/* ============================================
   SCROLL ANIMATION SYSTEM
   Project-wide scroll-driven entrance animations.
   See Notion: 🎬 Scroll Animation System — Spec
   ============================================ */

/* --- Pattern A: fade-up entrance --- */

.anim-fade-up {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 500ms ease-out, transform 500ms ease-out;
  will-change: opacity, transform;
}

.anim-fade-up.is-visible {
  opacity: 1;
  transform: translateY(0);
}

/* Stagger: parent class triggers nth-child delay on direct .anim-fade-up children */

.anim-stagger > .anim-fade-up:nth-child(1) { transition-delay: 0ms; }
.anim-stagger > .anim-fade-up:nth-child(2) { transition-delay: 100ms; }
.anim-stagger > .anim-fade-up:nth-child(3) { transition-delay: 200ms; }
.anim-stagger > .anim-fade-up:nth-child(4) { transition-delay: 300ms; }
.anim-stagger > .anim-fade-up:nth-child(5) { transition-delay: 400ms; }
.anim-stagger > .anim-fade-up:nth-child(n+6) { transition-delay: 500ms; }

/* --- Pattern B: progressive scroll-driven zoom --- */

.anim-scroll-zoom {
  transform: scale(var(--scroll-scale, 1));
  transform-origin: top left;
  will-change: transform;
}

.anim-scroll-zoom--anchor-tl { transform-origin: top left; }
.anim-scroll-zoom--anchor-tr { transform-origin: top right; }
.anim-scroll-zoom--anchor-center { transform-origin: center center; }

/* ============================================================
   Pattern C — progressive scroll-driven fade.
   Element opacity tracks scroll progress continuously.
   p=0 (entering): opacity 0 — p=0.5 (centred): 1 — p=1 (exiting): 0
   Default --scroll-opacity: 1 so element is visible before JS init.
   ============================================================ */
.anim-scroll-fade {
    opacity: var(--scroll-opacity, 1);
    will-change: opacity;
}

/* --- Reduced motion override --- */

@media (prefers-reduced-motion: reduce) {
  .anim-fade-up {
    opacity: 1;
    transform: none;
    transition: none;
  }
  .anim-scroll-zoom {
    transform: none;
  }
  .anim-scroll-fade {
    opacity: 1;
  }
}