Bucky actually jumps when he hears the new voice, looking around for anyone else in the lab. He'd thought that they were alone and now he's worried about what might have been overheard. But then he realizes that the voice is coming from a speaker; that Tony is, actually, talking to one of his computers. It's like something out of Star Trek and Bucky can't keep the amazement off his face. He's starting to wonder if he really did fall down some kind of rabbit hole, if this is his Wonderland even more than he could have possibly dreamed.

"It's amazing," he breathes; this is far, far above any of the technology that Bucky's ever actually had in his own hands. He's kind of forgotten about the shirt, lost in the way Tony so easily manipulates the diagram, how he pulls and twists and manipulates, easy as breathing. "You're amazing. You're some kind of miracle, aren't you?"

Tony's also someone that, if he can do even a fraction of what he thinks he can, Bucky knows he'll never be able to pay back. Part of this all still feels like a dream and he's holding onto those good feelings, not wanting to let go of the illusion too soon.