I like it when they make a fuss over them. And when the kids pick them up, they are usually very careful. Once in a while they get ruined. It takes about a half-hour of tapping. And that one wasn't shaken out.
Circles are tough.
I put a penny on top of the screen and try to trace it. It makes the drawing almost faded. There's just a silhouette of the object on the screen. Then you can retrace it. It also repairs a lot of mistakes.