What Tetris Effect: Connected is
This is Tetris rebuilt around music and visuals. Over 30 stages each bring their own music, sound effects, graphical style and background, and all of it evolves as you play. The Tetriminos themselves react to the beat, so the board, the sounds and the effects stay in sync with how you're clearing lines. There are over 10 modes covering single-player, competitive and cooperative play. A mechanic called the Zone lets you stop time and stop Tetriminos falling, which you can use to escape a board that's about to top out or to bank extra Line Clears for bonus rewards.
Playing together
The multiplayer expansion is the main draw for a group. In "CONNECTED" mode, three players team up and literally connect their Tetriminos Matrices to fight against A.I.-controlled Bosses, so you're working as one shared board rather than against each other. "Zone Battle" is a one-on-one match of standard competitive Tetris with the time-stopping Zone mechanic added in. "Score Attack" and "Classic Score Attack" are single-player versus modes where two players compete separately to see who posts the best score. Cross-platform multiplayer lets you play with people on other platforms, and Friend Match rooms are joined with a Room ID. A Friend Match room can hold up to 8 people total, and Spectator mode is available there, with emotes spectators can use during the match.
Before you start
The game runs with an uncapped framerate and supports ultra-wide monitors, with 4K or higher resolutions available when Vsync is off. Expanded graphical options are included for both 2D and VR play, covering things like particle volume and size and texture filtering. There's a Tutorial tag on the game, so the modes and the Zone mechanic are worth a first run before you throw your group into a Boss fight.