:root{
  /* Shared motion/timing across ALL elements */
  --reveal-dur: 520ms;
  --reveal-ease: cubic-bezier(.2,.8,.2,1);

  /* Approx logo-family light blue (tweak if you want) */
  --brand-sky: #74BCEB;

  /* LIGHT THEME (default) */
  --bg: #F7FBFF;
  --text: rgba(10, 18, 35, .92);
  --muted: rgba(10, 18, 35, .62);

  --cardA: rgba(116, 188, 235, .18);
  --cardA-border: rgba(20, 70, 140, .14);

  --cardB: rgba(20, 70, 140, .10);
  --cardB-border: rgba(20, 70, 140, .14);

  --side: rgba(20, 70, 140, .06);
  --side-border: rgba(20, 70, 140, .10);

  /* Side quest panel should read clearly */
  --sq-panel: rgba(255,255,255,.92);
  --sq-panel-border: rgba(20,70,140,.14);

  --accent: rgba(20, 70, 140, .92);
  --accent2: rgba(0, 170, 140, .90);

  --timeline-line: rgba(116, 188, 235, .95);

  --radius: 18px;
  --shadow: 0 12px 40px rgba(0,0,0,.18);
  --topbar-h: 54px;

  /* Header geometry */
  --section-header-pad-top: 24px; /* ↑ moved down so it doesn't collide with topbar/title */
  --section-header-gap: 10px;

  /* Nudge position so it won't cover the "peek" */
  --nudge-bottom: 78px;
}

/* DARK THEME overrides (current look) */
html[data-theme="dark"]{
  --bg: #070A12;
  --text: rgba(255,255,255,.92);
  --muted: rgba(255,255,255,.68);

  --cardA: rgba(150, 190, 255, .14);
  --cardA-border: rgba(150, 190, 255, .20);

  --cardB: rgba(210, 220, 235, .20);
  --cardB-border: rgba(210, 220, 235, .26);

  --side: rgba(255,255,255,.06);
  --side-border: rgba(255,255,255,.10);

  /* Brighter panel on dark background */
  --sq-panel: rgba(18, 24, 40, .92);
  --sq-panel-border: rgba(150, 190, 255, .22);

  --accent: rgba(140, 190, 255, .95);
  --accent2: rgba(120, 255, 210, .90);

  --timeline-line: rgba(116, 188, 235, .92);

  --shadow: 0 12px 40px rgba(0,0,0,.35);
}

*{ box-sizing: border-box; }
html, body { height: 100%; }

body{
  margin: 0;
  color: var(--text);
  font-family: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, "Apple Color Emoji", "Segoe UI Emoji";
  overflow: hidden; /* snap-root handles scrolling */
}

/* Backgrounds */
html[data-theme="light"] body{
  background:
    radial-gradient(1100px 760px at 70% 10%, rgba(116,188,235,.22), transparent 56%),
    radial-gradient(900px 680px at 22% 82%, rgba(0,170,140,.12), transparent 62%),
    radial-gradient(700px 520px at 10% 18%, rgba(20,70,140,.08), transparent 60%),
    var(--bg);
}

html[data-theme="dark"] body{
  background:
    radial-gradient(1200px 800px at 70% 10%, rgba(140,190,255,.14), transparent 55%),
    radial-gradient(900px 700px at 20% 80%, rgba(120,255,210,.10), transparent 60%),
    var(--bg);
}

/* Top bar */
.topbar{
  position: fixed;
  top: 0;
  left: 0; right: 0;
  height: var(--topbar-h);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 14px;
  z-index: 80;
  background: linear-gradient(to bottom, rgba(0,0,0,.08), rgba(0,0,0,0));
  pointer-events: none;
}

.brand{
  pointer-events: auto;
  text-decoration: none;
  color: var(--text);
  font-weight: 700;
  letter-spacing: .2px;
  opacity: .92;
}

.topbar-right{ pointer-events: auto; }

/* Theme toggle */
.theme-toggle{
  display: flex;
  align-items: center;
  gap: 10px;
  pointer-events: auto;
}
.theme-toggle__label{
  font-size: 12px;
  color: var(--muted);
  letter-spacing: .08em;
  text-transform: uppercase;
}

/* Switch */
.switch{
  position: relative;
  width: 46px;
  height: 26px;
  display: inline-block;
}
.switch input{
  position: absolute;
  opacity: 0;
  inset: 0;
}
.switch__track{
  position: absolute;
  inset: 0;
  border-radius: 999px;
  background: rgba(255,255,255,.10);
  border: 1px solid rgba(255,255,255,.14);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
}
html[data-theme="light"] .switch__track{
  background: rgba(20,70,140,.08);
  border-color: rgba(20,70,140,.16);
}
.switch__thumb{
  position: absolute;
  top: 3px;
  left: 3px;
  width: 20px;
  height: 20px;
  border-radius: 999px;
  background: rgba(255,255,255,.90);
  transition: transform 220ms var(--reveal-ease);
}
html[data-theme="light"] .switch__thumb{
  background: rgba(20,70,140,.78);
}
.switch input:checked ~ .switch__thumb{
  transform: translateX(20px);
}

/* Scroll snap root */
.snap-root{
  height: 100vh;
  overflow-y: auto;
  overscroll-behavior-y: contain;
  scroll-snap-type: y mandatory;
  scroll-behavior: smooth;
  -webkit-overflow-scrolling: touch;
  padding-top: var(--topbar-h);
}

/* Sections */
.section{
  position: relative;
  scroll-snap-align: start;
  min-height: calc(100vh - var(--topbar-h));
  padding: 16px 16px 26px;
  display: grid;
  grid-template-rows: auto 1fr;
  gap: 10px;
  align-content: start;
}

/* HEADER */
.section__header{
  position: relative;
  z-index: 20; /* above the center line */
  padding-top: var(--section-header-pad-top);
  display: grid;
  gap: 6px;
  width: min(980px, 100%);
  margin: 0 auto;
}

.section__kicker{
  font-size: 12px;
  letter-spacing: .16em;
  text-transform: uppercase;
  color: var(--muted);
  opacity: .85;
}

.section__title{
  font-size: 26px;
  font-weight: 900;
  letter-spacing: .2px;
  line-height: 1.05;
}

/* Timeline label under title */
.timeline-label{
  justify-self: center;
  display: inline-grid;
  justify-items: center;
  gap: 8px;
  margin-top: 8px;
}

.timeline-label__dot{
  width: 16px;
  height: 16px;
  border-radius: 999px;
  border: 3px solid color-mix(in srgb, var(--timeline-line) 78%, white 0%);
  background: color-mix(in srgb, var(--bg) 82%, transparent);
  box-shadow: 0 0 0 10px color-mix(in srgb, var(--timeline-line) 10%, transparent);
}

.timeline-label__pill{
  font-size: 12px;
  color: var(--text);
  padding: 6px 10px;
  border-radius: 999px;
  border: 1px solid rgba(255,255,255,.10);
  background: rgba(0,0,0,.18);
  white-space: nowrap;
  box-shadow: var(--shadow);
}

html[data-theme="light"] .timeline-label__pill{
  border-color: rgba(20,70,140,.14);
  background: rgba(255,255,255,.72);
}

/* BODY centers content */
.section__body{
  position: relative;
  z-index: 15;
  display: grid;
  place-items: center;
  padding-top: 4px;
}

.section__grid{
  display: grid;
  grid-template-columns: 1fr;
  gap: 14px;
  width: min(740px, 100%);
  margin: 0 auto;
}

@media (min-width: 860px){
  .section{
    padding: 18px 22px 30px;
  }
  .section__grid{
    width: min(980px, 100%);
    grid-template-columns: 1.1fr .9fr;
    align-items: start;
    gap: 18px;
  }
}

/* Reveal */
.reveal{
  opacity: 0;
  transform: translateY(12px);
  filter: blur(6px);
  transition:
    opacity var(--reveal-dur) var(--reveal-ease),
    transform var(--reveal-dur) var(--reveal-ease),
    filter var(--reveal-dur) var(--reveal-ease);
  will-change: opacity, transform, filter;
}
.reveal.in{
  opacity: 1;
  transform: translateY(0);
  filter: blur(0);
}

/* Cards */
.card{
  position: relative;
  z-index: 10;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  border: 1px solid transparent;
  padding: 16px 16px;
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
}

.cardA{
  background: var(--cardA);
  border-color: var(--cardA-border);
}
.cardA h2{
  margin: 0 0 10px;
  font-size: 20px;
  letter-spacing: .2px;
}
.cardA p{
  margin: 0;
  line-height: 1.45;
  color: color-mix(in srgb, var(--text) 92%, transparent);
}

/* Inline code */
.richtext code{
  padding: 1px 6px;
  border-radius: 8px;
  border: 1px solid rgba(255,255,255,.10);
  background: rgba(0,0,0,.14);
  color: var(--text);
}
html[data-theme="light"] .richtext code{
  border-color: rgba(20,70,140,.14);
  background: rgba(20,70,140,.06);
}

/* Terms */
.term{
  color: var(--accent);
  font-weight: 700;
  text-decoration: underline;
  text-decoration-color: color-mix(in srgb, var(--accent) 35%, transparent);
  text-underline-offset: 3px;
  cursor: pointer;
}

/* Element C */
.cardSide{
  background: var(--side);
  border-color: var(--side-border);
  overflow: hidden;
}
.side-media{
  width: 100%;
  height: 220px;
  border-radius: 14px;
  border: 1px solid rgba(255,255,255,.10);
  background: rgba(255,255,255,.05);
  display: grid;
  place-items: center;
  color: color-mix(in srgb, var(--text) 70%, transparent);
  font-size: 13px;
}
html[data-theme="light"] .side-media{
  border-color: rgba(20,70,140,.12);
  background: rgba(20,70,140,.05);
}
@media (min-width: 860px){
  .side-media{ height: 320px; }
}

.delay-1s{
  transition-delay: 1s;
}

/* Center timeline line */
.timeline-center{
  position: fixed;
  top: var(--topbar-h);
  bottom: 0;
  left: 50%;
  width: 64px;
  transform: translateX(-50%);
  z-index: 4;
  pointer-events: none;
}
.timeline-center__line{
  position: absolute;
  top: 16px;
  bottom: 16px;
  left: 50%;
  width: 8px;
  transform: translateX(-50%);
  border-radius: 999px;
  background:
    linear-gradient(to bottom,
      color-mix(in srgb, var(--timeline-line) 0%, transparent),
      color-mix(in srgb, var(--timeline-line) 75%, transparent),
      color-mix(in srgb, var(--timeline-line) 0%, transparent)
    );
  box-shadow: 0 0 0 6px color-mix(in srgb, var(--timeline-line) 10%, transparent);
  opacity: .95;
}

/* (2) Mobile-only dim so it doesn't glow through cards */
@media (max-width: 859px){
  .timeline-center__line{
    opacity: .55;
    box-shadow: 0 0 0 4px color-mix(in srgb, var(--timeline-line) 8%, transparent);
  }
}

/* Definition popover */
.def-popover{
  position: fixed;
  z-index: 90;
  width: min(320px, calc(100vw - 22px));
  background: var(--cardB);
  border: 1px solid var(--cardB-border);
  border-radius: 16px;
  box-shadow: var(--shadow);
  padding: 12px 12px;
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);

  opacity: 0;
  transform: translateY(10px);
  pointer-events: none;
  transition: opacity var(--reveal-dur) var(--reveal-ease), transform var(--reveal-dur) var(--reveal-ease);
}
.def-popover.open{
  opacity: 1;
  transform: translateY(0);
  pointer-events: auto;
}
.def-popover__header{
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  margin-bottom: 8px;
}
.def-popover__title{
  font-weight: 800;
  font-size: 14px;
  color: var(--text);
}
.def-popover__body{
  font-size: 14px;
  line-height: 1.45;
  color: color-mix(in srgb, var(--text) 86%, transparent);
}
.icon-btn{
  border: 0;
  width: 34px; height: 34px;
  border-radius: 10px;
  background: rgba(255,255,255,.08);
  color: var(--text);
}
html[data-theme="light"] .icon-btn{
  background: rgba(20,70,140,.08);
}

/* Side quest */
.sidequest{
  position: fixed;
  inset: 0;
  z-index: 120;
  background: rgba(0,0,0,.55);
  backdrop-filter: blur(6px);
  -webkit-backdrop-filter: blur(6px);

  opacity: 0;
  pointer-events: none;
  transition: opacity var(--reveal-dur) var(--reveal-ease);
}
html[data-theme="light"] .sidequest{
  background: rgba(10,18,35,.35);
}
.sidequest.open{
  opacity: 1;
  pointer-events: auto;
}

.sidequest__panel{
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
  width: min(760px, calc(100vw - 22px));
  height: min(78vh, 620px);

  background: var(--sq-panel);
  border: 1px solid var(--sq-panel-border);
  border-radius: 22px;
  box-shadow: var(--shadow);
  overflow: hidden;

  display: grid;
  grid-template-rows: 1fr auto;
}

.sidequest__content{
  padding: 16px 16px 12px;
  overflow: auto;
  -webkit-overflow-scrolling: touch;
}
.sidequest__title{
  font-size: 18px;
  font-weight: 900;
  margin: 0 0 10px;
  color: var(--text);
}
.sidequest__body{
  color: color-mix(in srgb, var(--text) 90%, transparent);
  line-height: 1.5;
}
.sidequest__close{
  border: 0;
  padding: 14px 16px;
  background: color-mix(in srgb, var(--brand-sky) 22%, transparent);
  color: var(--text);
  font-weight: 900;
  letter-spacing: .08em;
}

/* Scroll nudge */
.scroll-nudge{
  position: fixed;
  left: 50%;
  bottom: var(--nudge-bottom);
  transform: translateX(-50%);
  z-index: 95;
  pointer-events: none;

  opacity: 0;
  transition: opacity var(--reveal-dur) var(--reveal-ease);
}
.scroll-nudge.show{ opacity: 1; }

.scroll-nudge__inner{
  display: grid;
  justify-items: center;
  gap: 2px;
  padding: 10px 14px 9px;
  border-radius: 999px;
  border: 1px solid rgba(255,255,255,.12);
  background: rgba(0,0,0,.22);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  box-shadow: var(--shadow);
}
html[data-theme="light"] .scroll-nudge__inner{
  border-color: rgba(20,70,140,.14);
  background: rgba(255,255,255,.68);
}

.scroll-nudge__chev{
  font-size: 18px;
  line-height: 12px;
  color: color-mix(in srgb, var(--text) 86%, transparent);
  animation: nudgeBounce 1.15s var(--reveal-ease) infinite;
}
.scroll-nudge__chev:nth-child(2){
  animation-delay: 120ms;
  opacity: .75;
}
.scroll-nudge__label{
  margin-top: 2px;
  font-size: 12px;
  letter-spacing: .12em;
  text-transform: uppercase;
  color: color-mix(in srgb, var(--text) 70%, transparent);
}

@keyframes nudgeBounce{
  0%, 100% { transform: translateY(0); opacity: .72; }
  50%      { transform: translateY(5px); opacity: 1; }
}

/* Reduced motion */
@media (prefers-reduced-motion: reduce){
  .snap-root{ scroll-behavior: auto; }
  .reveal, .def-popover, .sidequest{
    transition: none !important;
    transform: none !important;
    filter: none !important;
  }
  .scroll-nudge__chev{ animation: none !important; }
}