See this amusing reddit post. https://www.reddit.com/r/IndieDev/comments/1wfl64l/game_went...
I'm sure there's a named concept for this: the idea of the game is its selling point, and has to be revealed to consumers to market itself. But the market has low friction (via Steam distribution, and by copies being cheap to make w/ LLMs), so you can't reliably establish your product before masses take over, especially if you don't have reputation built up from previous games.
You have to be bringing in something else for this not to happen, trade secrets not present to the consumer being one such factor.
But you can copyright the artistic aspects of your game, like you can have the copyright to MONOPOLY and trademark the logo.
If you could patent gameplay there would be only 1 pong, which is a pretty basic idea. There are probably hundreds of pongs though.
It's a screenshot of a list of games on Steam. Half of them are called "Needle in a Haystack" and the rest are variations. The title says the game went viral a week ago and the original creator had to put "(original)" in the title.