/**
 * Procedural level backdrop.
 *
 * Two canvases cross-fade on level up: one is visible, the other is generated
 * off-screen and then faded in.
 *
 * SCRIM BUDGET — read before changing these numbers. Muting is multiplicative:
 * the generator's visible contribution is (1 - scrimAlpha) * --bg-intensity.
 * An earlier version stacked a 0.72 scrim on top of 0.6 opacity and dark
 * generators, leaving 16.8% of an already-dark colour and rendering the
 * backdrop indistinguishable from plain black.
 *
 * Gameplay contrast does NOT depend on this scrim — the playfield has its own
 * 92%-opaque slab and the panels are fully opaque. The scrim only softens the
 * backdrop behind them, so it can stay light.
 */

.backdrop {
  position: fixed;
  inset: 0;
  width: 100%;
  height: 100%;
  z-index: -2;
  opacity: 0;
  transition: opacity var(--dur-bg-fade) var(--ease-out);
}

.backdrop[data-visible="true"] {
  opacity: var(--bg-intensity);
}

.backdrop-scrim {
  position: fixed;
  inset: 0;
  z-index: -1;
  pointer-events: none;
  background: oklch(0.14 0.012 265 / 0.35);
}

/* Intensity "Off" skips generation entirely in JS; this just guarantees nothing
   is painted even if a canvas was already populated. */
:root[data-bg="off"] .backdrop,
:root[data-bg="off"] .backdrop-scrim {
  display: none;
}