I have already built a cube-shaped box out of some wood panels I had lying around. It is perfectly solid, I can push it from every side and it will not tilt.
The next box should be not cube-shaped but taller than deep, let's say 20 cm tall, 20 cm wide and Z cm deep. If I make it not deep enough, for example 5 cm deep, it will be easy to tilt it by pushing it from the front.
How small can I make the Z depth while still making the box stable enough? Are there numerical/engineering rules for that?
What if I add more weight to the base? And how much does the weight and thickness of the walls of the box contribute to the stability of the box?