Here's a tool you can use to tease out the mechanics of any RPG's task resolution/action system. It's based on attribution theory, which in layman's terms is the study of the factors that contribute to achievement. Google it if you're interested. Anyway, this is a simple matrix that defines each factor in a task resolution system as internal or external, constant or variable. Ability is constant. It's represented in most games as your skill level or ability score or ability modifier. Task difficulty is almost always set by the DM as the standard you need to reach in order to succeed. Effort usually appears only in systems that use dice pools or spell points or any other rule that allows the PC to buy advantage at the cost of some other finite resource. Luck is whatever the die roll adds to the PC's attempt. The first matrix is blank, for you to copy and print for your personal use. The second matrix I have filled in to give you an example. It's a way of standardizing how you look at game mechanics, whether you're designing your own or making a comparative study of other RPGs. Enjoy!