Goal: keep the grid clear. Cyan sparks flicker on — tap them fast.
If you leave a spark too long it spreads to a neighbouring cell (and turns
orange as a warning). Let too many pile up and the grid overloads — game over.
Clear sparks in a row to build a combo multiplier. But red nulls
are decoys — never tap them (they vanish on their own). One wrong tap ends the run.
Controls: tap/click a cell, or move with the arrow keys and press space.