Even Optimus paused briefly in surprise, engine jumping at the sound of that click.

"...Well. Well. Definitely not bored, I'd say." He laughed softly, low and aroused. His hand hovered for a moment, more out of brief indecision than any pointed desire to tease out more static - though a small crackle or two still snapped between them, before he ghosted the barest edge of a fingertip along the exposed indentation of paneling.

...Then he slapped his hand down on the edge, full palm catching the rim, though he used far less force than usual.

Interfaces were such sensitive things, and Optimus wanted to skirt the edge of pain and pleasure.