This is the new ntris multiplayer client!
If you don't trust my certificate, you can play singleplayer ntris here, but you won't be able to log in or record high scores.

ntris by Shaunak Kishore
Use the arrow keys to rotate and move a piece and use space to place it. Press left shift to swap the current piece with the piece you're holding.
You can also use Z and X to rotate a piece, C to hold it, and enter to pause the game.