Quadra

Quadra was originally developed and marketed by Ludus Design, but became open source software in August of 2000. Because of this, the game evolved some unique features. Quadra was much different from Tetris from the start. Unlike many fan games from its time, the name of it didn't end with -tris.

Features
It implemented recursive gravity. An average player can clear nine lines or more.

Quadra rewards more for higher line clears, unlike games using the scoring system of Tetris Worlds Cascade, which rewards more for higher cascades.

Quadra's rotation system is mostly identical to left-handed Nintendo Rotation System except for the I-piece being 1 cell lower on the vertical state.

It has 3 rotation buttons, the extra one being double rotation. The rotation buttons work differently from most other Tetris games: they will fire on the key-up moment rather than key-down.

It has a short (to be measured) constant spawning delay and also line clear delay. These delay functions like in the TGM series: a player can move and/or rotate once (not needing to hold the button down), and after the animation, the piece will preform those actions. But they're different in detail.

The initial rotation functions as "any number of key-up events of exactly one rotation button during the delay schedules an initial rotation in that direction".

The game has adjustable DAS, along with some special characteristics. After pushing one direction, pushing the other direction simply stops the piece (won't immediately move in the other way), and when one is released, the piece moves towards the other by 1 cell and enters DAS delay. It does not preserve DAS across pieces. The initial move functions as follows: If exactly one of the move buttons has been in 'pushed' state at any time during the delay, the piece will move by 1 cell when spawned. And if exactly one of the move buttons is pushed down on the spawning moment (multiple could have been pushed during the delay, they don't affect this), the piece will move by 1 cell (but won't do it the second time if the previous one has been executed) and enter DAS delay.

The above detailed differences on DAS and rotation may cause most other Tetris players to feel weird and take time to get used to.

The game also has optional smooth piece falling like that of The New Tetris.

With the presence of fast DAS and double rotation, top players have been seen to build at peak speeds upwards of 260 TPM, although for a short duration. The game displays "blocks per minute" of even higher, but these measurements aren't in real time.

Quadra also features demo recording and playback, multiplayer online, and an online high score table where spectators can download the demos of the top six games.

Records
Multiplayer

BPM(BlocksPerMinute) 324 set by "Henke". The holder of the former BPM rec were kdjoony with 314

PPM(Points Per Minute) ~500 000 set by [qz]-Fawk- with two clean canvas. Without clean canvas the rec is ~300 000 set by RZ***Pistje

Singelplayer

The top 100 Highscores (web archive)