Los Angeles, United States (AFP): The makers of irreverent party game "Cards Against Humanity" are suing Elon Musk's SpaceX for $15 million, claiming it dumped "gravel, tractors and space garbage" on pristine land.

A lawsuit filed in Texas on Thursday said SpaceX had invaded property owned by the game company, which sits next to its Starbase, and "treated it as its own for at least six months."

"Elon Musk's SpaceX was building some space thing nearby, and he figured he could just dump his shit all over our gorgeous plot of land without asking," read a website detailing the lawsuit.

"After we caught him, SpaceX gave us a 12-hour ultimatum to accept a lowball offer for less than half our land's value."

The company said it declined the offer and began legal action.

Cards Against Humanity is a game based on amusing and irreverent answers by players to topics suggested by the cards.

The company relied on crowdfunding for the game's initial development in 2010. It uses a series of pranks and stunts highlighting what it says are injustices as part of its marketing strategy.

At the heart of the suit is a parcel of land on the US-Mexico border that Cards Against Humanity LLC bought in 2017 in an effort to stymie the construction of a border wall pledged by then-president Donald Trump, using thousands of $15 pledges from users.

"150,000 people gave us their hard-earned money, and in exchange we vowed to protect this land from racist billionaires and their dumb vanity projects," the website says.

"We promised we'd use every legal tool at our disposal to protect this land from bullies like Trump and Musk (who's spending millions to get Trump elected...)," the firm said.

All original contributors stand to get up to $100 each if the company prevails in its lawsuit, it said.

There was no immediate reply from SpaceX to an AFP request for comment.