Someone on the Compulsion Games forum for We Happy Few was concerned that there is another game out there, Lisa the Painful, where people take a happy drug called Joy. Did we steal the idea?
No, obviously not. I came up with the name Joy in roughly February 2014. That game came out in December 2014. (I had to look it up; I've never heard of it.)
The reason we called our in-game drug Joy is it makes you really happy. Joy is the #1 English word for "surpassing happiness." Probably anyone who was looking for a name for a drug that makes you really happy would at least consider the word "Joy."
I can't take credit for the happy drugs idea. One of our inspirations was Aldous Huxley's Brave New World, which is about a society where people take a pill called "soma." But our main inspiration is North American happy culture. Depressed? Take a Prozac. Stressed? Take a Valium. Bad news? Don't put it on Facebook! Only Downers put bad news on Facebook!
(Not that I'm against anti-depressants. They help a lot of people.)
Point is: talking about happy drugs is an obvious thing to do if you live in our society, just as making a movie about alcoholics was obvious in 1950.
As a screenwriter and story editor, I've seen any number of my ideas duplicated in films and TV shows I didn't write, sometimes produced by production companies that saw my pitch. That's not because my ideas were stolen. It's because certain ideas are bubbling up to the top of the zeitgeist stew at any given time. I was pitching a hacker action movie a year before The Net came out. But so was everyone else. I was pitching a Pretty Boy Floyd movie a year before Larry McMurtry was tapped to develop a Pretty Boy Floyd project.
Roger Corman was asked about the similarities between his cheapo film Carnosaur and Jurassic Park. "Steven Spielberg is an honest man," said the King of the B's. "I don't for a second think he would steal my idea!"
You can't copyright an idea; you can only copyright the execution of an idea. You can't copyright "game about people who take happy drugs" because making a game about people who take happy drugs is "obvious." Anyone can get there by just observing the world. What makes our game unique -- or the other game unique -- is how that idea is elaborated in plot and character.