In most Tetris titles, a player's score is incremented by completing "lines", where a row of brick pieces without gaps is removed from the 2D playing field. This action both earns points and clears the completed row, creating space for additional pieces. However, in Tetrisphere, the objective is to remove bricks by causing three pieces of the same type to touch as a result of a "drop". A drop occurs when any brick falls, either directly from the player releasing the currently held brick or when the supporting brick below it is removed by any means.
When three bricks of the same type touch, this triggers a "combo". During a combo, the three bricks glow brightly and implode, removing themselves from the playing field. Any other same-shaped blocks that are in contact with this combo will also be removed in a chain reaction. For example, if a player has lines of nested "Z" pieces and then drops another "Z" directly on top of one of the nested "Z"s, the dropped piece will cause the piece below to implode, subsequently triggering the removal of all identical pieces touching that piece, and so forth.
The only exception is that the pieces involved (including the original three) must adhere to the rules dictating which pieces are considered "touching". For instance, any two matching pieces that are stacked must be exactly on top of each other to be removed. Laterally, each piece follows specific rules based on its shape. To illustrate, "O" pieces (a 2×2 square, colored blue) and "I" pieces (a 3×1 or 1×3 rectangle, colored green or yellow) must maintain full contact on one side with a complete side of another piece of the same shape, while all other pieces are considered "touching" if any part of them makes contact with another of the same shape.
To facilitate combos, pieces can be moved by "sliding". A piece can be moved by sliding when the player lines up the shadow of the current piece they're holding with a same-shaped piece on the sphere. A mismatched shadow and piece cannot be moved in this way. Pieces moved with sliding can pass through and destroy crystal pieces, but they cannot move through other pieces themselves.
After a combo is finished, some random pieces on the sphere will start to glow; the number of pieces this affects is proportional to the size of the combo. Pieces that glow in this way are called "power pieces". A power piece possesses unique qualities compared to a normal piece:
First, if a combo is started with a power piece, the combo takes longer to finish. This allows the player to start additional combos while the first one is still ongoing. This increases the combo count and gives the player the opportunity to earn more points and magic.
Second, a power piece can be slid "up" one layer on the sphere. This allows power pieces to be easily moved around the entire sphere and enables the player to set up gravity combos.
Third, if a combo is started with a power piece, the player can then hold down the B button to slide the power piece just before it detonates, enabling them to start a new combo elsewhere on the sphere. This is called a "fuse combo".