/* Learn Arduino — tutorials. Plain, fast, readable; the 3D lab's colours. */
@font-face { font-family: 'Nunito'; src: url('/learn/fonts/nunito.woff2') format('woff2'); font-weight: 200 1000; font-display: swap; }
:root {
  color-scheme: light dark;
  --bg: #F4F6F9; --card: #FFFFFF; --ink: #14202E; --ink-2: #4A5A6E; --line: #DCE3EC;
  --accent: #0E7C86; --accent-2: #0A6A73; --accent-soft: #DDF3F4; --warn: #B45309; --warn-soft: #FFF4E5;
  --code-bg: #0F1B2A; --code-ink: #E3ECF7;
  --radius: 16px; --shadow: 0 8px 24px rgba(20, 32, 46, 0.08);
}
@media (prefers-color-scheme: dark) {
  :root { --bg: #0D1520; --card: #141F2D; --ink: #E6EDF6; --ink-2: #A3B2C5; --line: #243246; --accent: #3CC4CE; --accent-2: #5BD6DE; --accent-soft: #123A40; --warn: #F5B355; --warn-soft: #3A2A12; --code-bg: #0A121C; }
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-padding-top: 80px; }
body { margin: 0; background: var(--bg); color: var(--ink); font: 18px/1.7 'Nunito', system-ui, 'Segoe UI', Roboto, sans-serif; }
a { color: var(--accent); text-underline-offset: 3px; }
img { max-width: 100%; height: auto; }
.skip { position: absolute; left: -999px; top: 8px; background: var(--card); padding: 8px 12px; border-radius: 8px; z-index: 10; }
.skip:focus { left: 8px; }

/* top bar */
.top { position: sticky; top: 0; z-index: 5; display: flex; align-items: center; gap: 16px; padding: 10px 20px; background: color-mix(in srgb, var(--card) 88%, transparent); backdrop-filter: blur(10px); border-bottom: 1px solid var(--line); }
.brand { display: flex; align-items: center; gap: 10px; color: var(--ink); text-decoration: none; font-weight: 900; letter-spacing: .02em; white-space: nowrap; }
.brand small { color: var(--accent); font-weight: 800; margin-left: 4px; }
.top nav { display: flex; gap: 4px; flex: 1; overflow-x: auto; scrollbar-width: none; }
.top nav a { color: var(--ink-2); text-decoration: none; font-weight: 700; font-size: 15px; padding: 12px 10px; min-height: 48px; display: inline-flex; align-items: center; white-space: nowrap; }
.top nav a:hover { color: var(--accent); }
.top__lab { display: inline-flex; align-items: center; min-height: 44px; padding: 0 16px; border-radius: 999px; background: var(--accent); color: #fff; font-weight: 800; font-size: 15px; text-decoration: none; white-space: nowrap; }
.top__lab:hover { background: var(--accent-2); }
.top__lab.big { min-height: 52px; padding: 0 24px; font-size: 17px; margin-top: 8px; }

/* article */
main { max-width: 1120px; margin: 0 auto; padding: 16px 20px 48px; }
.crumbs { font-size: 15px; color: var(--ink-2); margin: 6px 0 14px; }
.crumbs a { color: var(--ink-2); }
.hero { max-width: 780px; }
.kicker { margin: 0; font-size: 14px; font-weight: 800; letter-spacing: .06em; text-transform: uppercase; color: var(--accent); }
h1 { font-size: clamp(2rem, 5vw, 3rem); line-height: 1.12; margin: .3rem 0 .6rem; letter-spacing: -.01em; }
.lead { font-size: 1.2rem; color: var(--ink-2); margin: 0 0 1.2rem; }
.hero__img { margin: 0 0 18px; }
.hero__img img { border-radius: var(--radius); box-shadow: var(--shadow); display: block; width: 100%; }

/* the project live in 3D: a picture with a Play button, then the 3D lab's own view in a frame */
.lab3d { margin: 1.4rem 0; }
.lab3d__frame { position: relative; aspect-ratio: 16 / 10; border-radius: var(--radius); overflow: hidden; background: #E8EDF3; border: 1px solid var(--line); box-shadow: var(--shadow); cursor: pointer; }
.lab3d__frame img { width: 100%; height: 100%; object-fit: cover; display: block; border: 0 !important; border-radius: 0 !important; transition: transform .4s ease, filter .3s ease; }
.lab3d__frame:hover img { transform: scale(1.02); filter: saturate(1.1); }
.lab3d__play { position: absolute; left: 50%; top: 50%; transform: translate(-50%, -50%); display: flex; align-items: center; gap: 12px; min-height: 56px; padding: 10px 20px 10px 10px; border: 0; border-radius: 999px; background: var(--accent); color: #fff; font: inherit; text-align: left; cursor: pointer; box-shadow: 0 10px 30px rgba(14, 124, 134, .45); animation: pulse 2.4s ease-in-out infinite; }
.lab3d__play b { display: block; font-size: 1.1rem; line-height: 1.2; }
.lab3d__play small { display: block; font-size: 13px; opacity: .9; }
.lab3d__icon { display: grid; place-items: center; width: 40px; height: 40px; border-radius: 50%; background: #fff; flex: none; }
.lab3d__icon svg { width: 20px; height: 20px; fill: var(--accent); margin-left: 3px; }
.lab3d__frame.is-live { cursor: auto; }
.lab3d__frame iframe { width: 100%; height: 100%; border: 0; display: block; }
.lab3d figcaption { font-size: 15px; color: var(--ink-2); text-align: center; margin-top: 6px; }
@keyframes pulse { 0%, 100% { box-shadow: 0 10px 30px rgba(14, 124, 134, .45); } 50% { box-shadow: 0 10px 30px rgba(14, 124, 134, .45), 0 0 0 10px rgba(14, 124, 134, .15); } }
@media (prefers-reduced-motion: reduce) { .lab3d__play { animation: none; } .lab3d__frame img { transition: none; } }
@media (max-width: 640px) { .lab3d__frame { aspect-ratio: 4 / 5; } .lab3d__play small { display: none; } }
.hero__img .lab3d { margin: 0 0 18px; }

.try { display: flex; align-items: center; gap: 14px; margin: 18px 0; padding: 14px 18px; border-radius: var(--radius); background: var(--accent-soft); border: 1px solid color-mix(in srgb, var(--accent) 30%, transparent); color: var(--ink); text-decoration: none; }
.try:hover { border-color: var(--accent); }
.try__icon svg { width: 34px; height: 34px; fill: none; stroke: var(--accent); stroke-width: 1.8; stroke-linejoin: round; }
.try b { display: block; font-size: 1.05rem; }
.try small { display: block; color: var(--ink-2); font-size: 15px; line-height: 1.4; }
.try__go { margin-left: auto; font-weight: 900; color: var(--accent); white-space: nowrap; }

.share { display: flex; flex-wrap: wrap; gap: 8px; margin: 8px 0 18px; }
.share__btn { display: inline-flex; align-items: center; gap: 6px; min-height: 44px; padding: 0 14px; border-radius: 999px; border: 1px solid var(--line); background: var(--card); color: var(--ink); font: inherit; font-size: 15px; font-weight: 700; text-decoration: none; cursor: pointer; }
.share__btn:hover { border-color: var(--accent); color: var(--accent); }
.share__btn svg { width: 18px; height: 18px; fill: none; stroke: currentColor; stroke-width: 2; stroke-linecap: round; }

.layout { display: grid; grid-template-columns: 1fr; gap: 32px; }
@media (min-width: 1000px) { .layout { grid-template-columns: 220px minmax(0, 780px); } }
.toc { font-size: 15px; }
@media (min-width: 1000px) { .toc { position: sticky; top: 84px; align-self: start; } }
.toc b { display: block; text-transform: uppercase; font-size: 13px; letter-spacing: .06em; color: var(--ink-2); margin-bottom: 6px; }
.toc ol { list-style: none; margin: 0; padding: 0; border-left: 2px solid var(--line); }
.toc li a { display: block; padding: 6px 12px; color: var(--ink-2); text-decoration: none; line-height: 1.35; }
.toc li a:hover { color: var(--accent); }
@media (max-width: 999px) { .toc { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 12px 14px; } }

.prose { min-width: 0; }
.prose h2 { font-size: 1.6rem; line-height: 1.25; margin: 2.2rem 0 .6rem; }
.prose h3 { font-size: 1.22rem; margin: 1.6rem 0 .4rem; }
.prose h2 .anchor, .prose h3 .anchor { float: left; margin-left: -1em; padding-right: .3em; color: var(--line); text-decoration: none; opacity: 0; }
.prose h2:hover .anchor, .prose h3:hover .anchor { opacity: 1; }
.prose p, .prose li { margin: .55rem 0; }
.prose li::marker { color: var(--accent); font-weight: 800; }
.prose figure { margin: 1.4rem 0; }
.prose figure img { border-radius: 12px; border: 1px solid var(--line); display: block; margin: 0 auto; background: var(--card); }
.prose figcaption { font-size: 15px; color: var(--ink-2); text-align: center; margin-top: 6px; }
.prose code { font: .88em/1.4 ui-monospace, 'Cascadia Code', Consolas, monospace; background: var(--accent-soft); padding: .1em .35em; border-radius: 6px; }
.code { background: var(--code-bg); color: var(--code-ink); border-radius: 14px; padding: 16px 18px; overflow-x: auto; font: 15px/1.6 ui-monospace, 'Cascadia Code', Consolas, monospace; position: relative; }
.code code { background: none; padding: 0; font: inherit; }
.code::before { content: attr(data-lang); position: absolute; top: 6px; right: 12px; font-size: 12px; text-transform: uppercase; opacity: .5; letter-spacing: .08em; }
.t-k { color: #FF9D6C; } .t-f { color: #7FD6FF; } .t-n { color: #F7D774; } .t-s { color: #9FE39A; } .t-c { color: #8193A8; font-style: italic; }
.callout { margin: 1.2rem 0; padding: 12px 16px; border-radius: 12px; border-left: 5px solid var(--accent); background: var(--accent-soft); }
.callout--warning, .callout--safety { border-left-color: var(--warn); background: var(--warn-soft); }
.table { overflow-x: auto; margin: 1rem 0; }
table { border-collapse: collapse; width: 100%; font-size: 16px; background: var(--card); border-radius: 12px; overflow: hidden; }
th, td { text-align: left; padding: 9px 12px; border-bottom: 1px solid var(--line); vertical-align: top; }
th { background: var(--accent-soft); font-weight: 800; }
.updated { font-size: 14px; color: var(--ink-2); }

.parts { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 6px 18px 12px; margin: 0 0 1.6rem; box-shadow: var(--shadow); }
.parts h2 { font-size: 1.2rem !important; margin: .8rem 0 .4rem !important; }
.parts ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 4px; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); }
.parts li { display: flex; align-items: center; gap: 10px; margin: 0; padding: 4px 0; font-size: 16px; font-weight: 700; line-height: 1.3; }
.parts img { width: 56px; height: 56px; object-fit: contain; flex: none; }
.parts__dot { width: 56px; height: 12px; flex: none; display: grid; place-items: center; }
.parts__dot::after { content: ''; width: 10px; height: 10px; border-radius: 50%; background: var(--accent); }
.parts__buy { margin-left: auto; font-size: 14px; font-weight: 800; padding: 6px 12px; border-radius: 999px; border: 1px solid var(--accent); text-decoration: none; }
.parts__note { font-size: 14px; color: var(--ink-2); margin: .6rem 0 0; }

/* cards (hub, read next) */
.more { margin-top: 40px; }
.more h2 { font-size: 1.5rem; }
.cards { display: grid; gap: 16px; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); }
.card { display: flex; flex-direction: column; background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); overflow: hidden; color: var(--ink); text-decoration: none; box-shadow: var(--shadow); transition: transform .15s ease, border-color .15s ease; }
.card:hover { transform: translateY(-3px); border-color: var(--accent); }
.card img { aspect-ratio: 16 / 10; object-fit: cover; width: 100%; background: var(--accent-soft); }
.card__body { padding: 12px 16px 16px; display: flex; flex-direction: column; gap: 4px; }
.card__body small { color: var(--accent); font-weight: 800; font-size: 13px; text-transform: uppercase; letter-spacing: .05em; }
.card__body b { font-size: 1.15rem; line-height: 1.3; }
.card__body span { color: var(--ink-2); font-size: 15px; line-height: 1.45; }
.pager { display: flex; justify-content: space-between; gap: 16px; margin-top: 40px; }
.pager a { flex: 1; max-width: 48%; padding: 14px 18px; background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); text-decoration: none; color: var(--ink); font-weight: 800; }
.pager a small { display: block; color: var(--ink-2); font-weight: 700; }
.pager__next { text-align: right; margin-left: auto; }
.hub__hero { max-width: 760px; padding: 20px 0 8px; }

.foot { border-top: 1px solid var(--line); padding: 24px 20px 40px; text-align: center; color: var(--ink-2); font-size: 15px; }
.foot__small { font-size: 14px; }
@media (max-width: 640px) {
  body { font-size: 17px; }
  .top { gap: 8px; padding: 8px 12px; }
  .brand small, .top nav { display: none; }
  .top__lab { margin-left: auto; }
  main { padding: 12px 16px 40px; }
  .try { flex-wrap: wrap; }
  .try__go { margin-left: 48px; }
  .pager { flex-direction: column; } .pager a { max-width: none; }
}
/* the "Try it in 3D" box keeps its icon and words on one line on a phone; the button wraps below */
.try > span:nth-child(2) { flex: 1 1 220px; min-width: 0; }

/* "Check yourself" quiz */
.quiz { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 6px 18px 12px; box-shadow: var(--shadow); }
.quiz ol { margin: 0; padding-left: 1.2em; }
.quiz__ask { font-weight: 800; margin: 1rem 0 .4rem; }
.quiz__answers { display: grid; gap: 8px; }
.quiz__a { text-align: left; min-height: 48px; padding: 10px 14px; border-radius: 12px; border: 1px solid var(--line); background: var(--bg); color: var(--ink); font: inherit; font-size: 16px; cursor: pointer; }
.quiz__a:hover:not(:disabled) { border-color: var(--accent); }
.quiz__a:disabled { cursor: default; }
.quiz__a.is-right { border-color: #16A34A; background: color-mix(in srgb, #16A34A 14%, var(--card)); font-weight: 800; }
.quiz__a.is-wrong { border-color: #DC2626; background: color-mix(in srgb, #DC2626 12%, var(--card)); }
.quiz__a.is-right::before { content: '✓ '; color: #16A34A; } .quiz__a.is-wrong::before { content: '✗ '; color: #DC2626; }
.quiz__why { font-size: 15px; color: var(--ink-2); margin: .5rem 0 0; }
.quiz__score { font-weight: 800; color: var(--accent); margin: .8rem 0 0; }

/* reading progress */
.readbar { position: fixed; left: 0; right: 0; top: 0; height: 3px; z-index: 10; pointer-events: none; }
.readbar span { display: block; height: 100%; width: 0; background: var(--accent); transition: width .1s linear; }
/* copy code */
.code__copy { position: absolute; top: 8px; right: 8px; min-height: 36px; padding: 0 12px; border-radius: 10px; border: 1px solid rgba(255,255,255,.2); background: rgba(255,255,255,.08); color: var(--code-ink); font: 700 13px 'Nunito', system-ui, sans-serif; cursor: pointer; }
.code__copy:hover { background: rgba(255,255,255,.18); }
.code::before { right: auto; left: 16px; top: auto; bottom: 6px; }
/* done + next */
.done { margin: 1.6rem 0; padding: 16px; border-radius: var(--radius); background: var(--card); border: 1px solid var(--line); display: flex; flex-wrap: wrap; align-items: center; gap: 12px; }
.done__btn { display: inline-flex; align-items: center; gap: 10px; min-height: 48px; padding: 0 18px; border-radius: 999px; border: 2px solid var(--accent); background: transparent; color: var(--accent); font: inherit; font-weight: 800; cursor: pointer; }
.done__tick { display: grid; place-items: center; width: 24px; height: 24px; border-radius: 50%; border: 2px solid currentColor; font-size: 14px; }
.done__btn.is-on { background: var(--accent); color: #fff; }
.done__next { margin-left: auto; font-weight: 800; text-decoration: none; }
.done__note { width: 100%; margin: 0; font-size: 14px; color: var(--ink-2); }
/* embed */
.embed { margin: 1.6rem 0; padding: 4px 18px 16px; border-radius: var(--radius); border: 1px dashed var(--accent); background: var(--accent-soft); }
.embed h2 { font-size: 1.2rem !important; margin: .8rem 0 .2rem !important; }
.embed__code { white-space: pre-wrap; word-break: break-all; font: 13px/1.5 ui-monospace, Consolas, monospace; background: var(--card); border-radius: 10px; padding: 10px 12px; margin: .6rem 0; }
.embed__code code { background: none !important; padding: 0 !important; }
/* hub */
.hub__live { max-width: 900px; }
.start { margin-top: 28px; }
.start h2, .more h2 { font-size: 1.5rem; }
.more h2 small { font-size: 1rem; color: var(--ink-2); font-weight: 700; }
.start__path { list-style: none; margin: 0; padding: 0; display: grid; gap: 10px; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); counter-reset: s; }
.start__path a { display: flex; align-items: center; gap: 12px; min-height: 64px; padding: 10px 14px; border-radius: 14px; background: var(--card); border: 1px solid var(--line); color: var(--ink); text-decoration: none; }
.start__path a:hover { border-color: var(--accent); }
.start__path a.is-done .start__n { background: #16A34A; }
.start__path a.is-done .start__n::after { content: '✓'; } .start__path a.is-done .start__n { font-size: 0; } .start__path a.is-done .start__n::after { font-size: 16px; }
.start__n { flex: none; display: grid; place-items: center; width: 36px; height: 36px; border-radius: 50%; background: var(--accent); color: #fff; font-weight: 900; }
.start__path b { display: block; line-height: 1.25; } .start__path small { color: var(--ink-2); }
.start__progress { font-weight: 800; color: var(--accent); }
.finder { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; margin-top: 28px; position: sticky; top: 70px; z-index: 3; padding: 8px 0; background: var(--bg); }
.finder__search { flex: 1 1 260px; }
.finder__search input { width: 100%; min-height: 48px; padding: 0 16px; border-radius: 999px; border: 1px solid var(--line); background: var(--card); color: var(--ink); font: inherit; }
.finder__search input:focus { outline: 2px solid var(--accent); outline-offset: 1px; }
.finder__chips { display: flex; gap: 6px; }
.chip { min-height: 44px; padding: 0 16px; border-radius: 999px; border: 1px solid var(--line); background: var(--card); color: var(--ink); font: inherit; font-weight: 800; font-size: 15px; cursor: pointer; }
.chip.is-on { background: var(--accent); border-color: var(--accent); color: #fff; }
.visually-hidden { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
.card { position: relative; }
.card__art { aspect-ratio: 16 / 10; background: linear-gradient(135deg, var(--accent-soft), var(--card)); }
.card__done { position: absolute; top: 10px; right: 10px; display: none; padding: 4px 10px; border-radius: 999px; background: #16A34A; color: #fff; font-weight: 800; font-size: 13px; }
.card.is-done .card__done { display: block; }
.card[hidden], [data-group][hidden] { display: none; }
/* card pictures: the component on its own, on a soft backdrop (never the whole bench) */
.card__art { display: grid; place-items: center; aspect-ratio: 16 / 10; background: radial-gradient(circle at 50% 45%, var(--card), var(--accent-soft) 85%); overflow: hidden; }
.card__art img { width: 72%; height: 88%; object-fit: contain; aspect-ratio: auto; background: none; filter: drop-shadow(0 10px 14px rgba(20, 32, 46, .18)); transition: transform .25s ease; }
.card:hover .card__art img { transform: scale(1.06) rotate(-2deg); }
@media (prefers-reduced-motion: reduce) { .card:hover .card__art img { transform: none; } }
/* a component article's top picture: the part on its own */
.hero__part { display: grid; place-items: center; aspect-ratio: 16 / 9; border-radius: var(--radius); background: radial-gradient(circle at 50% 45%, var(--card), var(--accent-soft) 80%); box-shadow: var(--shadow); }
.hero__part img { width: 56% !important; height: 86%; object-fit: contain; box-shadow: none !important; border-radius: 0 !important; filter: drop-shadow(0 16px 22px rgba(20, 32, 46, .22)); }