Tetrisphere's Lines mode can be enabled for single player and multiplayer by entering LINES as your name and must normally be reentered every game session.
This hack permanently unlocks this secret mode as well as a level selection screen without having to enter any codes.
In Lines mode, pieces cannot be dropped and the player has a permanent wild card piece in hand. Chains are started by releasing a held piece by or on top of two or more of the same type of piece. Going into Lines mode and then exiting to enter Practice mode allows you to practice with Lines mode rules.
Database match: Tetrisphere (USA)
Database: No-Intro: Nintendo 64 (v. 20210220-053642)
File/ROM SHA-1: 32ADAA274CEED246AEEE9F53592D642A121F3BDB
File/ROM CRC32: 70A3A5CE