: Use a tool like Tile Layer Pro to open the ROM and find the graphics (sprites) for the I-piece. You can redraw it, though its "hitbox" is defined by the code, not the art.
If "developing" means changing the actual look or dimensions of the long piece: Tetris Rom Mame
If you are looking to manipulate the game to give you more long pieces or change their behavior, here are the primary methods: 1. MAME Cheat Engine : Use a tool like Tile Layer Pro
: You can use the MAME debugger ( -debug ) to find the memory address that stores the "Next Piece" ID and manually freeze it to the value of the long piece. 2. ROM Hacking (Assembly) Tetris Rom Mame