Smooth cube rotation exactly 90 degrees

Questions & Answers
1

Hello,
I am new to Unity3D and want to improve myself. I try to rotate a cube smoothly on 90 degrees around its own axis if button is clicked. It is easy on the first look, but rotating the cube its local axis are changed in the global space, so when I try to rotate it around Y axis (Vector2.up) I expect it will be rotated in all cases around the global Y axis that is not changed, because the local Y is on another place in the space.81832-unitycube.png

You can see better on the picture what I mean. Here the cube Y axis is more like X axis, but again I want to rotate around default Y axis that in this case is Z axis. After many rotations I do not know where is my Y, X or Z axes.
Can you help me ?

Thanks

2

transform.RotateAround(transform.position, Vector3.up, 20 * Time.deltaTime);

3

On the attached picture my Y axis is more like x axis in the global space. So I want to rotate vertical again and in this case around Z axis, because it is the vertical in the current situation.