Possible and not possible

Comparing more or less, before and after

There is a universal constraint that you cannot get around, whatever choices you make. Learn how to make a simple comparison of the before and the after the change you hope to make. These snapshots define the change.

Learn more about how the choices you can make runs up against this limit, which is the famous conservation of energy: the height of the orange bar(the energy shifted) afterwards has to be less than or equal to the energy before.