Three hours for Kirk's first foray into kal-toh resulting in a completed sphere. That is beyond remarkable, and perhaps that becomes obvious in the way his gaze shifts again to the set and back to Kirk, something not surprise but certainly interest in his eyes.

"I see." He also sees the way Kirk is looking at him, and it is pleasant to think that he is finally giving him something that actually challenges him intellectually. He is not, in fact, thinking about being flirted with, because he does not believe that Kirk would be interested in him in that way.

The invitation sparks a thought in him, but he must clarify— "I do not drink coffee. I do drink tea, and should the cafe also have that available I would find it enjoyable to go with you."

But surely Kirk just wants to do so as roommates, acquaintances, whatever term Vulcans use for the Terran definition of "friend" that is so unlike their own. However, that does not stop Spock from glancing at him out of the corners of his eyes as he continues to inspect the set.

"Two and a half hours to progress this far is less than anticipated." It is clear in the way Spock says it that it is a statement of fact, not a dig in any way: Spock had until now been unfamiliar with the speed Kirk is able to complete the puzzles.