add the word "game" to description

This change prevents an awkward garden-path reading that makes it look like there's no noun, or that DIVE is a theory. It is not. It is a fact. @alexfink

(The incorrect reading, which kept me from figuring out the intended meaning for a few days, is akin to "Dive is an additive, multiplicative, blending, and Threes-like number game.")

.