They don’t own the mechanic of falling blocks. I play many tetris fan games and they just have to avoid tetrimino (a misspelling of tetromino) and the word tetris and the tetris song. They also have to avoid steam and other stores just in case the tetris company fights them.
The subject matter isn’t the parodied thing. It’s not making fun of Tetris. It’s using Tetris in a pretty unrelated way to its actual purposes.
I’m not sure Tetris has a case here though. Do they have a patent on colored blocks falling down? You’re not even making rows clear
They don’t own the mechanic of falling blocks. I play many tetris fan games and they just have to avoid tetrimino (a misspelling of tetromino) and the word tetris and the tetris song. They also have to avoid steam and other stores just in case the tetris company fights them.