Given the task definition and input, reply with output. Generate a question which can yield the answer mentioned in the input. Generated question must be answered by the answer provided in input, without using any extra knowledge.

Context : TetriNET is a multiplayer online Tetris game for up to six people, developed by St0rmCat in 1997 that supports team play.
Answer : Tetris
The TetriNET is based upon what?