That was not - expected. But that was the universe wasn't it? Always throwing the unexpected curve balls at you. He did smile slightly at the "can always punch later" adding as he walked through the door and closed it behind them; "Always. Always time for punching later."
The door being sealed, he worked on programming a setting for the room. Thank goodness for advanced technology that let this training area become whatever the people training in it needed it to become - and thank goodness for locked doors so no current students could wander in and possibly get hurt. Bucky's style of ... teaching ... had come a long way from the days in Russia where "students" getting hurt had been part of the training.
It didn't make him flinch (mostly, mostly it didn't make him flinch) to teach combat and in this case "being sneaky" to people.
"All right, you want sneaking up on people," he didn't say marks or targets and was proud of himself for that. "Or sneaking into buildings or both?"