From Hard Drop - Tetris Wiki
Fumen is a tetris field situation editor written by Mihys that allows for various field setups and moves to be illustrated with more clarity than normal. the official version is Japanese, but Hard Drop has provided an English version that links back to the official site. Another forum member has seen fit to create a second translated version here. Fumen is still in active development. The latest version (1.10e2) was released on 10/28/2010.
 Basic Usage
 Field block setup
To set up the general setup of the field, select one of the eight dark-colored radiobuttons at the top to represent the color to be used for the occupied spaces on the field. Removal of complete lines is done automatically, and so is the moving of lines down from above as a result of line clears. clicking on an occupied tile will either change it to the color you selected or clear it.
 Piece selection and placement
To select a piece, use the bright-colored radiobuttons in the second set of radiobuttons and then position the piece where it should be in the field at that "step" (where "step" is an important position in that particular move). If this is NOT the final resting place of the piece (I.E. the piece does NOT lock there), click the ミノ接着 ("LOCK" on the english version) checkbox in the third set of options (immediately below the second set of radiobuttons).
 Frame Management
To put a caption on a frame, enter it in the textbox immediately above the previous frame, next frame, and "remove frames after" (english name in Zeta's translation) buttons. Captions that are too long will not be displayed in full. Use the ▼ 次ページ button to move to the next frame (new frames are added as needed). the ▲ 前ページ button backtracks one frame, and the × 次ページ以降を削除 removes all frames after the current one.
 Outputting code and URL's
to output the URLs used to access your setup, click the ★ データ出力 (OUTPUT CODE) button to create the code for your setup. this will also generate two url's. the one that contains "?m" is used to view the setup, the one containing "?v" is used to modify it. currently, the codes output by the english version are identical to those made by the japanese version, and this will remain as such until the next version of Fumen is created and released.
The latest version (1.10e2) adds support for tinyurl, piece preview on mouse hover, line clear effects, quiz mode, and more.