While not trying to strawman-ize intelligent design, it boils down to:

Some features of organisms are so complex that they couldn't have evolved randomly. There must have been some Intelligent Designer to direct macro-evolution.

Here's an example that contradicts this view. It shows that something as complex as the nervous system started out as something simpler, then was adapted to a different purpose.

Examples like this are great. They aren't likely to convince anyone who already believes in ID, but hopefully they'll dissuade others from seriously considering it. But examples shouldn't really be necessary, because ID has an internal flaw.

To restate ID: (and now I'm making a strawman)

I can't imagine how such complex things could have evolved naturally, so there must be some supernatural reason.

The form of the argument demonstrates only the limitations of the believer's imagination. The inability to imagine other solutions doesn't prove there are no other solutions, or that your solution is correct.