Shape creation?

I was wondering if there’s a way to create a shape from a button press.

Like in the game Incredibots.

And maybe a free form drawing shape?

A few more questions:
Is is possible to make it in a 2D interface menu, then with a simple click of a button, it turns into a 3D interface?

Could I have just 3 simple shapes? Triangle, Circle, and Rectangle?

Then is it possible to have joints?

Thanks!