/* Robotics & Arduino — shared presentation theme.
   Change the tokens below to restyle every lesson page.
   Sections: tokens / base / frame / panels / lesson layouts / diagrams / responsive. */

:root {
  color-scheme: dark;
  --color-bg: #101c20;
  --color-surface: #17272c;
  --color-surface-raised: #203239;
  --color-code: #0c171b;
  --color-text: #e6eeeb;
  --color-muted: #a7b9b6;
  --color-accent: #b99aff;
  --color-primary: #703cf0;
  --color-primary-end: #9745ef;
  --color-on-primary: #ffffff;
  --color-water: #62d2cb;
  --color-lamp: #f3ce79;
  --color-border: #30434a;
  --color-grid: #b5d8d807;
  --color-focus: #d8c7ff;
  --radius-panel: 22px;
  --radius-small: 12px;
  --radius-pill: 999px;
  --shadow-panel: 0 16px 50px #00000024;
  --page-gutter: clamp(20px, 5vw, 90px);
  --font-body: "Segoe UI", Arial, sans-serif;
  --font-code: Consolas, "Courier New", monospace;
}

/* Base */
* { box-sizing: border-box; }
body {
  margin: 0;
  background-color: var(--color-bg);
  background-image: linear-gradient(var(--color-grid) 1px, transparent 1px),
                    linear-gradient(90deg, var(--color-grid) 1px, transparent 1px);
  background-size: 28px 28px;
  color: var(--color-text);
  font-family: var(--font-body);
}
::selection { background: var(--color-primary); color: var(--color-on-primary); }
h1 { margin: 0 0 28px; font-size: clamp(38px, 4.3vw, 68px); line-height: 1.1; letter-spacing: -.045em; font-weight: 750; }
h1 span, h2, h3 { color: var(--color-accent); }
h2 { margin: 0 0 20px; font-size: clamp(24px, 2.1vw, 34px); line-height: 1.2; letter-spacing: -.025em; }
h3 { margin: 22px 0 12px; font-size: clamp(20px, 1.8vw, 28px); }
p { line-height: 1.5; }
strong { font-weight: 650; }
ul { margin: 0; padding-left: 1.1em; font-size: clamp(21px, 2.05vw, 33px); line-height: 1.45; font-weight: 500; }
li { padding-left: .25em; margin: 0 0 15px; }
li:last-child { margin-bottom: 0; }
li::marker { color: var(--color-accent); font-size: .85em; }
a { color: var(--color-text); text-decoration: none; }
a:hover { color: var(--color-accent); }
button { font: inherit; cursor: pointer; }
button, footer a {
  display: inline-flex; align-items: center; justify-content: center; gap: 9px;
  padding: 11px 19px; border: 1px solid var(--color-border);
  border-radius: var(--radius-pill); background: var(--color-surface); color: var(--color-text);
  font-weight: 600; line-height: 1.2; transition: background-color .15s, border-color .15s;
}
button:hover, footer a:hover { background: var(--color-surface-raised); border-color: var(--color-accent); color: var(--color-text); }
button[hidden] { display: none; }
:is(a, button, pre):focus-visible { outline: 3px solid var(--color-focus); outline-offset: 4px; }
button svg { width: 17px; height: 17px; }
img, svg { max-width: 100%; }
figure { margin: 0; }

/* Page frame and navigation */
.slide { min-height: 100svh; display: flex; flex-direction: column; padding: 24px var(--page-gutter) 0; }
header { display: flex; justify-content: space-between; align-items: center; gap: 24px; border-bottom: 1px solid var(--color-border); padding-bottom: 19px; }
.brand { display: flex; align-items: center; gap: 12px; font-size: 13px; font-weight: 700; letter-spacing: .12em; text-transform: uppercase; }
.brand svg { width: 34px; height: 34px; color: var(--color-accent); }
.edition { padding: 8px 15px; border: 1px solid var(--color-border); border-radius: var(--radius-pill); background: var(--color-surface); color: var(--color-muted); font-size: 11px; letter-spacing: .1em; text-transform: uppercase; }
main { flex: 1; min-width: 0; display: flex; flex-direction: column; justify-content: center; padding: 36px 0; }
footer { display: flex; justify-content: space-between; align-items: center; gap: 16px; border-top: 1px solid var(--color-border); padding: 17px 0; font-size: 12px; letter-spacing: .04em; color: var(--color-muted); }
footer a[rel="next"] { border-color: transparent; color: var(--color-on-primary); background: linear-gradient(110deg, var(--color-primary), var(--color-primary-end)); }
footer a[rel="next"]:hover { border-color: var(--color-focus); }
.footer-right, .controls { display: flex; align-items: center; gap: 12px; }
.bottom-rule { height: 3px; margin: 0 calc(-1 * var(--page-gutter)); background: linear-gradient(90deg, var(--color-primary), var(--color-water)); }

/* Shared panels and multi-column lessons */
.comparison, .code-layout, .showcase-layout, .contact-layout { display: grid; grid-template-columns: 1fr 1fr; gap: clamp(20px, 2.5vw, 42px); align-items: stretch; }
.comparison > section, .code-layout > section, .robotics, .contact-layout > section,
.page-list main > ul, .wifi, .reset-note, .type-note {
  border: 1px solid var(--color-border); border-radius: var(--radius-panel);
  background: var(--color-surface); box-shadow: var(--shadow-panel);
}
.comparison > section, .code-layout > section, .robotics, .contact-layout > section { padding: clamp(22px, 2.5vw, 38px); min-width: 0; }
.page-list main > ul { padding: 28px 32px 28px 58px; }
.detail, .explanation, .type-note, .intro { color: var(--color-muted); }
.explanation { font-size: .8em; margin: 10px 0 0; }
.page-first-projects li { margin-bottom: 24px; }
.page-first-projects li:last-child { margin-bottom: 0; }
.page-pwm main > ul { font-size: clamp(18px, 1.5vw, 25px); line-height: 1.45; }
.page-pwm li { margin-bottom: 17px; }
.page-pwm li:last-child { margin-bottom: 0; color: var(--color-water); }

/* Lesson directory */
.page-index main { justify-content: flex-start; padding: 28px 0; }
.index-opening { display: flex; flex-wrap: wrap; gap: 10px; list-style: none; padding: 0; margin: 0 0 24px; font-size: 17px; }
.index-opening li { margin: 0; padding: 0; }
.index-opening a { display: block; padding: 10px 17px; border: 1px solid var(--color-border); border-radius: var(--radius-pill); background: var(--color-surface); }
.index-sections { display: grid; grid-template-columns: 1fr 1fr; gap: 24px; }
.index-sections section { padding: 24px; border: 1px solid var(--color-border); border-radius: var(--radius-panel); background: var(--color-surface); min-width: 0; }
.index-sections h2 { font-size: clamp(23px, 2vw, 31px); margin-bottom: 15px; }
.index-sections ul { list-style: none; padding: 0; font-size: clamp(17px, 1.3vw, 22px); line-height: 1.3; }
.index-sections li { padding: 0; margin: 0; border-bottom: 1px solid var(--color-border); }
.index-sections li:last-child { border-bottom: 0; }
.index-sections a { display: block; padding: 10px 8px; border-radius: var(--radius-small); }
.lesson-directory a:hover { background: var(--color-surface-raised); color: var(--color-accent); }
.lesson-directory a[aria-current="page"], .index-button[aria-current="page"] { color: var(--color-accent); border-color: var(--color-accent); }
@media (max-width: 800px) { .index-sections { grid-template-columns: 1fr; } }

/* Cover and section dividers */
.page-cover main { display: grid; grid-template-columns: 1.15fr 1fr; gap: 3vw; align-items: center; padding: 42px 0; }
.page-cover h1 { font-size: clamp(50px, 5.8vw, 91px); line-height: 1.025; letter-spacing: -.055em; margin: 0; }
.eyebrow { margin: 0 0 28px; display: flex; align-items: center; gap: 13px; font-size: 17px; font-weight: 600; }
.number { color: var(--color-on-primary); background: linear-gradient(110deg, var(--color-primary), var(--color-primary-end)); padding: 9px 13px; border-radius: var(--radius-small); font-size: 14px; }
.subtitle { font-size: clamp(23px, 2vw, 31px); margin: 30px 0 0; }
.subtitle span { color: var(--color-muted); }
.page-cover figure { padding: 18px; background: var(--color-surface); border: 1px solid var(--color-border); border-radius: var(--radius-panel); box-shadow: var(--shadow-panel); }
.illustration { width: 100%; max-height: 62vh; display: block; }
.page-divider main { padding-left: 3vw; }
.page-divider h1 { font-size: clamp(42px, 6vw, 100px); }
.presenter, .questions { margin: 0; color: var(--color-accent); font-size: clamp(30px, 3.5vw, 54px); font-weight: 600; }
.page-agenda .contact-layout ul { font-size: clamp(21px, 1.9vw, 30px); }
.page-agenda .contact-layout li { margin-bottom: 18px; }
.page-recap h1 { font-size: clamp(38px, 4.3vw, 68px); }
.recap-points { margin-bottom: 30px; font-size: clamp(20px, 1.9vw, 30px); }
.recap-points strong { color: var(--color-accent); }
.page-recap .questions { font-size: clamp(26px, 2.5vw, 38px); }

/* Showcase and Arduino comparison */
.showcase-layout { grid-template-columns: .85fr 1.15fr; align-items: start; }
.videos { list-style: none; padding: 0; font-size: clamp(26px, 2.8vw, 43px); }
.videos li { margin: 0 0 16px; padding: 0; }
.videos a { display: flex; align-items: center; justify-content: space-between; gap: 20px; padding: 23px 28px; border: 1px solid var(--color-border); border-radius: var(--radius-panel); background: var(--color-surface); }
.videos a:hover { border-color: var(--color-accent); background: var(--color-surface-raised); }
.videos a span { color: var(--color-accent); font-size: .75em; }
.showcase-note { margin: 14px 4px 0; color: var(--color-muted); font-size: clamp(17px, 1.4vw, 23px); line-height: 1.4; }
.robotics p, .robotics ul { font-size: clamp(20px, 1.65vw, 27px); line-height: 1.5; }
.robotics p { margin: 0 0 14px; }
.comparison { grid-template-columns: .8fr 1.2fr; }
.comparison ul { font-size: clamp(20px, 1.85vw, 29px); }

/* Code concepts and copyable sketches */
pre { margin: 0; padding: 20px 26px; border: 1px solid var(--color-border); border-radius: var(--radius-panel); background: var(--color-code); color: var(--color-text); overflow-x: auto; tab-size: 2; }
code { font-family: var(--font-code); }
.code-layout { grid-template-columns: 1.1fr 1fr; }
.code-layout ul { font-size: clamp(19px, 1.55vw, 26px); line-height: 1.4; }
.ideas ul { margin-top: 10px; }
.ideas ul li { margin-bottom: 5px; }
.examples pre { margin: 12px 0 22px; padding: 16px 20px; white-space: pre-wrap; overflow-wrap: anywhere; font-size: clamp(20px, 1.8vw, 28px); line-height: 1.5; border-radius: var(--radius-small); }
.keyword { color: var(--color-accent); font-weight: 700; }
.value { color: var(--color-water); font-weight: 700; }
.type-note { padding: 17px 22px; margin: 20px 0 0; font-size: clamp(16px, 1.3vw, 21px); }
.type-note code { color: var(--color-text); }
.page-sketch main { padding: 22px 0; }
.page-sketch h1 { margin-bottom: 14px; font-size: clamp(36px, 3.8vw, 58px); }
.code-heading { display: flex; align-items: center; flex-wrap: wrap; gap: 12px 20px; margin-bottom: 12px; }
.code-heading p { margin: 0; font-size: clamp(18px, 1.55vw, 25px); }
#copy-code { font-size: 14px; }
#copy-status { color: var(--color-muted); font-size: 14px; }
.page-sketch code { font-size: clamp(13px, 1.1vw, 19px); line-height: 1.45; }
.finish { display: flex; align-items: baseline; justify-content: space-between; flex-wrap: wrap; gap: 12px 24px; margin-top: 18px; }
.finish p { margin: 0; font-size: clamp(18px, 1.6vw, 26px); }
.steps span { color: var(--color-accent); padding: 0 8px; }
.congrats { color: var(--color-water); font-weight: 700; }

/* IDE installation and annotated screenshot */
.wifi { display: flex; flex-wrap: wrap; align-items: center; gap: 14px 32px; padding: 20px 24px; margin: 0 0 28px; font-size: clamp(18px, 1.65vw, 25px); }
.wifi > strong { color: var(--color-accent); }
.password { font-family: var(--font-code); font-variant-numeric: tabular-nums; }
.page-install ul { font-size: clamp(20px, 1.9vw, 30px); }
.page-install li { margin-bottom: 20px; }
.download-link { text-decoration: underline; text-underline-offset: 5px; text-decoration-color: var(--color-accent); overflow-wrap: anywhere; }
.install-steps { margin: 14px 0 8px; font-weight: 650; font-size: .9em; line-height: 1.6; }
.page-ide main { padding: 24px 0 12px; }
.page-ide h1 { margin-bottom: 12px; font-size: clamp(36px, 3.8vw, 58px); }
.intro { margin: 0 0 18px; font-size: clamp(18px, 1.65vw, 26px); line-height: 1.4; }
.intro strong { color: var(--color-text); }
.ide-map { display: block; width: 100%; max-height: 65vh; margin: auto; overflow: visible; background: var(--color-surface); border: 1px solid var(--color-border); border-radius: var(--radius-panel); padding: 12px; }
.leaders { fill: none; stroke: var(--color-accent); stroke-width: 3; stroke-linecap: round; stroke-linejoin: round; }
.targets { fill: none; stroke: var(--color-accent); stroke-width: 3; }
.ide-map .labels { fill: var(--color-text); font: 30px var(--font-body); }
.label-title { fill: var(--color-accent); font-weight: 700; font-size: 35px; }

/* First contact */
.contact-layout { gap: 24px; }
.contact-layout ul, .pin-groups, .pin-note, .reset-note p { font-size: clamp(18px, 1.55vw, 25px); line-height: 1.4; }
.contact-layout li { margin-bottom: 10px; padding-left: .15em; }
.detail { font-size: .88em; }
.pin-groups { margin: 0; font-weight: 650; }
.pin-groups span { color: var(--color-accent); padding: 0 8px; }
.pin-note { margin: 9px 0 0; }
.connect li { margin-bottom: 17px; }
.reset-note { background: var(--color-surface-raised); padding: 17px 21px; margin-top: 24px; box-shadow: none; border-radius: var(--radius-small); }
.reset-note h3 { margin: 0 0 10px; }
.reset-note p { margin: 7px 0 0; }

/* Signal levels and the water-cup analogy */
.page-signals main { padding: 24px 0; }
.page-signals h1 { margin-bottom: 14px; font-size: clamp(36px, 3.7vw, 58px); }
.signal-takeaway { margin: 0 0 22px; color: var(--color-accent); font-size: clamp(19px, 1.7vw, 27px); }
.signal-layout { display: grid; grid-template-columns: .9fr 1.1fr; gap: clamp(22px, 3vw, 44px); align-items: start; }
.signal-picture, .signal-explanation { min-width: 0; border: 1px solid var(--color-border); border-radius: var(--radius-panel); background: var(--color-surface); overflow: hidden; }
.signal-picture img { display: block; width: 100%; height: auto; }
.signal-picture figcaption { padding: 15px 20px; color: var(--color-muted); font-size: clamp(14px, 1.15vw, 18px); line-height: 1.5; }
.signal-explanation { padding: clamp(20px, 2vw, 30px); }
.signal-explanation h2 { font-size: clamp(23px, 2vw, 31px); margin-bottom: 14px; }
.signal-explanation ul { font-size: clamp(17px, 1.35vw, 23px); line-height: 1.4; }
.signal-explanation li { margin-bottom: 9px; }
.signal-explanation h3 { margin: 17px 0 8px; font-size: clamp(20px, 1.6vw, 26px); }
.signal-ranges { width: 100%; border-collapse: collapse; font-size: clamp(14px, 1.15vw, 19px); line-height: 1.4; }
.signal-ranges caption { color: var(--color-muted); text-align: left; padding-bottom: 8px; font-size: .9em; }
.signal-ranges th, .signal-ranges td { text-align: left; padding: 9px 7px; border-bottom: 1px solid var(--color-border); }
.signal-ranges th { color: var(--color-muted); font-weight: 600; }
.signal-ranges strong { color: var(--color-water); }
.signal-detail { color: var(--color-muted); font-size: clamp(14px, 1.15vw, 18px); margin: 10px 0 0; }
.signal-analog { margin: 0; font-size: clamp(17px, 1.4vw, 23px); }
.signal-blink { margin: 20px 0 0; padding: 17px 22px; background: var(--color-surface); border: 1px solid var(--color-border); border-radius: var(--radius-small); font-size: clamp(17px, 1.45vw, 23px); }
@media (max-width: 900px) { .signal-layout { grid-template-columns: 1fr; } .signal-picture { max-width: 675px; margin-inline: auto; } }

/* External LED lesson */
.page-external-led h1 { font-size: clamp(34px, 3.7vw, 58px); }
.page-external-led section > p { margin: 0 0 15px; font-size: clamp(18px, 1.55vw, 25px); line-height: 1.4; }
.page-external-led section > p.detail { font-size: clamp(15px, 1.2vw, 20px); color: var(--color-muted); }
.page-external-led pre { margin-bottom: 14px; padding: 16px 20px; border-radius: var(--radius-small); font-size: clamp(17px, 1.45vw, 23px); }
.led-polarity { margin: 18px 0; padding: 12px; border: 1px solid var(--color-border); border-radius: var(--radius-small); background: var(--color-code); }
.led-polarity svg { display: block; width: 100%; height: auto; max-height: 240px; }
.led-polarity figcaption { text-align: center; padding: 4px 6px 6px; font-size: clamp(15px, 1.2vw, 20px); line-height: 1.4; }
.led-polarity figcaption strong { color: var(--color-accent); }
.wiring-path { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; padding: 18px; margin-bottom: 16px; border: 1px solid var(--color-border); border-radius: var(--radius-small); background: var(--color-code); font-size: clamp(17px, 1.4vw, 23px); line-height: 1.5; }
.wiring-path b { color: var(--color-accent); }
.return-path { flex-basis: 100%; }

/* Water and circuit diagrams: preserve alignment of all layers. */
.page-diagram .slide { height: 100svh; min-height: 640px; }
.page-diagram main { min-height: 0; display: grid; grid-template-rows: auto auto minmax(0, 1fr); padding: 20px 0; }
.page-diagram h1 { font-size: clamp(32px, 3.5vw, 52px); margin-bottom: 8px; }
.page-diagram ul { font-size: clamp(18px, 1.7vw, 25px); margin: 0 0 14px; }
.page-diagram li { margin: 0; }
.page-diagram strong { color: var(--color-accent); }
.diagram { position: relative; min-height: 0; margin: 0; overflow: hidden; border-radius: var(--radius-panel); background: var(--color-surface); box-shadow: var(--shadow-panel); }
.diagram img, .diagram > svg { width: 100%; height: 100%; object-fit: contain; display: block; }
.diagram .labels, .diagram .wheel-overlay { position: absolute; inset: 0; width: 100%; height: 100%; object-fit: contain; pointer-events: none; }
.wheel-rotor { transform-origin: 803px 182px; animation: wheel-turn 3s linear infinite; }
.diagram.paused .wheel-rotor, .paused .current { animation-play-state: paused; }
.current { stroke-dasharray: 2 94; animation: circuit-flow 1s linear infinite; }
@keyframes wheel-turn { to { transform: rotate(-360deg); } }
@keyframes circuit-flow { to { stroke-dashoffset: -96; } }

/* Responsive and presentation accessibility */
@media (min-width: 1800px) {
  .slide { max-width: 1900px; margin-inline: auto; }
}
@media (max-width: 900px) {
  .comparison, .code-layout, .showcase-layout, .contact-layout { grid-template-columns: 1fr; gap: 24px; }
  .page-cover main { grid-template-columns: 1fr; gap: 28px; }
  .page-cover h1 { font-size: clamp(48px, 9vw, 76px); }
  .illustration { max-height: 350px; }
}
@media (max-width: 700px) {
  .slide { padding-top: 20px; }
  .brand { font-size: 10px; letter-spacing: .06em; }
  .brand svg { width: 26px; height: 26px; flex-shrink: 0; }
  .edition { font-size: 9px; padding: 7px 10px; text-align: center; }
  header { gap: 12px; }
  main { padding: 28px 0; }
  footer { flex-wrap: wrap; gap: 10px; font-size: 11px; }
  footer a, footer button { padding: 10px 13px; }
  .footer-right, .controls { gap: 6px; }
  .page-cover footer > span { flex-basis: 100%; }
  .page-cover .footer-right { width: 100%; justify-content: space-between; }
  .page-list main > ul { padding: 23px 22px 23px 43px; }
  .wifi { align-items: flex-start; flex-direction: column; gap: 10px; }
  .page-ide main { overflow-x: auto; }
  .ide-map { min-width: 900px; max-height: none; }
  pre { padding: 16px; }
  .finish { line-height: 1.6; }
  .page-diagram .slide { height: auto; min-height: 100svh; }
  .page-diagram main { display: flex; padding: 28px 0; }
  .diagram { margin-top: 12px; }
  .diagram > img:not(.labels), .diagram > svg:not(.labels):not(.wheel-overlay) { height: auto; }
}
@media (prefers-reduced-motion: reduce) {
  button, footer a { transition: none; }
  .wheel-rotor, .current { animation-play-state: paused; }
  .diagram.playing .wheel-rotor, .playing .current { animation-play-state: running; }
}
@media print {
  @page { size: landscape; margin: 0; }
  body { print-color-adjust: exact; -webkit-print-color-adjust: exact; }
  footer, #copy-code, #copy-status { display: none; }
}