Do your homework. Lose the pettiness. Karma is more in-depth. This is just a small part, explained a certain way for understanding. ‘The Twelve Sacred Principles of Karma’, The Fifth Principle, Law of the Mirrors.
Law of Karma - every action generates a force of Energy that returns to us in like kind. What we sow is what we reap. When we choose actions that bring Happiness and Success to others, the fruit of our Karma is Happiness and Success .
This is how it is. You do all things to serve others and gain positive karma. Avoid gossip and hateful thoughts, for that creates negative karma. In all you do, do it for good, and do it so it will help and serve others.