.flash { position: fixed; inset: 0; pointer-events: none; z-index: 9997; opacity: 0; }
.flashActive { animation: flash var(--duration, 150ms) ease-out; }
@keyframes flash { 0% { opacity: var(--opacity, 0.4); background: var(--flash-color, #fff); } 100% { opacity: 0; } }