In fact, they're not: it's really a very, very high-resolution input medium -- you have to just do it twice, you have to touch the screen and then rotate your finger slightly -- and you can move a cursor with great accuracy.
でも実際は かなり高分解能です 2度しか操作は必要ありません 画面に触って指を少し回せば かなり正確にカーソルが動きます