html, body {
  margin: 0;
  height: 100%;
  overflow: hidden;
  background: radial-gradient(ellipse at center, #2f8fb3 0%, #17607d 70%, #0f4a62 100%);
  font-family: "Malgun Gothic", "Apple SD Gothic Neo", sans-serif;
  -webkit-user-select: none;
  user-select: none;
  -webkit-tap-highlight-color: transparent;
  touch-action: none;
}
#stage {
  position: fixed;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}
#book { position: relative; }
.page { background: #fff; overflow: hidden; }
.page img { display: block; width: 100%; height: 100%; pointer-events: none; }
.regions { position: absolute; inset: 0; }
.region { position: absolute; cursor: pointer; box-sizing: border-box; }
body.hl .region.playing:not(.layer0) {
  outline: 3px solid rgba(255, 190, 0, 0.95);
  background: rgba(255, 200, 0, 0.22);
  border-radius: 6px;
}
.region .lbl { display: none; }
body.debug .region { outline: 2px solid rgba(255, 0, 0, 0.85); background: rgba(255, 0, 0, 0.08); }
body.debug .region.layer0 { outline-color: rgba(0, 120, 255, 0.85); background: rgba(0, 120, 255, 0.05); }
body.debug .region .lbl {
  display: block; position: absolute; left: 2px; top: 0;
  font: 700 12px/1.2 Arial, sans-serif; color: #c00; background: rgba(255, 255, 255, 0.85);
}
.nav {
  position: fixed; top: 50%; transform: translateY(-50%);
  width: 44px; height: 64px; border: 0; border-radius: 10px;
  background: rgba(0, 0, 0, 0.35); color: #fff; font-size: 34px; line-height: 1;
  cursor: pointer; z-index: 5; padding: 0;
}
#prev { left: 6px; }
#next { right: 6px; }
#info {
  position: fixed; bottom: 4px; left: 0; right: 0; text-align: center;
  color: #fff; font-size: 13px; z-index: 5; display: none;
}
body.debug #info { display: block; }
#start {
  position: fixed; inset: 0; z-index: 10;
  display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 18px;
  background: rgba(15, 45, 65, 0.92); color: #fff; text-align: center; padding: 24px;
}
#start[hidden], #startBtn[hidden] { display: none; }
#msg { font-size: 18px; margin: 0; line-height: 1.5; }
#startBtn {
  font-size: 24px; padding: 14px 36px; border: 0; border-radius: 44px;
  background: #ffc400; color: #222; font-weight: 700; cursor: pointer;
}