/* ROS2Lab shared styles: notebook paper, sticker panels, node colours */
:root {
  --paper: #EAF3FF;
  --grid: #D2E2F7;
  --margin-line: #F2A2B3;
  --ink: #1D2B53;
  --ink-soft: #46557D;
  --white: #FFFFFF;
  --sun: #FFC83D;
  --sun-tint: #FFF2CC;

  --camera: #0E9F95;  --camera-tint: #D4F5F1;
  --brain: #7457EE;   --brain-tint: #EBE5FF;
  --motors: #EF7316;  --motors-tint: #FFE8D6;
  --speaker: #E2456B; --speaker-tint: #FFE2E9;
  --good: #20914A;    --good-tint: #DCF5E3;
  --bad: #C93636;     --bad-tint: #FFE3E3;

  --line: 3px solid var(--ink);
  --shadow: 6px 6px 0 var(--ink);
  --shadow-sm: 3px 3px 0 var(--ink);
  --r-panel: 28px;
  --r-card: 16px;
  --r-btn: 14px;

  --font-display: "Baloo 2", "Trebuchet MS", system-ui, sans-serif;
  --font-body: "Atkinson Hyperlegible", "Segoe UI", system-ui, sans-serif;
  --font-mono: ui-monospace, "SFMono-Regular", Menlo, Consolas, monospace;
}

*, *::before, *::after { box-sizing: border-box; }
[hidden] { display: none !important; }
[id] { scroll-margin-top: 84px; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  font-family: var(--font-body);
  font-size: 1.125rem;
  line-height: 1.6;
  color: var(--ink);
  background-color: var(--paper);
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 28px 28px;
  background-position: -1px -1px;
}
/* The red margin line of a school notebook, on wide screens only */
@media (min-width: 1000px) {
  body::before {
    content: ""; position: fixed; top: 0; bottom: 0; left: 56px;
    width: 2px; background: var(--margin-line); pointer-events: none; z-index: 0;
  }
}

img, svg { max-width: 100%; }
a { color: var(--brain); text-underline-offset: 3px; text-decoration-thickness: 2px; }
a:hover { color: var(--ink); }
:focus-visible { outline: 4px solid var(--brain); outline-offset: 3px; border-radius: 6px; }

h1, h2, h3, h4 { font-family: var(--font-display); color: var(--ink); margin: 0 0 .4em; }
h1 { font-size: clamp(2.6rem, 7vw, 4.6rem); font-weight: 800; line-height: 1; letter-spacing: -0.015em; }
h2 { font-size: clamp(1.9rem, 4.2vw, 2.7rem); font-weight: 800; line-height: 1.08; }
h3 { font-size: 1.45rem; font-weight: 700; line-height: 1.2; }
p { margin: 0 0 1em; }
.lead { font-size: clamp(1.15rem, 2.2vw, 1.35rem); color: var(--ink-soft); max-width: 46ch; }
.prose { max-width: 62ch; }
.muted { color: var(--ink-soft); }

.wrap { position: relative; z-index: 1; max-width: 1120px; margin: 0 auto; padding: 0 22px; }
.section { padding: 56px 0; }
.section-tight { padding: 28px 0; }

/* ---------- Header ---------- */
.site-header {
  position: sticky; top: 0; z-index: 50;
  background: var(--white); border-bottom: var(--line);
}
.site-header .wrap { display: flex; align-items: center; gap: 16px; min-height: 68px; }
.logo {
  display: flex; align-items: center; gap: 8px; text-decoration: none; color: var(--ink);
  font-family: var(--font-display); font-weight: 800; font-size: 1.7rem; line-height: 1;
}
.logo svg { width: 34px; height: 40px; }
.logo b { color: var(--brain); font-weight: 800; }
.nav { margin-left: auto; display: flex; align-items: center; gap: 6px; }
.nav a {
  font-family: var(--font-display); font-weight: 700; font-size: 1.08rem; color: var(--ink);
  text-decoration: none; padding: 6px 12px; border-radius: 10px;
}
.nav a:hover { background: var(--sun-tint); }
.sound-toggle {
  font-size: 1.2rem; width: 44px; height: 44px; border: var(--line); border-radius: 12px;
  background: var(--white); cursor: pointer; box-shadow: var(--shadow-sm);
}
.sound-toggle:active { transform: translate(2px, 2px); box-shadow: 1px 1px 0 var(--ink); }
@media (max-width: 640px) {
  .nav a.hide-sm { display: none; }
  .logo { font-size: 1.45rem; }
}

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: .45em;
  font-family: var(--font-display); font-weight: 700; font-size: 1.2rem; line-height: 1.1;
  padding: .75em 1.35em; color: var(--ink); text-decoration: none;
  background: var(--sun); border: var(--line); border-radius: var(--r-btn);
  box-shadow: var(--shadow-sm); cursor: pointer;
  transition: transform .08s ease, box-shadow .08s ease;
}
.btn:hover { color: var(--ink); transform: translate(-1px, -1px); box-shadow: 4px 4px 0 var(--ink); }
.btn:active { transform: translate(3px, 3px); box-shadow: 0 0 0 var(--ink); }
.btn-white { background: var(--white); }
.btn-ink { background: var(--ink); color: var(--white); }
.btn-ink:hover { color: var(--white); }
.btn[disabled], .btn[aria-disabled="true"] {
  background: #E4E8F0; color: #7A86A6; border-color: #9AA5C2; box-shadow: none; cursor: not-allowed; transform: none;
}

/* ---------- Panels and chips ---------- */
.panel {
  background: var(--white); border: var(--line); border-radius: var(--r-panel);
  box-shadow: var(--shadow); padding: clamp(20px, 4vw, 40px);
}
.chip {
  display: inline-flex; align-items: center; gap: 6px;
  font-family: var(--font-display); font-weight: 700; font-size: 1rem; line-height: 1;
  padding: 7px 14px 6px; border: 2.5px solid var(--ink); border-radius: 999px; background: var(--white);
}

/* Node colour system: every concept keeps its colour across the site */
[data-node="camera"]  { --c: var(--camera);  --t: var(--camera-tint); }
[data-node="brain"]   { --c: var(--brain);   --t: var(--brain-tint); }
[data-node="motors"]  { --c: var(--motors);  --t: var(--motors-tint); }
[data-node="speaker"] { --c: var(--speaker); --t: var(--speaker-tint); }

/* Speech bubble used by Chiku */
.bubble {
  position: relative; background: var(--white); border: var(--line); border-radius: 22px;
  padding: 14px 18px; box-shadow: var(--shadow-sm); font-size: 1.1rem;
}

/* Sequence number (only used where content is truly a sequence) */
.step-num {
  flex: none; display: inline-grid; place-items: center; width: 52px; height: 52px;
  font-family: var(--font-display); font-weight: 800; font-size: 1.6rem; line-height: 1;
  background: var(--sun); border: var(--line); border-radius: 50%; box-shadow: var(--shadow-sm);
}

/* Terminal box for real ROS 2 commands */
.terminal {
  background: var(--ink); color: #E6EEFF; border-radius: var(--r-card); border: var(--line);
  font-family: var(--font-mono); font-size: 1rem; line-height: 1.7; padding: 18px 20px; overflow-x: auto;
}
.terminal .prompt { color: var(--sun); }
.terminal .out { color: #7FF0E3; }

/* ---------- Footer ---------- */
.site-footer { border-top: var(--line); background: var(--white); margin-top: 40px; }
.site-footer .wrap { padding-top: 28px; padding-bottom: 36px; display: grid; gap: 10px; }
.site-footer p { margin: 0; font-size: 1rem; color: var(--ink-soft); }
.site-footer .logo { font-size: 1.4rem; }

/* ---------- Motion ---------- */
@keyframes shake { 0%,100% { transform: translateX(0); } 20% { transform: translateX(-8px); } 40% { transform: translateX(7px); } 60% { transform: translateX(-5px); } 80% { transform: translateX(3px); } }
@keyframes pop { 0% { transform: scale(.6); opacity: 0; } 70% { transform: scale(1.08); opacity: 1; } 100% { transform: scale(1); opacity: 1; } }
@keyframes fall { to { transform: translate(var(--dx), 340px) rotate(var(--rot)); opacity: 0; } }
.confetti {
  position: absolute; top: 10px; width: 10px; height: 14px; z-index: 5;
  border: 2px solid var(--ink); border-radius: 3px; pointer-events: none;
  animation: fall 1.6s ease-in forwards;
}
.shake { animation: shake .45s ease; }
.pop { animation: pop .4s ease both; }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: .01ms !important; animation-iteration-count: 1 !important;
    transition-duration: .01ms !important; scroll-behavior: auto !important;
  }
}

.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }