[It's not so much that he doesn't want to talk to Gamzee; he actually does have a lot he wants to hash out here. It's just that he doesn't want to talk to him right now. He's been taking the day just to feel sorry for himself, and it's pretty obvious that he's been crying and is just generally being a big blob of pathetic, and he's allowing his lusus to hover around him and generally treat him like a wiggler for the time being, and none of that is how he particularly wants Gamzee to see him.

He doesn't notice Gamzee come in at first because he's too busy watching Hitch getting his cardio pump ripped out of his chest by his first flush crush and relating so hard. But Crabdad notices and sort of hisses threateningly, so Karkat will look up from his movie.]

I'm glad fucking doors mean nothing to anyone here. I mean, why would having my door shut mean anything other than please invite yourself in, I'm looking forward to company right now?