The smile is incredibly encouraging for Thor. Knowing he's made her happy sort of just enables him to be even more of a goob.

"I most certainly did!" He beams, nodding his head quickly. "I can give you lessons if you'd li-UH." He cuts off mid sentence as she flings her arms around him, his cheeks turning just a little bit pink when she moves to kiss him. He doesn't so much as hesitate, though. He leans in and kisses her right back!

Happy birthday indeed.