7

One of the most fun thing about Tetris is playing against someone else. Considering the basic controls (3-6 buttons) and simple layout it is really well-suited for two player single-keyboard play. This simplicity also makes it well-suited to low-bandwidth network play. I've even seen network play over a graphing calculator link cable, which is very low-bandwidth to say the least.

Kblocks, however, has no multiplayer of any kind, neither single-keyboard nor network play. I think this is a serious omission. At the very least it should have single-keyboard 2 player. Network play would be a nice but non-essential extra.