The deal here is that these little test tube things will be going by, and you need to open or close the containers of markers to fill those test tubes in the pattern shown at the right.

Confused? Save your game, then push the start button to see what's going to happen.

Okay, now you get the idea. The way you determine whether a marker falls into your tube or not is to close the container (by clicking on it); they're all open at the start, as you can see by the green lid hanging down.

The difficult part of this task is that after the first run, you'll be filling multiple tubes, and the second one starts before the first one is done. So you need to plan out which markers you're going to drop to make sure the right markers are available for tubes 2, 3, and 4. Read to the end of this hint for one way to do this.

This is another good place to play the game in a window so you can freeze time and think.

It's important to plan ahead. The only red marker available for the third round may be two levels up, so make sure you remove the first two levels of markers before you get there.

Finally, you should know that there's no point in saving halfway through; all saves return you to the first round (oy). So you'll have to beat all five rounds in one go in order to move on.

There may be other ways of doing this, but here's how I did it: