Hello I am looking for feedback on a invention process. I have a idea and technical drawing of a idea for a military application. Unfortunately when searching patent office website found a existing patent that covers a product that does a similar function but does it with a totally differnt method and mechanism that what I was considering. My question is what degree of differnence to a existing patent must my better mousetrap encompass. Must my product be 100% different than existing , 50% different etc. Does anyone know what legal lithmus test is? I appreciate any feedback or suggested articles to read.