"Reversible Trigger System" is a utility by Rushot. The utility shows how to use triggers to display unit energy like [|||||||||||||]. The energy goes up and down. When the unit is going up in energy and reaches the top, it gets extra attack; but when it is low or none, the unit has normal attack.
The utility was very creative. I don't think I've seen anything like this before. The complete instructions are on a word document and are clear. The scenario showing the Reversible Trigger system is only a mameluke and a section of wall, but it still gets the point across. Some people like playable utilities so they can see how they could use it in a certain situation.
Final Thoughts -
I recommend this utility, though it might be kind of hard to understand; as it is somewhat complex.