style: dashed; }

footer { max-width: 1180px; margin: 0 auto; padding: 24px 16px 48px; color: var(--sub); font-size: .88rem; border-top: 1px solid var(--line); }
.version { font-family: var(--mono); font-size: .8rem; }

/* ======================================================================
   Course page (a topic): overview with a learning path, then one lesson at a time
   ====================================================================== */
.course-hero { display: grid; grid-template-columns: 1fr 340px; gap: 40px; align-items: start; padding: 48px 0 24px; }
.course-hero h1 { font-size: clamp(2.1rem, 5vw, 3.3rem); letter-spacing: -.03em; line-height: 1.05; }
.course-card {
  border: 2px solid var(--line); border-radius: 20px; overflow: hidden; box-shadow: 0 4px 0 var(--line);
  position: sticky; top: 84px; background: var(--panel);
}
.course-card .topic-art { aspect-ratio: 16 / 10; background: var(--c-phys); }
.course-card .topic-art svg { width: 100%; height: 100%; display: block; }
.course-card .cc-body { padding: 16px 18px 20px; display: flex; flex-direction: column; gap: 12px; }
.course-card .cc-stat { display: flex; justify-content: space-between; font-size: .9rem; font-weight: 700; color: var(--sub); }
.course-card .btn { width: 100%; }
@media (max-width: 900px) { .course-hero { grid-template-columns: 1fr; gap: 20px; } .course-card { position: static; order: -1; } }

/* the learning path: round nodes that zigzag down a line */
.path { list-style: none; margin: 24px 0 0; padding: 0; position: relative; max-width: 560px; }
.path li { position: relative; display: flex; align-items: center; gap: 18px; padding: 10px 0; }
.path li:nth-child(4n+2) { padding-left: 56px; }
.path li:nth-child(4n+3) { padding-left: 96px; }
.path li:nth-child(4n+4) { padding-left: 56px; }
@media (max-width: 520px) { .path li:nth-child(n) { padding-left: 0; } }
.path a { display: flex; align-items: center; gap: 16px; text-decoration: none; color: var(--ink); min-width: 0; }
.node {
  width: 72px; height: 72px; flex: none; border-radius: 50%;
  display: grid; place-items: center; font-size: 1.6rem;
  background: var(--panel); border: 3px solid var(--edge); box-shadow: 0 5px 0 var(--edge);
  transition: transform .08s ease, box-shadow .08s ease;
}
.path a:hover .node { transform: translateY(-2px); box-shadow: 0 7px 0 var(--edge); }
.path a:active .node { transform: translateY(3px); box-shadow: 0 2px 0 var(--edge); }
.path .node svg { width: 34px; height: 34px; }
.path li.done .node { font-weight: 900; font-size: 1.9rem;
  background: var(--go); border-color: var(--go); box-shadow: 0 5px 0 var(--go-edge); color: #fff; }
.path li.next .node { background: var(--accent); border-color: var(--accent); box-shadow: 0 5px 0 var(--accent-edge); color: var(--accent-ink);
  animation: pulse 2.2s ease-in-out infinite; }
@keyframes pulse { 0%, 100% { outline: 0 solid transparent; } 50% { outline: 8px solid var(--accent-soft); } }
.path .lbl b { display: block; font-size: 1.05rem; line-height: 1.25; }
.path .lbl span { color: var(--sub); font-size: .85rem; font-weight: 700; }
.path li.next .lbl b::after { content: "  ← continua aquí"; color: var(--accent); font-size: .82rem; font-weight: 800; white-space: nowrap; }

/* lesson view: a slim path on the side + the lesson */
.course { display: grid; grid-template-columns: 250px minmax(0, 1fr); gap: 36px; align-items: start; }
.course.overview { display: block; }
.course.overview .side { display: none; }
.side { position: sticky; top: 84px; padding-top: 36px; }
.side ol { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: 2px; }
.side a { display: flex; align-items: center; gap: 10px; padding: 7px 10px; border-radius: 12px; text-decoration: none; color: var(--sub); font-weight: 700; font-size: .92rem; line-height: 1.25; }
.side a:hover { background: var(--soft); color: var(--ink); }
.side .dot { width: 26px; height: 26px; flex: none; border-radius: 50%; border: 2px solid var(--edge); display: grid; place-items: center; font-size: .75rem; color: var(--sub); background: var(--panel); }
.side li.done .dot { background: var(--go); border-color: var(--go); color: #fff; }
.side li.cur a { background: var(--accent-soft); color: var(--ink); }
.side li.cur .dot { border-color: var(--accent); color: var(--accent); }
.side .side-back { margin-bottom: 14px; font-size: .9rem; }
@media (max-width: 980px) { .course { grid-template-columns: minmax(0, 1fr); gap: 0; } .side { display: none; } }
.lessons { min-width: 0; }

.lesson-bar { display: flex; gap: 6px; margin: 28px 0 0; }
.lesson-bar a { flex: 1; height: 8px; border-radius: 999px; background: var(--soft); }
.lesson-bar a.done { background: var(--go); }
.lesson-bar a.cur { background: var(--accent); }
.course.overview .lesson-bar { display: none; }

section.block { padding: 28px 0 8px; }
.lesson-end {
  margin: 40px 0 0; padding: 24px; border-radius: 20px; background: var(--bg-2);
  display: flex; align-items: center; justify-content: space-between; gap: 16px; flex-wrap: wrap;
}
.lesson-end b { font-size: 1.15rem; display: block; }
.lesson-end span { color: var(--sub); font-size: .92rem; }
.lesson-end .btnrow { margin: 0; }

/* ======================================================================
   Lesson content (theory, simulators, exercises). Class names are shared with app.js.
   ====================================================================== */
.card { background: var(--panel); border: 2px solid var(--line); border-radius: var(--r); padding: 22px; margin: 18px 0; }
.grid2 { display: grid; grid-template-columns: 1fr 1fr; gap: 18px; }
.grid3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
.grid2 > .card, .grid3 > .card { margin: 0; }
.grid2, .grid3 { margin: 18px 0; }
.grid2 > *, .grid3 > *, .sim > *, .tf > * { min-width: 0; }
@media (max-width: 820px) { .grid2, .grid3 { grid-template-columns: 1fr; } }
.note { background: var(--accent-soft); border-radius: 14px; padding: 14px 18px; margin: 14px 0; }
.warnbox { background: var(--warn-soft); border-radius: 14px; padding: 14px 18px; margin: 14px 0; }
.formula {
  font-family: var(--mono); background: var(--bg-2); border: 2px solid var(--line); border-radius: 12px;
  padding: 10px 14px; margin: 8px 0; overflow-x: auto; white-space: nowrap;
}
.formula.big { font-size: 1.1rem; text-align: center; padding: 14px; }
table.eq { width: 100%; border-collapse: separate; border-spacing: 0; font-size: .95rem; border: 2px solid var(--line); border-radius: 12px; overflow: hidden; }
table.eq th, table.eq td { border-bottom: 1px solid var(--line); border-right: 1px solid var(--line); padding: 9px 12px; text-align: left; vertical-align: top; }
table.eq tr:last-child > * { border-bottom: 0; }
table.eq tr > *:last-child { border-right: 0; }
table.eq th { background: var(--bg-2); }
.tablewrap { overflow-x: auto; }
ol.steps-list { padding-left: 1.2em; }
ol.steps-list li { margin-bottom: .5em; }

details { border: 2px solid var(--line); border-radius: 14px; padding: 0 16px; margin: 10px 0; background: var(--panel); }
details > summary { cursor: pointer; padding: 11px 0; font-weight: 700; list-style: none; }
details > summary::-webkit-details-marker { display: none; }
details > summary::before { content: "+"; display: inline-grid; place-items: center; width: 22px; height: 22px; margin-right: 8px;
  border-radius: 50%; background: var(--accent-soft); color: var(--accent); font-weight: 800; }
details[open] > summary::before { content: "−"; }
details[open] { padding-bottom: 12px; }
details.why > summary { color: var(--ink); }

/* simulators */
.sim { display: grid; grid-template-columns: 300px 1fr; gap: 20px; align-items: start; }
@media (max-width: 860px) { .sim { grid-template-columns: 1fr; } }
.controls { display: flex; flex-direction: column; gap: 12px; background: var(--bg-2); border-radius: 14px; padding: 14px; }
.ctrl label { display: block; font-size: .9rem; color: var(--sub); font-weight: 600; }
.ctrl label select { float: right; }
.ctrl label output { float: right; color: var(--ink); font-family: var(--mono); font-weight: 700; }
.ctrl .row { display: flex; align-items: center; gap: 8px; }
.ctrl .row input[type="number"] { width: 5.5em; padding: 3px 6px; }
canvas { display: block; width: 100%; border-radius: 14px; background: var(--bg-2); border: 2px solid var(--line); touch-action: none; }
.cv-river { height: 380px; }
.cv-proj { height: 400px; }
.cv-small { height: 170px; }
.cv-vec { height: 360px; }
.cv-esc { height: 200px; }
.readout { display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: 8px; margin-top: 12px; }
.readout div { background: var(--bg-2); border-radius: 12px; padding: 8px 12px; font-size: .85rem; color: var(--sub); font-weight: 600; }
.readout b { display: block; font-family: var(--mono); color: var(--ink); font-size: 1.02rem; }
.legend { display: flex; flex-wrap: wrap; gap: 14px; font-size: .85rem; color: var(--sub); margin-top: 10px; font-weight: 600; }
.legend i { display: inline-block; width: 18px; height: 4px; border-radius: 2px; vertical-align: middle; margin-right: 6px; }
.presets { display: flex; flex-wrap: wrap; gap: 6px; }
.presets button { font-size: .8rem; padding: 4px 10px; border-radius: 10px; box-shadow: 0 2px 0 var(--edge); }
.explain { font-size: .93rem; color: var(--sub); margin-top: 10px; }
.explain b { color: var(--ink); }
.small-plots { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; margin-top: 14px; }
@media (max-width: 860px) { .small-plots { grid-template-columns: 1fr; } }
.small-plots figcaption { font-size: .82rem; color: var(--sub); margin-top: 6px; }
figure { margin: 0; }

/* exercises */
.ex { background: var(--panel); border: 2px solid var(--line); border-radius: 20px; padding: 22px; margin: 20px 0; box-shadow: 0 4px 0 var(--line); }
.ex-head { display: flex; justify-content: space-between; align-items: baseline; gap: 12px; flex-wrap: wrap; }
.ex-head h3 { margin: 0; font-size: 1.25rem; }
.tag { font-size: .74rem; padding: 3px 10px; border-radius: 999px; background: var(--accent-soft); color: var(--accent); font-weight: 800; white-space: nowrap; letter-spacing: .02em; }
.statement { margin: 12px 0; font-size: 1.02rem; }
.statement p:last-child { margin-bottom: 0; }
.data { display: flex; flex-wrap: wrap; gap: 6px; margin: 10px 0 4px; }
.data span { font-family: var(--mono); font-size: .85rem; background: var(--bg-2); border: 2px solid var(--line); padding: 2px 10px; border-radius: 999px; }
.checks { display: flex; flex-direction: column; gap: 10px; margin: 16px 0; padding: 16px; background: var(--bg-2); border-radius: 14px; }
.check { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; font-size: .95rem; font-weight: 600; }
.check .lbl { min-width: 14em; }
.check .unit { color: var(--sub); font-family: var(--mono); font-size: .9rem; }
.fb { font-size: .85rem; font-weight: 800; border-radius: 999px; }
.fb.ok, .fb.bad, .fb.close { padding: 3px 12px; }
.fb.ok { color: var(--ok); background: var(--ok-soft); }
.fb.bad { color: var(--bad); background: var(--bad-soft); }
.fb.close { color: var(--warn); background: var(--warn-soft); }
.check:has(.fb.ok) input { border-color: var(--go); }
.check:has(.fb.bad) input { border-color: var(--bad); }
.step { border-top: 2px dashed var(--line); padding-top: 12px; margin-top: 12px; }
.step:first-child { border-top: 0; margin-top: 0; padding-top: 0; }
.step h4 { margin: 0 0 6px; font-size: 1rem; }
.answer { font-weight: 800; color: var(--ok); background: var(--ok-soft); padding: 1px 8px; border-radius: 8px; }
.sheet-note { font-size: .88rem; color: var(--warn); font-weight: 600; }

/* true / false */
.tf { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 14px; margin: 14px 0; }
.tf-card { background: var(--panel); border: 2px solid var(--line); border-radius: 16px; padding: 16px 18px; display: flex; flex-direction: column; gap: 10px; box-shadow: 0 3px 0 var(--line); }
.tf-card p { margin: 0; font-weight: 600; }
.tf-card .btnrow { margin: 0; }
.tf-card .exp { font-size: .9rem; color: var(--sub); display: none; }
.tf-card.done .exp { display: block; }
.tf-card.right { border-color: var(--go); background: var(--ok-soft); box-shadow: 0 3px 0 var(--go-edge); }
.tf-card.wrong { border-color: var(--bad); background: var(--bad-soft); box-shadow: 0 3px 0 var(--bad); }

/* practice */
.practice-q { font-size: 1.08rem; }
.score { font-family: var(--mono); color: var(--sub); font-weight: 700; align-self: center; }

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation: none !important; transition: none !important; }
}

/* ======================================================================
   2026-11-04 (b): colour per kind of lesson, livelier home, exercise cards, the toolbox ("Eines")
   ====================================================================== */
[data-k] { --k: var(--accent); --k-soft: var(--accent-soft); }
[data-k="teoria"] { --k: var(--k-teoria); --k-soft: var(--k-teoria-soft); }
[data-k="simulador"] { --k: var(--k-simulador); --k-soft: var(--k-simulador-soft); }
[data-k="exercicis"] { --k: var(--k-exercicis); --k-soft: var(--k-exercicis-soft); }
[data-k="practica"] { --k: var(--k-practica); --k-soft: var(--k-practica-soft); }
[data-k="resum"] { --k: var(--k-resum); --k-soft: var(--k-resum-soft); }

/* lesson header: icon tile + "Lliçó n de N", kicker in the lesson's colour */
.lesson-head { display: flex; align-items: center; gap: 12px; margin: 6px 0 14px; }
.lesson-icon { width: 54px; height: 54px; border-radius: 16px; display: grid; place-items: center; font-size: 1.6rem;
  background: var(--k-soft); box-shadow: inset 0 0 0 2px color-mix(in srgb, var(--k) 30%, transparent), 0 4px 0 color-mix(in srgb, var(--k) 35%, transparent); }
.lesson-num { font-weight: 800; color: var(--k); font-size: .9rem; letter-spacing: .02em; }
section.block[data-k] > .kicker { display: inline-block; color: var(--k); background: var(--k-soft); padding: 3px 10px; border-radius: 999px; }
section.block[data-k] > h2 { font-size: clamp(1.8rem, 4vw, 2.6rem); letter-spacing: -.025em; }
section.block[data-k] .note { background: var(--k-soft); }
section.block[data-k] .tag { background: var(--k-soft); color: var(--k); }

/* path + side list in each lesson's colour */
.path li[data-k]:not(.done):not(.next) .node { background: var(--k-soft); border-color: color-mix(in srgb, var(--k) 45%, var(--edge)); box-shadow: 0 5px 0 color-mix(in srgb, var(--k) 45%, var(--edge)); }
.path .lbl span { color: var(--k, var(--sub)); }
.path::before { content: ""; position: absolute; left: 34px; top: 40px; bottom: 40px; width: 4px; border-radius: 2px;
  background: repeating-linear-gradient(var(--line) 0 10px, transparent 10px 18px); z-index: -1; }
@media (min-width: 521px) { .path::before { display: none; } }
.side li[data-k].cur a { background: var(--k-soft); }
.side li[data-k].cur .dot { border-color: var(--k); color: var(--k); }
.lesson-bar a.cur { background: var(--k, var(--accent)); }

/* exercise cards: a tinted head band and aligned answer rows */
.ex { padding: 0 22px 22px; overflow: hidden; }
.ex-head { margin: 0 -22px 14px; padding: 16px 22px 14px; background: var(--k-soft, var(--bg-2)); align-items: center; }
.ex-head h3 { font-size: 1.3rem; }
.ex .statement { font-size: 1.04rem; }
.checks { border: 2px solid var(--line); background: var(--bg-2); }
@media (min-width: 640px) {
  .check { display: grid; grid-template-columns: minmax(0, 17em) 8em 3.2em auto; align-items: center; gap: 10px; }
  .check .lbl { min-width: 0; }
  .check .fb { justify-self: start; }
}
.check input[type="text"] { width: 100%; max-width: 9em; }
.ex .btnrow button.primary { padding-left: 22px; padding-right: 22px; }

/* home */
.home-hero { position: relative; }
.home-hero::before { content: ""; position: absolute; z-index: -1; inset: 10px 0 auto auto; width: min(520px, 100%); height: 420px; border-radius: 50%;
  background: radial-gradient(closest-side, var(--accent-soft), transparent); opacity: .9; max-width: 100vw; }
body { overflow-x: clip; }
.home-hero h1 em { background: linear-gradient(transparent 62%, color-mix(in srgb, var(--c-phys) 70%, transparent) 62%); padding: 0 .06em; color: var(--accent); }
.feature-row { grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); }
.feature { border: 2px solid transparent; transition: transform .12s ease, border-color .12s ease; }
.feature:hover { transform: translateY(-2px); border-color: var(--line); }
.feature .ico { border: 0; width: 48px; height: 48px; font-size: 1.4rem; }
.feature:nth-child(1) .ico { background: var(--k-simulador-soft); }
.feature:nth-child(2) .ico { background: var(--k-exercicis-soft); }
.feature:nth-child(3) .ico { background: var(--k-teoria-soft); }
.feature:nth-child(4) .ico { background: var(--k-practica-soft); }
.topic .meta { flex-wrap: wrap; gap: 6px; }
.topic .meta span { white-space: nowrap; background: var(--bg-2); border-radius: 999px; padding: 2px 10px; }

/* ---------- the toolbox ---------- */
.tools-launch {
  position: fixed; right: 18px; bottom: 18px; z-index: 40; display: inline-flex; align-items: center; gap: 8px;
  font-size: 1rem; padding: 11px 18px; border-radius: 999px;
  background: var(--btn); color: var(--btn-ink); border-color: var(--btn); box-shadow: 0 4px 0 var(--btn-edge), 0 10px 24px rgba(0,0,0,.18);
}
.tools-launch:hover { background: color-mix(in srgb, var(--btn) 88%, var(--bg)); }
body.tools-open .tools-launch { display: none; }

.tools {
  position: fixed; z-index: 45; background: var(--panel); display: flex; flex-direction: column;
  right: 0; top: 0; bottom: 0; width: 400px; border-left: 2px solid var(--line); box-shadow: -10px 0 30px rgba(0,0,0,.08);
}
.tools[hidden] { display: none !important; }
@media (min-width: 1000px) {
  body.tools-open { padding-right: 400px; }
  body.tools-open .course { grid-template-columns: minmax(0, 1fr); gap: 0; }
  body.tools-open .side { display: none; }
  body.tools-open .course-hero { grid-template-columns: 1fr; }
  body.tools-open .course-card { position: static; }
}
@media (max-width: 999px) {
  .tools { top: auto; left: 0; width: auto; height: min(62vh, 560px); border-left: 0; border-top: 2px solid var(--line);
    border-radius: 20px 20px 0 0; box-shadow: 0 -10px 30px rgba(0,0,0,.14); }
  body.tools-open { padding-bottom: min(62vh, 560px); }
}
.tools-head { display: flex; align-items: center; gap: 10px; padding: 12px 14px 6px 18px; }
.tools-head b { font-size: 1.15rem; }
.tools-hint { color: var(--sub); font-size: .78rem; font-weight: 600; flex: 1; line-height: 1.2; }
.tools-close { padding: 4px 11px; border-radius: 10px; font-size: .95rem; }
.tools-tabs { display: grid; grid-template-columns: repeat(4, 1fr); gap: 6px; padding: 6px 14px 10px; border-bottom: 2px solid var(--line); }
.tools-tab { padding: 6px 4px; font-size: .8rem; border-radius: 12px; display: flex; flex-direction: column; align-items: center; gap: 0; line-height: 1.2; }
.tools-tab > span:first-child { font-size: 1.15rem; }
.tools-tab.on { background: var(--accent-soft); border-color: var(--accent); box-shadow: 0 3px 0 var(--accent-edge); }
@media (max-width: 380px) { .tools-tab .tl { font-size: .7rem; } .tools-hint { display: none; } }
.tools-body { flex: 1; overflow-y: auto; padding: 14px 16px 22px; overscroll-behavior: contain; }
.tools-sub { font-size: .78rem; font-weight: 800; color: var(--sub); text-transform: uppercase; letter-spacing: .05em; margin: 12px 0 6px; }
.tools-sub:first-child { margin-top: 0; }
.tools-empty { color: var(--sub); font-size: .88rem; margin-top: 12px; }

/* calculator */
.calc-screen { background: var(--bg-2); border: 2px solid var(--line); border-radius: 16px; padding: 10px 12px; }
.calc-top { display: flex; align-items: center; gap: 8px; margin-bottom: 4px; }
.calc-mode { padding: 1px 10px; font-size: .75rem; border-radius: 8px; box-shadow: 0 2px 0 var(--edge); }
.calc-mode.on { background: var(--accent-soft); border-color: var(--accent); box-shadow: 0 2px 0 var(--accent-edge); }
.calc-tip { color: var(--sub); font-size: .72rem; font-weight: 600; }
input.calc-in { width: 100%; font-family: var(--mono); font-size: 1.15rem; padding: 6px 2px; border: 0; background: transparent; }
input.calc-in:focus { outline: none; }
.calc-out { font-family: var(--mono); font-weight: 800; font-size: 1.6rem; text-align: right; overflow-x: auto; white-space: nowrap; min-height: 1.4em; }
.calc-out.err { color: var(--bad); font-size: .95rem; font-family: var(--sans); white-space: normal; }
.calc-pad { display: grid; grid-template-columns: repeat(4, 1fr); gap: 7px; margin-top: 12px; }
.calc-pad .k { padding: 9px 0; font-size: .95rem; border-radius: 12px; box-shadow: 0 3px 0 var(--edge); }
.calc-pad .k-d { background: var(--bg-2); font-size: 1.1rem; }
.calc-pad .k-op { background: var(--accent-soft); color: var(--accent); font-size: 1.2rem; border-color: color-mix(in srgb, var(--accent) 35%, var(--edge)); }
.calc-pad .k-fn { color: var(--bad); }
.calc-pad .k-eq { grid-column: span 4; background: var(--btn); color: var(--btn-ink); border-color: var(--btn); box-shadow: 0 3px 0 var(--btn-edge); font-size: 1.2rem; }
.calc-send-row { display: flex; align-items: center; flex-wrap: wrap; gap: 10px; margin-top: 12px; }
.calc-target { color: var(--sub); font-size: .82rem; font-weight: 700; min-width: 0; }
.calc-hist { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: 4px; }
.calc-hist li { display: flex; justify-content: space-between; gap: 8px; }
.calc-hist button { border: 0; box-shadow: none; padding: 3px 6px; background: none; font-family: var(--mono); font-size: .85rem; font-weight: 600; border-radius: 8px; text-align: left; }
.calc-hist button:hover { background: var(--soft); }
.calc-hist .h-expr { color: var(--sub); overflow: hidden; text-overflow: ellipsis; white-space: nowrap; min-width: 0; }
.calc-hist .h-val { font-weight: 800; white-space: nowrap; }

/* formulas, units */
.tools-formulas .card { margin: 0 0 12px; padding: 14px; }
.tools-formulas .formula { font-size: .88rem; white-space: normal; }
.tools-formulas ul { padding-left: 1.1em; font-size: .9rem; margin: 0; }
.unit-row { margin-bottom: 8px; }
.unit-io { display: grid; grid-template-columns: 1fr auto; gap: 6px; align-items: center; }
.unit-io input { width: 100%; }
.unit-io .unit-eq { grid-column: 1 / -1; text-align: center; color: var(--sub); font-weight: 800; line-height: 1; }

/* board */
.board-bar { display: flex; gap: 6px; align-items: center; margin-bottom: 8px; }
.board-bar .spacer { flex: 1; }
.pen { padding: 5px 9px; border-radius: 10px; box-shadow: 0 2px 0 var(--edge); line-height: 1; }
.pen.on { border-color: var(--accent); box-shadow: 0 2px 0 var(--accent-edge); background: var(--accent-soft); }
.pen .sw { display: block; width: 16px; height: 16px; border-radius: 50%; }
canvas.board { height: 300px; background: var(--panel); cursor: crosshair;
  background-image: radial-gradient(var(--line) 1.2px, transparent 1.2px); background-size: 18px 18px; }

/* tool chips + notes inside an exercise */
.ex-tools { display: flex; flex-wrap: wrap; align-items: center; gap: 6px; margin: 12px 0 0; }
.ex-tools-l { font-size: .8rem; font-weight: 800; color: var(--sub); margin-right: 2px; }
.chip { font-size: .82rem; padding: 4px 11px; border-radius: 999px; box-shadow: 0 2px 0 var(--edge); }
.chip.on { background: var(--k-soft, var(--accent-soft)); border-color: var(--k, var(--accent)); box-shadow: 0 2px 0 var(--k, var(--accent-edge)); }
.notes-wrap { margin: 10px 0 0; padding: 12px 14px; border-radius: 14px; background: #fffbe6; border: 2px solid #f1e3a1; }
.notes-title { font-size: .88rem; margin-bottom: 6px; color: #5d4a00; }
.notes-title span { font-weight: 600; }
.notes { display: flex; flex-direction: column; gap: 4px; }
.notes-ta { font: inherit; font-size: .95rem; width: 100%; min-height: 6em; resize: vertical; padding: 8px 10px; border-radius: 10px;
  border: 2px solid var(--edge); background: var(--panel); color: var(--ink); line-height: 1.5; }
.notes-wrap .notes-ta { background: transparent; border-color: transparent;
  background-image: repeating-linear-gradient(transparent 0 calc(1.5em + 0px), #efdf96 calc(1.5em) calc(1.5em + 1px)); background-attachment: local; background-position: 0 8px; }
.notes-ta:focus { outline: none; border-color: var(--accent); }
.notes-st { font-size: .75rem; color: var(--sub); font-weight: 600; min-height: 1.1em; }
@media (prefers-color-scheme: dark) {
  .notes-wrap { background: #2b2610; border-color: #4a3f12; }
  .notes-title { color: #f3dc7a; }
  .notes-wrap .notes-ta { background-image: repeating-linear-gradient(transparent 0 1.5em, #4a3f12 1.5em calc(1.5em + 1px)); }
}
.data .data-pick { cursor: pointer; transition: background .12s ease, border-color .12s ease; }
.data .data-pick:hover, .data .data-pick:focus-visible { border-color: var(--accent); background: var(--accent-soft); outline: none; }
section.block[data-k] .ex-head .tag { background: var(--panel); }
.calc-hist-wrap { margin-top: 16px; }