/* Universe Scroller — mobile-first.
   Most visitors arrive on a phone, so the small-screen layout is the base and
   desktop is the enhancement. */

:root {
  --bg:    #04060c;
  --ink:   #eaf2ff;
  --accent:#9fc0ff;
  --dim:   rgba(159,192,255,.55);
  --pad:   18px;
  --safe-l: max(var(--pad), env(safe-area-inset-left));
  --safe-r: max(var(--pad), env(safe-area-inset-right));
  --safe-b: max(14px, env(safe-area-inset-bottom));
  --safe-t: max(12px, env(safe-area-inset-top));
  --mono: ui-monospace, 'SF Mono', 'Consolas', 'Roboto Mono', monospace;
}

* { margin: 0; padding: 0; box-sizing: border-box; }
html {
  scrollbar-width: thin; scrollbar-color: #2a3a55 #04060c;
  /* kill pull-to-refresh + rubber-band chaining: on a scroll-driven page a
     stray overscroll at the top would otherwise reload the whole journey */
  overscroll-behavior-y: none;
  overflow-x: hidden;          /* nothing here ever scrolls sideways */
}
body {
  background: var(--bg); color: var(--ink); font-family: var(--mono);
  overscroll-behavior-y: none;
  -webkit-tap-highlight-color: transparent;
}

#spacer { width: 100%; }

/* Fixed full-bleed layers. 100lvh (largest viewport) rather than 100vh/dvh so
   the canvas never resizes when a mobile browser collapses its URL bar — that
   resize used to reseed the starfield mid-scroll. */
#view, #fx-stars, #fx-micro {
  position: fixed; inset: 0; width: 100vw; display: block;
  height: 100vh; height: 100lvh;
}
#view { will-change: filter; }

#fx-stars, #fx-micro {
  z-index: 1; pointer-events: none; opacity: 0; mix-blend-mode: screen;
}
/* dropped out of the compositor entirely when invisible (mobile paint cost) */
#fx-stars.off, #fx-micro.off { display: none; }

/* film grain: unifies the AI-video look and hides compression edges */
#grain {
  position: fixed; inset: -30%; z-index: 2; pointer-events: none;
  opacity: .05; mix-blend-mode: soft-light;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='140' height='140'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.85' numOctaves='2' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
  animation: grainshift 1.1s steps(3) infinite;
}
@keyframes grainshift {
  0%   { transform: translate(0,0); }
  33%  { transform: translate(-2%, 1.5%); }
  66%  { transform: translate(1.5%, -2%); }
  100% { transform: translate(0,0); }
}

/* vignette + scrims that keep the UI legible over any frame */
#vignette {
  position: fixed; inset: 0; z-index: 2; pointer-events: none;
  background:
    linear-gradient(to bottom, rgba(4,6,12,.60) 0%, rgba(4,6,12,0) 18%),
    linear-gradient(to top,    rgba(4,6,12,.78) 0%, rgba(4,6,12,.28) 18%, rgba(4,6,12,0) 38%),
    radial-gradient(140% 100% at 50% 44%, rgba(4,6,12,0) 46%, rgba(4,6,12,.30) 80%, rgba(4,6,12,.66) 100%);
}

/* ---------------------------------------------------------------- topbar */
.topbar {
  position: fixed; z-index: 4;
  top: var(--safe-t); left: var(--safe-l); right: var(--safe-r);
  display: flex; align-items: center; justify-content: space-between; gap: 12px;
  pointer-events: none;
}
.topbar .back {
  display: inline-flex; align-items: center; gap: 6px;
  /* 44px tall touch target without visually bulking the chrome */
  margin: -12px 0 -12px -10px; padding: 12px 10px;
  color: var(--accent); text-decoration: none; pointer-events: auto;
  font-size: 11px; letter-spacing: .18em; text-transform: uppercase;
  opacity: .78; transition: opacity .25s;
  text-shadow: 0 1px 6px rgba(0,0,0,.9);
}
.topbar .back svg {
  width: 15px; height: 15px; fill: none; stroke: currentColor;
  stroke-width: 2; stroke-linecap: round; stroke-linejoin: round;
}
.topbar .back:active { opacity: 1; }
.topbar .title {
  font-size: 10px; letter-spacing: .34em; text-transform: uppercase;
  color: var(--accent); opacity: .5; text-shadow: 0 1px 6px rgba(0,0,0,.9);
  white-space: nowrap;
}

/* ------------------------------------------------------------ chapter rail */
.rail {
  position: fixed; z-index: 4; right: 0; top: 50%; transform: translateY(-50%);
  display: flex; flex-direction: column; align-items: flex-end;
  padding-right: max(6px, env(safe-area-inset-right));
}
.rail .tick {
  -webkit-appearance: none; appearance: none; background: none; border: 0;
  display: flex; align-items: center; justify-content: flex-end;
  /* small marks, generous invisible hit area */
  width: 40px; height: 26px; padding: 0 6px 0 0; cursor: pointer;
  pointer-events: auto;
}
.rail .tick i {
  display: block; width: 9px; height: 2px; border-radius: 2px;
  background: var(--accent); opacity: .3;
  transition: width .3s cubic-bezier(.2,.7,.3,1), opacity .3s;
}
.rail .tick.done i { opacity: .5; }
.rail .tick.on i {
  width: 22px; opacity: 1;
  box-shadow: 0 0 10px rgba(159,192,255,.75);
}

/* -------------------------------------------------------------------- HUD */
.hud {
  position: fixed; z-index: 4;
  left: var(--safe-l); right: 64px; bottom: calc(var(--safe-b) + 20px);
  color: var(--accent); user-select: none; pointer-events: none;
  text-shadow: 0 1px 10px rgba(0,0,0,.95);
}
.hud .label {
  font-size: 10px; letter-spacing: .3em; text-transform: uppercase;
  opacity: .8; margin-bottom: 7px;
}
.hud .alt {
  font-size: 30px; line-height: 1.05; font-weight: 700; letter-spacing: -.01em;
  color: var(--ink); font-variant-numeric: tabular-nums;
  text-shadow: 0 1px 10px rgba(0,0,0,.95), 0 0 24px rgba(159,192,255,.24);
}
.hud .exp {
  font-size: 11px; letter-spacing: .12em; opacity: .62; margin-top: 5px;
}
.hud .exp sup { font-size: .74em; }

/* progress hairline, pinned to the very bottom edge */
.progress {
  position: fixed; z-index: 4; left: 0; right: 0; bottom: 0;
  height: 2px; background: rgba(159,192,255,.14); pointer-events: none;
}
.progress i {
  display: block; height: 100%; width: 0;
  background: linear-gradient(90deg, #6f97e6, #9fc0ff 55%, #d8e6ff);
  box-shadow: 0 0 10px rgba(159,192,255,.6);
}

/* ------------------------------------------------------------------- hint */
.hint {
  position: fixed; z-index: 4; left: 50%; transform: translateX(-50%);
  bottom: calc(var(--safe-b) + 20px);
  display: flex; flex-direction: column; align-items: center; gap: 8px;
  color: var(--ink); font-size: 10px; letter-spacing: .28em; text-transform: uppercase;
  opacity: .75; transition: opacity .5s; pointer-events: none;
  text-shadow: 0 1px 8px rgba(0,0,0,.9); white-space: nowrap;
}
.hint.gone { opacity: 0; }
.hint b {
  width: 16px; height: 16px; border-right: 1.5px solid currentColor;
  border-bottom: 1.5px solid currentColor; transform: rotate(45deg);
  animation: bob 1.8s ease-in-out infinite; opacity: .8;
}
@keyframes bob {
  0%,100% { transform: rotate(45deg) translate(0,0); }
  50%     { transform: rotate(45deg) translate(3px,3px); }
}
/* on phones the hint sits above the readout instead of beside it */
.hint { bottom: calc(var(--safe-b) + 118px); }

/* ----------------------------------------------------------------- loader */
#loader {
  position: fixed; inset: 0; z-index: 6; display: flex; flex-direction: column;
  align-items: center; justify-content: center; gap: 18px;
  background: var(--bg); color: var(--accent);
  transition: opacity .7s; text-transform: uppercase;
}
#loader.gone { opacity: 0; pointer-events: none; }
#loader .lmark { font-size: 12px; letter-spacing: .42em; }
#loader .lsub  { font-size: 9px; letter-spacing: .3em; opacity: .45; }
#loader .lbar  { width: min(220px, 56vw); height: 2px; background: rgba(159,192,255,.16); }
#loader .lbar i { display: block; height: 100%; width: 0; background: var(--accent); transition: width .15s; }

/* --------------------------------------------------------------- desktop */
@media (min-width: 760px) {
  :root { --pad: 26px; --safe-b: 24px; --safe-t: 20px; }
  .topbar { flex-direction: row-reverse; }
  .topbar .title { font-size: 11px; letter-spacing: .4em; opacity: .62; }
  .topbar .back { font-size: 11px; }
  .hud { right: auto; bottom: calc(var(--safe-b) + 22px); }
  .hud .alt { font-size: 40px; }
  .hud .label { font-size: 11px; }
  .hud .exp { font-size: 12px; }
  .hint { left: 50%; bottom: calc(var(--safe-b) + 22px); }
  .rail .tick { height: 30px; width: 46px; }
  .rail .tick:hover i { opacity: .85; width: 16px; }
}

/* ------------------------------------------- reduced-motion static stepper */
.rm-wrap { max-width: 720px; margin: 0 auto; padding: 72px 20px 100px; }
.rm-wrap h1 { font-size: 13px; letter-spacing: .4em; text-transform: uppercase; color: var(--accent); margin-bottom: 8px; }
.rm-wrap p.sub { font-size: 11px; opacity: .55; margin-bottom: 36px; letter-spacing: .1em; }
.rm-step { margin-bottom: 34px; }
.rm-step img { width: 100%; border-radius: 8px; display: block; box-shadow: 0 8px 40px rgba(0,0,0,.5); }
.rm-step .cap { display: flex; justify-content: space-between; align-items: baseline; margin-top: 10px; font-size: 11px; gap: 12px; }
.rm-step .cap .l { letter-spacing: .24em; text-transform: uppercase; color: var(--ink); }
.rm-step .cap .a { color: var(--accent); opacity: .75; font-variant-numeric: tabular-nums; }