There may be rules to the contrary, but my common sense tells me that you have a singular subject. Your singular verb "is" is correct, but your plural complement "blocks" is not. Offhand, I can't think of an example where a gerund subject would take a plural verb, unless the gerund is plural, or there are two of them.
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Eddie88 Do you think you would natually use the plural form in speech too (because of GOALS)? Or are you more versed in this department haha.*** blessed or cursed me with an ear for agreement. I never ***** up!