He wasn't just watching her attacks as she moved around the room. He was also studying how the objects in the room transformed without any obvious signal, leading him to the conclusion that it may be possible to control the room.

When she stopped, he did a quick experiment, the end result being something similar to Vanko's drones appearing. Moving quickly, he dispatched them all with quick repulsor bursts. It was tempting to use some of the other various weapons concealed in the suit, but it didn't seem all that wise to waste ammunition when he had absolutely no idea if he'd be able to replace it.