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It is literally explained in the first five minutes of the turorial

Or you can intuit from the score displayed after you cut each block

To be fair the tutorial wasn't always there. And when it was added I had no reason to go through it. Not the parent though.

Maybe you have a different one on a different platform but there is no score discussion there.

Intuiting things at 3 blocks a second is a challenge.

It's explained 3-4 levels into the campaign, not the tutorial you linked