A few years ago I spent a couple of days with friends in a cabin on a lake in New Hampshire. There were motor boats on the lake, but one evening, seeing no boats around, I decided to swim across the lake. As I was swimming, a large US Coast Guard boat approached me, and an officer, leaning over the side, asked me what I was doing.

The timer gives you 15 seconds to find the answer. It notes your errors but it only shows you the correct answers at the end.

If you don't use the timer you see the correct answers immediately and, in many cases, you can click on More Feedback to see a similar word or sentence.