I'm not going to sell it,imakeing it just for practice, nevertheless, the Tetris Company owns a copyright of its source code and of certain audiovisual effects of Tetris. This means that I can?t hack into the Tetris Company?s codebase, and copy-and-paste it into my own program. Nor can I steel their music and graphic files and insert them into my program.
However, I can create my own game (using my own source code, music, and graphics) based on the unpatented Tetris game idea and distribute it publicly.