Here goes: the objective is to place some function devices on certain squares to extract balls from one square and transfer them to the destination.
The two main tools are: the one that pushes/pulls and the one that rotates it. During the Build mode, you place your tools on the grid. During the Sequence mode, you test out your design. Besides moving tools from 1 square to another, you can: change the rotation from clockwise to counter clockwise. Or from pushing to pulling.
Things can get very complicated when one tool changes the position of another tool!
There are 72 levels. I can easily see why some folks would love this game. I've done less than half the levels.
Hard Logic is Max's other game. I like it better.
If you really like [the Sequence], then you should definitely check out Perfect Paths.