/* ============ settings — change colours and fonts here ============ */
:root {
  --bg: #000;
  --fg: #fff;
  --dim: rgba(255, 255, 255, .42);
  --font: "Inter Tight", system-ui, sans-serif;
  --ease: cubic-bezier(.2, .7, .1, 1);
}

/* ============ base ============ */
* { box-sizing: border-box; margin: 0; padding: 0; }

html, body {
  height: 100%;
  overflow: hidden;
  background: var(--bg);
  color: var(--fg);
  font: 500 12px/1.35 var(--font);
  letter-spacing: .01em;
  -webkit-font-smoothing: antialiased;
}

a, button {
  color: inherit;
  font: inherit;
  text-decoration: none;
  background: none;
  border: 0;
  cursor: pointer;
}

.dim { color: var(--dim); }

/* ============ the 3D book ============ */
#book {
  position: fixed;
  inset: 0;
  width: 100vw;
  height: 100dvh;
  display: block;
  opacity: 0;
  touch-action: pan-y;
  transition: opacity 1.2s var(--ease);
}
#book.ready { opacity: 1; }

/* ============ corner UI ============ */
.ui {
  position: fixed;
  z-index: 2;
  display: flex;
  gap: 18px;
  padding: 22px 26px;
}
.tl { top: 0; left: 0; flex-direction: column; gap: 2px; }
.tr { top: 0; right: 0; }
.bl { bottom: 0; left: 0; flex-direction: column; gap: 2px; }
.br { bottom: 0; right: 0; align-items: center; }

/* nav links: underline slides in on hover */
.tr a { position: relative; color: var(--dim); transition: color .3s; }
.tr a:hover, .tr a.on { color: var(--fg); }
.tr a::after {
  content: "";
  position: absolute;
  left: 0; right: 0; bottom: -3px;
  height: 1px;
  background: currentColor;
  transform: scaleX(0);
  transform-origin: right;
  transition: transform .45s var(--ease);
}
.tr a:hover::after, .tr a.on::after { transform: scaleX(1); transform-origin: left; }

/* spread title: rolls up when the page changes */
.cap { height: 16px; overflow: hidden; }
.cap span { display: block; transition: transform .6s var(--ease); }

/* progress bars */
.bars { display: flex; gap: 4px; }
.bars button { position: relative; width: 18px; height: 14px; }
.bars button::before {
  content: "";
  position: absolute;
  left: 0; right: 0; top: 6px;
  height: 2px;
  background: rgba(255, 255, 255, .18);
  transition: background .3s;
}
.bars button:hover::before { background: rgba(255, 255, 255, .6); }
.bars button.on::before { background: var(--fg); }

#play { min-width: 38px; text-align: right; color: var(--dim); }
#play:hover { color: var(--fg); }

/* ============ about / contact overlays ============ */
.panel {
  position: fixed;
  inset: 0;
  z-index: 1;
  display: grid;
  place-items: center;
  padding: 24px;
  background: rgba(0, 0, 0, .86);
  opacity: 0;
  visibility: hidden;
  transition: opacity .5s var(--ease), visibility .5s;
}
.panel.open { opacity: 1; visibility: visible; }
.panel > div {
  max-width: 520px;
  font-size: clamp(20px, 2.4vw, 28px);
  font-weight: 400;
  line-height: 1.25;
  transform: translateY(12px);
  transition: transform .6s var(--ease);
}
.panel.open > div { transform: none; }
.panel p + p { margin-top: 1em; }
.panel .dim { font-size: 12px; font-weight: 500; }
.panel a { border-bottom: 1px solid var(--dim); }

/* ============ small screens ============ */
@media (max-width: 640px) {
  .ui { padding: 16px 18px; }
  .tr { gap: 14px; }
}

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