?

It works, because white is threatening c4. There is no way to stop it unless you give up the queen. So black opts to perptetual check the white king here (making it a draw). Does anyone understand?

yeah, it works. I couldnt solve it, though

i got it up until Nd6 but im pretty sure best play would result in a draw. The king is stuck protecting c3 and so the queen just has to alternate between checks and staying on d3....

the king cant run away because:

(figure after 5. Qd2+ king retreats back to b3 and queen goes back to d3, so it looks like move 4)

if the king tries to escape to b4 then, Qb1+. If the king tries to retreat further and goes Ka5 then Qa1+ forcing the king back or losing his mating pawn.

similarly if he tries escaping on the A file with Ka4 then simply, Qc2+ and white is in the same dilemna.