This is a lot harder than it looks. Often, you must click on the clear balls at the same time to clear the level. On some levels, timing is critical. You must get the balls to roll at the precise time. This often demands the near simultaneous removal of the gray balls.

Indeed, this is one of the harder physics games on the site to master. The second level is already quite difficult to do on a PC. You might have an easier time playing on mobile, where you can press on things simultaneously. Expect a lot of trial and error early on. This game is ideal for people who like brain teasers. It will keep your mind occupied if you have time to kill.