N-Blox

N-Blox (or "Neave Tetris") is a singleplayer Tetris flash game available on websites like neave.com, freetetris.org and tetrisfriends.com. It started as an unofficial game which was just called "tetris". It was programmed by Paul Neave in 2003 who had made another Tetris version on his website before. Despite being a very simplistic game, it was the first result when googling for Tetris. So, The Tetris Company threatened Neave with legal actions and later made an agreement with him (in early 2009). For a long time, tetris.com linked to N-Blox as "play Tetris".

Gameplay
N-Blox is some kind of classic Marathon game. It comes with only 1 preview, no Hold feature and no lock delay. Newer versions feature hard drop beside soft drop and use an easier randomizer. Level increases every 10 cleared lines whereas gravity doesn't increase anymore after level 10. As a result, many people can play N-Blox pretty much forever.

The scoring system is similar to that of old Nintendo games: A Single scores 40 points, a Double 100 points, a Triple 300 points and a Tetris 1200 points. Those points are multiplied with the current level. As a result, a player will roughly quadruple the score when playing twice as long. The game also gives 1 point for each row a piece has fallen down but those points are just marginal on later levels.

The version at tetrisfriends.com has a global leaderboard.

Randomizer
The original version used memoryless randomizer, that means the piece order was totally random. The newer official version uses 8-bag randomizer whereas the first piece of the very first bag isn't handed out. 8-bag randomizer means that each bag consists of 8 pieces and every shape is contained in a bag (plus one random shape). The longest possible drought is 15 pieces (next I piece will show up after 15 pieces at least), and there are never more than 4 pieces of the same shape within 10 pieces (e.g. no flood of 5 S pieces within 10 pieces).