To call this game "Tetris on a sphere" would be a bit disingenuous. It's far, far more complicated than that. Tetris merely requires you to place falling pieces such that they create solid, dissolving rows and thus abate, if temporarily, the peril of becoming overwhelmed by the steady stream of burdens in what I can only assume is a clever metaphor for adulthood. Globulous, on the other hand, has a clear goal: clear out layers of the sphere and reach the prize inside. It's the method that gets complex.
The gameplay is a little difficult to grasp at first (as is any puzzle game that operates in 3D), but thankfully there are plenty of tutorials.