B-MAT(ビーマット) | ２つの「考える」で学力センスを鍛えるためのシステムです。

The polyhedron is the unit which you should tackle in the next stage after you became able to fully understand (to fully image in the mind) the "development chart".
Therefore, if you understand (image) the "development chart" insufficiently, it also affects the understanding (imaging) on the polyhedron sometimes. In such cases, attend the quick training of development chart before tackling with the polyhedron.

If you really don’t improve with the polyhedron training within your computer screen alone, actually make the development chart of the question yourself and check the answer.
But since the making of the actual thing (the development chart) does not mean that you can quickly make the polyhedron, you have to repeat it many times without quitting. Just as in other trainings, repeat the following sequence:
With actual thing => in your head => with actual thing => in your head

Spatial perception applications