This is a good motivator for brushing, but it doesn't focus on each part of your mouth. Also, to get coins, you have to brush fast, but brushing too hard isn't good for your gums or teeth, so when it encourages this it disappoints me. There are several kids in the family, so when they take turns, they get less and less coins each time. I think you should make an animation in the corner for which parts of the mouth to brush, deal plenty of damage even if the person is brushing at a regular pace, and make it possible to have several profiles. These would be great improvements.
Edit: Why is it only 1 minute? A good brushing time is two minutes.