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".
The player can achieve higher scores by increasing the "combo multiplier". The combo multiplier indicates how much each combo is multiplied by when the combo is completed. The combo multiplier starts at 1x and has a maximum value of 20x. It can be increased in the following ways:
Gravity combo: By sliding pieces below one above it, a piece can fall due to gravity. If the piece falls and there are at least two other adjacent pieces of the same type, a gravity combo will start automatically without the need to normally drop a piece. The combo multiplier can be increased by up to ten times in this manner.
Fuse combo: By starting a combo with a power piece, the power piece can then be moved by sliding it over to start a new combo before it is removed. The combo multiplier can be increased by up to eleven times in this way.
In the "Vs." modes (both against the CPU and against another human player), the combo multiplier serves an additional purpose by increasing the effective rate at which garbage is sent to the opponent.
If a combo results in 20 or more pieces being removed, no power pieces will appear on the sphere. Instead, the player will be rewarded with an item of "magic". Magic is an item that the player may use at any time to remove large sections of the surface. If a player does not initially use their magic, any subsequent instance of obtaining magic will upgrade the magic they already possess to the next item. Each type of magic has its own pattern of removal, area of effect, and drawbacks. Magic items are ranked from the lowest level to the highest level as follows:
Firecracker: Removes one small section of pieces.
Dynamite: Removes multiple sections of pieces.
Magnet: Constantly removes pieces while it is active. The player can choose to move the cursor around during this time, allowing them to selectively remove certain sections of the sphere. The player can also keep the cursor stationary while the magnet is active to remove multiple layers of a small section of the sphere instead.
Atom: Removes the entire top layer of the sphere.
Bomb: Initially removes one section of pieces that is significantly larger in area than the firecracker. A second explosion then occurs, destroying additional pieces; its blast radius is similar to that of the firecracker.
Raygun: Similar to the magnet in its method of removing pieces, but it is much more efficient.