That, I'm afraid, is essentially game over. Do they have a case? No. Not really. I am convinced that if it went to court, the "copyright" claim would get thrown out completely. The trademark, perhaps not — but if I changed the name, to e.g. "Trys", that would be much harder for them to argue.
But, like most of us, he's not keen on the idea of taking on a big company like "The Tetris© Company" so that he can offer his Tetris©-alike game. You can still find Tris (not to be confused with Tetris©) for free in the App Store as of this writing, so go grab it.
For what it's worth, "The Tetris© Company" has gone after pretty much every other Tetris©-alike game on every other mobile platform out there, so this is a long piece© fitting into just that one four-by-one slot© for "The Tetris© Company:" something they work very hard at achieving and when they get it, their eyes light up with joy at having cleared their board.
Oh, and for good measure: Tetris© is a trademark of "The Tetris© Company." ©©