From Hard Drop - Tetris Wiki

This category lists T-Spin methods. Articles in this category generally depict strategies involving twists with the T tetromino. To learn what a T-Spin is and how it defined, refer to the main T-Spin article. Please note that depending on certain game and certain rulesets and detection, different scoring and identification will be apparent. For example, a T-Spin Mini on Tetris Online Japan would count as a T-Spin Single on Tetris DS.

Main Article: T-Spin