:root {
  --ink: #000;
  --paper: #fff;
  --sans: "Figtree", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
    Helvetica, Arial, sans-serif;
}

:root[data-theme="dark"] {
  --ink: #fff;
  --paper: #000;
}

:root[data-theme="light"] {
  --ink: #000;
  --paper: #fff;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --ink: #fff;
    --paper: #000;
  }
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  font-size: clamp(16px, 0.3vw + 15px, 18px);
  font-weight: 400;
  line-height: 1.65;
  letter-spacing: -0.01em;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Centred column, left-aligned text */
main {
  max-width: 720px;
  margin-inline: auto;
  padding-inline: 24px;
  padding-block: clamp(80px, 16vh, 200px) clamp(64px, 10vh, 120px);
}

.mark {
  font-size: clamp(48px, 6vw, 64px);
  line-height: 1;
  margin: 0 0 clamp(40px, 6vh, 72px);
}

p { margin: 0 0 1.5em; }

p:last-child { margin-bottom: 0; }

a {
  color: inherit;
  text-decoration: underline;
  text-underline-offset: 3px;
  text-decoration-thickness: 1px;
}

a:hover { text-decoration-thickness: 2px; }

a:focus-visible {
  outline: 2px solid var(--ink);
  outline-offset: 3px;
  border-radius: 2px;
}

/* Emoji links: no underline, opacity instead of a decoration change.
   app.js adds .plain to any link whose text is emoji only. */
a.plain,
.back a {
  text-decoration: none;
  transition: opacity 0.15s ease;
}

a.plain:hover,
.back a:hover {
  text-decoration: none;
  opacity: 0.6;
}

.page h2 {
  font-size: 1em;
  font-weight: 600;
  margin: 2.4em 0 0.8em;
}

.back { margin-top: 3em; }

/* Pill toggle, top right */
.theme {
  position: fixed;
  top: clamp(16px, 2.6vh, 28px);
  right: clamp(16px, 2.6vw, 28px);
  z-index: 10;
  display: inline-flex;
  align-items: center;
  width: 52px;
  height: 28px;
  padding: 3px;
  appearance: none;
  border: 1px solid color-mix(in srgb, currentColor 22%, transparent);
  border-radius: 999px;
  background: none;
  color: inherit;
  cursor: pointer;
  transition: border-color 0.2s ease;
}

.theme:hover {
  border-color: color-mix(in srgb, currentColor 45%, transparent);
}

.theme:focus-visible {
  outline: 2px solid var(--ink);
  outline-offset: 3px;
}

.knob {
  display: grid;
  place-items: center;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--ink);
  color: var(--paper);
  transform: translateX(0);
  transition: transform 0.22s cubic-bezier(0.2, 0, 0, 1);
}

.knob svg {
  width: 12px;
  height: 12px;
  display: block;
}

.icon-sun { display: block; }
.icon-moon { display: none; }

/* Dark: knob slides right, moon shows */
:root[data-theme="dark"] .knob { transform: translateX(22px); }
:root[data-theme="dark"] .icon-sun { display: none; }
:root[data-theme="dark"] .icon-moon { display: block; }

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .knob { transform: translateX(22px); }
  :root:not([data-theme="light"]) .icon-sun { display: none; }
  :root:not([data-theme="light"]) .icon-moon { display: block; }
}

:root[data-theme="light"] .knob { transform: translateX(0); }
:root[data-theme="light"] .icon-sun { display: block; }
:root[data-theme="light"] .icon-moon { display: none; }

@media (prefers-reduced-motion: reduce) {
  * { transition: none !important; animation: none !important; }
}