/* ==========================================================================
   How the Internet Works — page styles
   A sunny, low-poly, theme-park flavoured layout.
   ========================================================================== */

:root {
  --grass:      #6fae52;
  --grass-dk:   #4f8a3a;
  --sky:        #bfe6f5;
  --sea:        #2f9bc7;
  --sand:       #e8d6a8;
  --ink:        #16232c;
  --ink-soft:   #46606f;
  --paper:      #fbf7ec;
  --paper-2:    #f2ebd9;
  --line:       #ddd2b6;
  --accent:     #e8663c;
  --accent-2:   #f2a93b;
  --violet:     #7a5cc4;
  --cyan:       #2fb3c9;
  --shadow:     0 2px 0 rgba(22, 35, 44, .18), 0 12px 28px rgba(22, 35, 44, .10);
  --radius:     14px;
  --maxw:       960px;
  --mono: ui-monospace, "SF Mono", "SFMono-Regular", Menlo, Consolas, monospace;
  --sans: "Trebuchet MS", "Segoe UI", system-ui, -apple-system, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --sky:      #16323f;
    --ink:      #ecf3f6;
    --ink-soft: #a8c0cc;
    --paper:    #12222b;
    --paper-2:  #172c37;
    --line:     #2b4553;
    --shadow:   0 2px 0 rgba(0, 0, 0, .35), 0 12px 28px rgba(0, 0, 0, .35);
  }
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }

body {
  margin: 0;
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.65;
  color: var(--ink);
  background: var(--paper);
  -webkit-text-size-adjust: 100%;
}

.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 20px; }

a { color: var(--accent); text-decoration-thickness: 2px; text-underline-offset: 2px; }
a:hover { color: var(--accent-2); }

code, kbd {
  font-family: var(--mono);
  font-size: .88em;
  background: var(--paper-2);
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: .08em .38em;
}

/* --------------------------------------------------------------- header  */

.hero {
  position: relative;
  overflow: hidden;
  background: linear-gradient(180deg, var(--sky) 0%, var(--paper) 100%);
  padding: 54px 0 34px;
  border-bottom: 3px solid var(--line);
}

.hero h1 {
  margin: 0 0 10px;
  font-size: clamp(32px, 6vw, 54px);
  line-height: 1.05;
  letter-spacing: -.02em;
  text-shadow: 0 2px 0 rgba(255, 255, 255, .5);
}

@media (prefers-color-scheme: dark) {
  .hero h1 { text-shadow: 0 2px 0 rgba(0, 0, 0, .35); }
}

.hero p.lede {
  margin: 0;
  max-width: 62ch;
  font-size: clamp(17px, 2.3vw, 21px);
  color: var(--ink-soft);
}

.eyebrow {
  display: inline-block;
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: .16em;
  text-transform: uppercase;
  color: var(--ink-soft);
  border: 1px solid var(--line);
  background: var(--paper);
  border-radius: 999px;
  padding: 4px 12px;
  margin-bottom: 16px;
}

/* ------------------------------------------------------------ simulator  */

.sim-shell {
  margin: 26px 0 8px;
  background: var(--paper-2);
  border: 2px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  overflow: hidden;
}

.sim-topbar {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
  padding: 10px 12px;
  border-bottom: 2px solid var(--line);
  background: linear-gradient(180deg, rgba(255, 255, 255, .35), transparent);
}

.sim-title {
  font-weight: 700;
  font-size: 14px;
  letter-spacing: .04em;
  text-transform: uppercase;
  margin-right: auto;
  color: var(--ink-soft);
}

button.btn {
  font-family: var(--sans);
  font-size: 14px;
  font-weight: 700;
  color: var(--ink);
  background: var(--paper);
  border: 2px solid var(--line);
  border-bottom-width: 3px;
  border-radius: 10px;
  padding: 6px 12px;
  cursor: pointer;
  transition: transform .08s ease, background .15s ease;
}
button.btn:hover { background: #fff2; border-color: var(--ink-soft); }
button.btn:active { transform: translateY(2px); border-bottom-width: 2px; }
button.btn[aria-pressed="true"], button.btn.is-on {
  background: var(--accent);
  border-color: #b44e2c;
  color: #fff;
}
button.btn:focus-visible, select:focus-visible, input:focus-visible, a:focus-visible {
  outline: 3px solid var(--violet);
  outline-offset: 2px;
}

.icon-btn { min-width: 38px; text-align: center; }

.stage {
  position: relative;
  background: linear-gradient(180deg, #cfeaf6 0%, #bfe6f5 55%, #a9dcef 100%);
  touch-action: none;
}
@media (prefers-color-scheme: dark) {
  .stage { background: linear-gradient(180deg, #143543 0%, #123040 55%, #0e2735 100%); }
}

.stage canvas { display: block; width: 100%; height: auto; cursor: grab; }
.stage canvas.dragging { cursor: grabbing; }

.hud {
  position: absolute;
  top: 10px; left: 10px;
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  pointer-events: none;
}

.chip {
  font-family: var(--mono);
  font-size: 12px;
  background: rgba(18, 34, 43, .78);
  color: #eaf6fb;
  border-radius: 8px;
  padding: 4px 9px;
  white-space: nowrap;
}
.chip b { color: var(--accent-2); font-weight: 700; }

.narrator {
  display: flex;
  gap: 12px;
  align-items: flex-start;
  padding: 12px 14px;
  border-top: 2px solid var(--line);
  background: var(--paper);
  min-height: 74px;
}
.narrator .step-no {
  flex: none;
  width: 30px; height: 30px;
  border-radius: 8px;
  display: grid; place-items: center;
  background: var(--accent);
  color: #fff;
  font-weight: 700;
  font-family: var(--mono);
  font-size: 14px;
}
.narrator .step-text { margin: 0; }
.narrator .step-text strong { display: block; }
.narrator .step-text span { color: var(--ink-soft); font-size: 15.5px; }

.sim-bottombar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px 14px;
  padding: 10px 12px;
  border-top: 2px solid var(--line);
  font-size: 13px;
}
.sim-bottombar label { display: inline-flex; align-items: center; gap: 7px; color: var(--ink-soft); font-weight: 700; }
input[type="range"] { accent-color: var(--accent); width: 120px; }

.legend { display: flex; flex-wrap: wrap; gap: 6px 14px; margin-left: auto; }
.legend span { display: inline-flex; align-items: center; gap: 6px; color: var(--ink-soft); }
.legend i {
  width: 11px; height: 11px;
  border-radius: 3px;
  display: inline-block;
  transform: rotate(45deg);
  border: 1px solid rgba(0, 0, 0, .25);
}

.sim-note { font-size: 13.5px; color: var(--ink-soft); margin: 10px 0 0; }

/* ------------------------------------------------------------- sections  */

main section { padding: 30px 0 6px; }

h2 {
  font-size: clamp(24px, 3.6vw, 32px);
  line-height: 1.15;
  margin: 26px 0 6px;
  letter-spacing: -.01em;
}
h2 .num {
  font-family: var(--mono);
  font-size: .6em;
  color: var(--accent);
  margin-right: .5em;
}
h3 { font-size: 20px; margin: 24px 0 4px; }

p { margin: 12px 0; }
p.sub { color: var(--ink-soft); margin-top: 0; }

ul, ol { padding-left: 22px; }
li { margin: 6px 0; }

.card {
  background: var(--paper-2);
  border: 2px solid var(--line);
  border-left-width: 6px;
  border-left-color: var(--cyan);
  border-radius: 12px;
  padding: 14px 16px;
  margin: 18px 0;
}
.card h4 { margin: 0 0 6px; font-size: 15px; text-transform: uppercase; letter-spacing: .06em; color: var(--ink-soft); }
.card p:last-child { margin-bottom: 0; }
.card.warn { border-left-color: var(--accent-2); }
.card.green { border-left-color: var(--grass-dk); }

.grid2 { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 14px; margin: 18px 0; }

.tile {
  background: var(--paper-2);
  border: 2px solid var(--line);
  border-radius: 12px;
  padding: 12px 14px;
}
.tile h4 { margin: 0 0 4px; font-size: 16px; }
.tile p { margin: 0; font-size: 15px; color: var(--ink-soft); }

table { width: 100%; border-collapse: collapse; margin: 18px 0; font-size: 15px; }
th, td { text-align: left; padding: 9px 10px; border-bottom: 1px solid var(--line); vertical-align: top; }
th { background: var(--paper-2); font-size: 13px; text-transform: uppercase; letter-spacing: .05em; color: var(--ink-soft); }
.table-scroll { overflow-x: auto; }

.trace {
  font-family: var(--mono);
  font-size: 13.5px;
  line-height: 1.6;
  background: #12222b;
  color: #d7e8ef;
  border-radius: 12px;
  padding: 14px 16px;
  overflow-x: auto;
  border: 2px solid #0b171e;
}
.trace .c { color: #7fa7b6; }
.trace .k { color: #f2a93b; }
.trace .g { color: #8fd06a; }

/* jump nav */
.toc {
  position: sticky;
  top: 0;
  z-index: 5;
  background: color-mix(in srgb, var(--paper) 92%, transparent);
  backdrop-filter: blur(6px);
  border-bottom: 2px solid var(--line);
  margin-bottom: 6px;
}
.toc ul {
  display: flex;
  gap: 4px;
  overflow-x: auto;
  list-style: none;
  margin: 0;
  padding: 8px 20px;
  max-width: var(--maxw);
  margin-inline: auto;
  scrollbar-width: thin;
}
.toc a {
  white-space: nowrap;
  font-size: 13px;
  font-weight: 700;
  text-decoration: none;
  color: var(--ink-soft);
  border: 1px solid transparent;
  border-radius: 999px;
  padding: 4px 10px;
}
.toc a:hover { background: var(--paper-2); border-color: var(--line); color: var(--ink); }

footer {
  margin-top: 40px;
  padding: 26px 0 44px;
  border-top: 3px solid var(--line);
  background: var(--paper-2);
  color: var(--ink-soft);
  font-size: 15px;
}
footer a { color: var(--ink); }

@media (max-width: 620px) {
  body { font-size: 16px; }
  .legend { width: 100%; margin-left: 0; }
  .sim-title { width: 100%; margin-bottom: 4px; }
}