Higher settings send warheads faster and in greater numbers, and from wave three some of them split partway down into several smaller ones.

Every warhead in the air gets a different starting letter, so a keypress is never ambiguous.

Fades a keyboard across the play field and lights up the next key, colour-coded by the finger that should press it. When stuck keeps it hidden until you miss three keys in a row, then shows it until you get one right.