In some games, you must solve a puzzle and to do it, you have to transform the shapes that are present on the screen.
Change a triangle in a circle does not appear to have some interest but... When you have a round shape, it begins to roll and can thus fall and drop to the desired location.
In the same way, to change the scale of a shape can balance or unbalance a construction.
This type of games requires to think. One of the most famous is probably Replaceable Blocks, in which you have to switch and to transform shapes.