:root {
  --paper: #f3f6f8; --panel: #ffffff; --ink: #132030; --muted: #566578; --rule: #d5dde5; --soft: #e8eef3;
  --v: #c06400; --i: #6a3fd2; --c: #1f5fd6; --p: #0e8478; --q: #c42b6b; --line: #132030;
  --ok: #13843c; --warn: #a86a00; --bad: #c42b2b;
  --ok-bg: #e5f4ea; --warn-bg: #fbf0dc; --bad-bg: #fbe7e7;
  --shadow-sm: 0 1px 2px rgba(19,32,48,.05), 0 1px 1px rgba(19,32,48,.03);
  --ease: cubic-bezier(.2,.7,.2,1);
  --f-display: "Archivo", "Helvetica Neue", Arial, sans-serif;
  --f-body: "IBM Plex Sans", system-ui, -apple-system, "Segoe UI", sans-serif;
  --f-mono: "IBM Plex Mono", ui-monospace, Menlo, Consolas, monospace;
  --f-math: "STIX Two Text", "Cambria Math", "Times New Roman", serif;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --paper: #0e141a; --panel: #141d25; --ink: #e2eaf0; --muted: #93a3b2; --rule: #26333f; --soft: #1a2530;
    --v: #f2a93b; --i: #ab8dff; --c: #70a9ff; --p: #3cc9b9; --q: #ff7aa8; --line: #e2eaf0;
    --ok: #4fd483; --warn: #f2b33b; --bad: #ff7d7d;
    --ok-bg: #12291c; --warn-bg: #2d230f; --bad-bg: #2f1515;
    --shadow-sm: 0 1px 2px rgba(0,0,0,.35);
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --paper: #0e141a; --panel: #141d25; --ink: #e2eaf0; --muted: #93a3b2; --rule: #26333f; --soft: #1a2530;
  --v: #f2a93b; --i: #ab8dff; --c: #70a9ff; --p: #3cc9b9; --q: #ff7aa8; --line: #e2eaf0;
  --ok: #4fd483; --warn: #f2b33b; --bad: #ff7d7d;
  --ok-bg: #12291c; --warn-bg: #2d230f; --bad-bg: #2f1515;
  --shadow-sm: 0 1px 2px rgba(0,0,0,.35);
  color-scheme: dark;
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; -webkit-font-smoothing: antialiased; background: var(--paper); color: var(--ink); font-family: var(--f-body); font-size: 16px; line-height: 1.55; }
:focus-visible { outline: 2px solid var(--v); outline-offset: 2px; border-radius: 3px; }
var { font-family: var(--f-math); font-style: italic; font-size: 1.08em; }
sub { font-size: .7em; }
.mono { font-family: var(--f-mono); }
[hidden] { display: none !important; }

/* barra superior */
.top { position: sticky; top: 0; z-index: 10; background: color-mix(in srgb, var(--paper) 88%, transparent); backdrop-filter: blur(8px); border-bottom: 1px solid var(--rule); }
.top-in { max-width: 1240px; margin: 0 auto; padding-inline: 20px; display: flex; align-items: center; gap: 16px; height: 54px; }
.brand { font-family: var(--f-display); font-stretch: 112%; font-weight: 700; font-size: 14px; letter-spacing: .02em; display: flex; align-items: center; gap: 8px; min-width: 0; }
.brand span { white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.brand svg { flex: none; color: var(--ink); }
.modes { margin-left: auto; display: flex; gap: 2px; background: var(--soft); border-radius: 8px; padding: 3px; flex: none; }
.modes button { font: 500 13.5px var(--f-body); color: var(--muted); background: transparent; border: 0; border-radius: 6px; padding: 6px 12px; cursor: pointer; white-space: nowrap; }
.modes button[aria-selected="true"] { background: var(--panel); color: var(--ink); font-weight: 600; box-shadow: var(--shadow-sm); }
.icon-btn { flex: none; display: inline-grid; place-items: center; width: 34px; height: 34px; color: var(--muted); background: transparent; border: 1px solid var(--rule); border-radius: 7px; cursor: pointer; }
.icon-btn:hover { color: var(--ink); background: var(--soft); }
.icon-btn svg { width: 16px; height: 16px; }

.wrap { max-width: 1240px; margin: 0 auto; padding-inline: 20px; }
.intro { padding-block: 32px 20px; max-width: 820px; }
.eyebrow { margin: 0 0 6px; font: 600 12px var(--f-mono); letter-spacing: .08em; text-transform: uppercase; color: var(--muted); }
h1 { margin: 0 0 10px; font-family: var(--f-display); font-stretch: 108%; font-weight: 750; font-size: clamp(26px, 3.6vw, 38px); line-height: 1.12; letter-spacing: -.01em; }
.lede { margin: 0; color: var(--muted); font-size: 17px; }
.lede strong { color: var(--ink); }

.grid { display: grid; grid-template-columns: minmax(0, 5fr) minmax(0, 7fr); gap: 20px; align-items: start; padding-bottom: 32px; }
.col { display: grid; gap: 20px; min-width: 0; }
.figs { display: grid; grid-template-columns: 1fr; gap: 20px; }

.card { background: var(--panel); border: 1px solid var(--rule); border-radius: 12px; padding: 18px 20px; box-shadow: var(--shadow-sm); min-width: 0; }
.card-head { display: flex; align-items: center; justify-content: space-between; gap: 10px; margin-bottom: 10px; }
h2 { margin: 0; font-family: var(--f-display); font-stretch: 105%; font-weight: 700; font-size: 16.5px; display: flex; align-items: center; gap: 8px; }
.step { display: inline-grid; place-items: center; width: 22px; height: 22px; border-radius: 50%; background: var(--ink); color: var(--paper); font: 600 12px var(--f-mono); flex: none; }
.tag { font-size: 12.5px; color: var(--muted); background: var(--soft); border-radius: 6px; padding: 3px 8px; white-space: nowrap; }
.badge { font: 600 12px var(--f-body); border-radius: 999px; padding: 3px 10px; white-space: nowrap; }
.badge:empty { display: none; }
.badge.ok { background: var(--ok-bg); color: var(--ok); }
.badge.part { background: var(--warn-bg); color: var(--warn); }

.statement { margin: 0 0 14px; font-size: 16px; }
.statement b { font-family: var(--f-mono); font-weight: 600; font-size: .95em; white-space: nowrap; }
.hint-text { margin: 0 0 12px; color: var(--muted); font-size: 14px; }
.note { margin: 8px 0 0; font-size: 13.5px; color: var(--muted); min-height: 1em; }
.row { display: flex; flex-wrap: wrap; gap: 8px; align-items: end; }

.btn { font: 500 14px var(--f-body); color: var(--ink); background: var(--panel); border: 1px solid var(--rule); border-radius: 8px; padding: 8px 14px; cursor: pointer; transition: background-color .15s, border-color .15s, transform .1s; }
.btn:hover { background: var(--soft); border-color: var(--muted); }
.btn:active { transform: scale(.97); }
.btn.primary { background: var(--ink); color: var(--paper); border-color: var(--ink); font-weight: 600; }
.btn.primary:hover { opacity: .9; }
.btn.ghost { border-color: transparent; color: var(--muted); }
.btn:disabled { opacity: .45; cursor: not-allowed; }

select, input[type="text"] { font: 500 15px var(--f-body); color: var(--ink); background: var(--panel); border: 1px solid var(--rule); border-radius: 8px; padding: 7px 10px; min-width: 0; }
input[type="text"] { font-family: var(--f-mono); }
.field-inline { display: grid; gap: 4px; font-size: 13px; color: var(--muted); }

/* respostes */
.answers { display: grid; gap: 10px; }
.ans { display: grid; grid-template-columns: minmax(110px, 1fr) minmax(0, 150px) 28px; gap: 4px 10px; align-items: center; }
.ans label { font-size: 15px; }
.ans label small { display: block; color: var(--muted); font-size: 12.5px; line-height: 1.3; }
.unit-input { display: flex; align-items: center; border: 1px solid var(--rule); border-radius: 8px; background: var(--panel); overflow: hidden; }
.unit-input:focus-within { outline: 2px solid var(--v); outline-offset: 1px; }
.unit-input input { border: 0; outline: none; width: 100%; padding: 7px 8px; background: transparent; }
.unit-input span { padding: 0 9px; font: 500 13px var(--f-mono); color: var(--muted); background: var(--soft); align-self: stretch; display: grid; place-items: center; min-width: 38px; }
.ans.ok .unit-input { border-color: var(--ok); }
.ans.bad .unit-input { border-color: var(--bad); }
.mark { width: 26px; height: 26px; border-radius: 50%; display: grid; place-items: center; font-weight: 700; font-size: 14px; }
.ans.ok .mark { background: var(--ok-bg); color: var(--ok); }
.ans.bad .mark { background: var(--bad-bg); color: var(--bad); }
.ans .fb { grid-column: 1 / -1; font-size: 13.5px; color: var(--bad); margin: -2px 0 2px; }
.ans .fb:empty { display: none; }
.actions { margin-top: 14px; }

.solution { margin-top: 14px; border-top: 1px dashed var(--rule); padding-top: 12px; }
.solution h3 { margin: 10px 0 6px; font: 600 13px var(--f-mono); text-transform: uppercase; letter-spacing: .06em; color: var(--muted); }
.solution ol { margin: 0; padding-left: 20px; display: grid; gap: 5px; }
.solution li { font-size: 15px; }
.solution .res { font-family: var(--f-mono); font-weight: 600; font-size: .93em; }

/* exploració */
.sliders { display: grid; gap: 14px; }
.slider { display: grid; gap: 4px; font-size: 14px; }
.slider > span { display: flex; justify-content: space-between; gap: 10px; align-items: baseline; }
.slider output { font: 600 14px var(--f-mono); }
input[type="range"] { width: 100%; accent-color: var(--v); }
.need { margin-top: 16px; display: grid; grid-template-columns: 1fr 1fr; gap: 10px; background: var(--soft); border-radius: 10px; padding: 12px; }
.need > div { display: grid; }
.need .k { font-size: 12.5px; color: var(--muted); }
.need .v { font-size: 18px; font-weight: 600; }
.need .btn { grid-column: 1 / -1; }

.theory summary { cursor: pointer; list-style: none; display: flex; align-items: center; justify-content: space-between; }
.theory summary::-webkit-details-marker { display: none; }
.theory summary::after { content: "+"; font: 500 20px var(--f-mono); color: var(--muted); }
.theory details[open] summary::after { content: "−"; }
.formulas { margin: 12px 0 0; padding-left: 18px; display: grid; gap: 6px; font-size: 15px; }

/* figures */
.fig { width: 100%; height: auto; display: block; font-family: var(--f-body); }
.fig text { fill: var(--ink); font-size: 13px; }
#circuit text:not([font-size]) { font-size: 14px; }
.fig .muted { fill: var(--muted); }
.fig .mono { font-family: var(--f-mono); }
.fig .math { font-family: var(--f-math); font-style: italic; font-size: 15px; }

/* banc */
.lock { display: flex; gap: 10px; align-items: flex-start; background: var(--soft); color: var(--muted); border-radius: 10px; padding: 12px 14px; font-size: 14px; margin-bottom: 4px; }
.lock svg { width: 18px; height: 18px; flex: none; margin-top: 2px; }
.bench.locked #bench-body { opacity: .35; pointer-events: none; filter: grayscale(1); }
.cap-buttons { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 12px; }
.cap-buttons .btn { font-family: var(--f-mono); font-size: 13.5px; padding: 7px 10px; }
.cap-buttons .btn::before { content: "+ "; color: var(--c); font-weight: 700; }
.custom { margin-bottom: 12px; }
.row.open { margin-top: 14px; padding-top: 14px; border-top: 1px dashed var(--rule); }
.row.open input { width: 140px; }
.open-help { margin: 6px 0 0; font-size: 13px; }
.custom .unit-input { width: 150px; }
.chips { display: flex; flex-wrap: wrap; gap: 6px; min-height: 34px; padding: 8px; border: 1px dashed var(--rule); border-radius: 10px; }
.chips:empty::before { content: "Cap condensador connectat"; color: var(--muted); font-size: 13.5px; padding: 2px 4px; }
.chip { font: 500 13px var(--f-mono); color: var(--c); background: color-mix(in srgb, var(--c) 12%, transparent); border: 1px solid color-mix(in srgb, var(--c) 35%, transparent); border-radius: 999px; padding: 4px 10px; cursor: pointer; }
.chip:hover { text-decoration: line-through; }
.verdict { margin-top: 12px; border-radius: 10px; padding: 10px 14px; font-size: 14.5px; }
.verdict:empty { display: none; }
.verdict.ok { background: var(--ok-bg); color: var(--ok); }
.verdict.warn { background: var(--warn-bg); color: var(--warn); }
.verdict.bad { background: var(--bad-bg); color: var(--bad); }
.verdict strong { display: block; margin-bottom: 2px; }
.verdict span { color: var(--ink); }

/* mesures */
.meter { margin-bottom: 10px; }
.table-wrap { overflow-x: auto; }
table.meas { width: 100%; border-collapse: collapse; font-size: 14.5px; }
.meas th, .meas td { padding: 7px 8px; text-align: right; border-bottom: 1px solid var(--rule); white-space: nowrap; }
.meas th:first-child, .meas td:first-child { text-align: left; }
.meas thead th { font-weight: 600; color: var(--muted); font-size: 12.5px; }
.meas td { font-family: var(--f-mono); }
.meas td:first-child { font-family: var(--f-body); }
.meas .down { color: var(--ok); }
.meas .up { color: var(--bad); }
.meas .same { color: var(--muted); }
.meas .hid { color: var(--muted); }

.legend { list-style: none; display: flex; flex-wrap: wrap; gap: 6px 14px; margin: 8px 0 0; padding: 0; font-size: 13px; color: var(--muted); }
.legend li { display: flex; align-items: center; gap: 6px; }
.sw { display: inline-block; width: 18px; height: 0; border-top: 3px solid var(--ink); }
.sw.dash { border-top: 2px dashed var(--muted); }
.sw.solid { border-color: var(--p); }
.sw.c { border-color: var(--c); }
.sw.v { border-color: var(--v); }
.sw.i { border-color: var(--i); }
.sw.line { border-color: var(--line); }

.foot { padding-block: 8px 32px; color: var(--muted); font-size: 13px; }

@media (max-width: 960px) {
  .grid { grid-template-columns: 1fr; }
}
@media (max-width: 620px) {
  .wrap, .top-in { padding-inline: 16px; }
  .top-in { gap: 10px; }
  .brand span { display: none; }
  .card { padding: 16px; }
  .ans { grid-template-columns: minmax(0, 1fr) minmax(0, 130px) 26px; }
  .need { grid-template-columns: 1fr; }
}
@media (prefers-reduced-motion: reduce) { * { transition: none !important; } }