Learn Dutch: Hoe groot de blaar ook is, hij blijft spelen. - However big the blister is, he keeps playing.

You use the pattern hoe + adjective or adverb + subject + ook + verb. Here, it is hoe + groot + de blaar + ook + is. Together, this creates a concessive clause meaning "no matter how big" or "however big."

Why isn't there word order inversion in the second clause? Shouldn't it be blijft hij spelen?

This is a special exception! Normally, starting a sentence with a subclause pushes the verb to the front of the main clause. However, concessive clauses starting with hoe ... ook are often treated as an independent thought outside the main sentence structure. Because of this, the main clause keeps its normal subject-verb order (hij blijft spelen).

Does ook mean "also" or "too" in this sentence?

Not here. In this grammatical structure, ook works together with hoe to mean "no matter how" or "however." Without ook, the first part would just sound like a regular question ("How big is the blister?").

How does blijft spelen translate to "keeps playing"?