Released exclusively on the Nintendo 64, this game is almost entirely different from the standard Tetris formula. It started out as an Atari Jaguar game titled Phear, on display at CES '95. Nintendo bought the rights to the game from its developer, and released it two years later as Tetrisphere.
Instead of starting with an empty playfield and placing pieces, each level consists of a core surrounded by layers of pieces. Although the game's playfield appears to be a sphere, it is actually a 32x32 square grid, with the west and east sides connected and the north and south sides connected. No matter which direction the player moves around the field, the pieces remain in the same orientation.
The objective in most game modes is to clear pieces from each layer of the game field, exposing enough of the core to free the robot trapped inside. This is accomplished by dropping pieces to form a group of three or more of the same type, to clear those and any other identical pieces touching the first group. The cursor shows where the current piece will be placed, and this cursor can be moved around with the digital control pad. The cursor will turn bright if placing the piece will start a reaction. Pieces are placed by pressing the A button, and it is possible to slide pieces of the same type as the current piece by moving the cursor over them and holding B. When holding B over a movable piece, the control pad can be used to move the piece. A piece preview on the lower left corner of the screen shows the piece currently held, as well as the next two pieces.
The player has three lives to complete each level. Placing a piece where it will not start a reaction takes away one life. If a piece is on a high enough layer that it flashes red, then placing a piece on it will also take away a life, even if normally it would start a reaction. There is also a multi-colored timer, which ticks down when the player is not clearing pieces. If the blue timer runs out, the yellow timer will start ticking, and the camera will slowly zoom towards the field. If it hits the field, the player loses a life.
For each game mode, the player can select one of several characters to play as. Each character has two statistics, both of which influence the auto-repeat rate of cursor movement under different conditions. Speed determines how fast the cursor will move normally, and Power determines how fast it will move when sliding a piece. This does not limit how rapidly the player can tap the control pad to move the cursor, however.
There are six types of pieces in total, and any gaps between pieces on the field are initially filled by 1x1 crystal pieces. Usually, levels don't use all six types of pieces at the same time. Crystal pieces can be broken by sliding other pieces into them, or clearing other pieces next to them. Blue O pieces must be placed at 90-degree angles in order to be cleared together. This also applies to the green I pieces, and the yellow horizontal I pieces, both of which are only three blocks long. Red T pieces, cyan Z pieces, and small pink L pieces need only touch each other at any edge to be cleared together. Two or more pieces on adjacent layers must be exactly on top of each other to be cleared together. Sometimes the player will receive a wild card piece. This piece can be dropped as any type of piece, and can be used to slide any piece on the field.
Power Pieces and Special Combos
Every time pieces are cleared from the field, certain remaining pieces will be transformed into glowing Power Pieces. These can slide up over other pieces, one layer at a time. Also, clearing a Power Piece replenishes the timer greatly, and reactions started with a Power Piece take longer to clear than normal reactions, which makes it easier to start another combo while the first is still clearing. Specifically, every time 19 or fewer pieces are cleared, that same number of sparks fall to the field, and each one that touches a normal piece transforms it into a Power Piece. A spark will have no effect if it touches a Power Piece, the core of the field, or a crystal piece. The player can move the cursor to loosely determine where the sparks will land. A Power Piece can be obtained without having to clear pieces by moving the cursor over a like-shaped formation of crystal pieces, and pressing B.
Two types of special combos can increase the player's X count, which acts as a multiplier to points earned from clearing pieces. A Gravity Combo can be executed by causing one piece to fall and form a group, by either clearing or sliding a piece that is holding it up. A Fuse Combo can be executed by starting a reaction with a Power Piece, then grabbing one of the flashing pieces (referred to as a Fuse) with B before it gets cleared, and sliding it to another group.
If a combo of 20 or more pieces is cleared, the player receives a Magic power-up. If the player already has Magic, it is upgraded to the next level. A bar underneath the combo counter also fills up as pieces are cleared, and will give the player a Magic power-up when it is filled completely. Magic can be used to clear pieces and reach the core quickly. Sometimes a 1x1 magic crystal can be found on the game field, and it will give the player Magic or upgrade their current one if broken open. The Rocket will clear a small area on the top layer. The Dynamite splits into five pieces to cover a wider area than the Rocket. The Magnet rapidly zaps away pieces over the spot that is targeted. The Molecule will remove the entire top layer of pieces from the field. The Atom Bomb creates a deeper explosion that reaches through multiple layers. The Laser acts like a much more powerful version of the Magnet.
Practice Mode can be selected from the main menu. In this mode, the player can set up a level with any of the six piece types (at least two must be selected), 2 to 5 layers of pieces, and a requirement to expose anywhere from 1 to 99 sections of the core to clear the level. In Practice Mode, there is no time limit.
Rescue is the basic game mode, in which the player clears levels by exposing the core of each one to free the robots trapped inside them.
Hide and Seek is an objective-based game mode, with varying levels:
- Multi - Players must expose one of the images at the core to clear the level.
- Drill - There are five drills on the outer layer, with an image at the bottom of one of the drills. Players must find and expose the image to clear the level.
- Unique - One drill indicates where an image is at the core, but unlike most levels, the image varies in shape and size.
- Shift - Four pieces are located under drills. Players must expose the pieces and rearrange them to form a 16x16 image. Note that this level will always use the blue O piece.
- Connect - A drill indicates the start of a series of images at the core. Players must expose these images, usually by following the lines connecting them.
- Brick - Bricks shaped like a double-mirrored pink L piece are dotted along the sphere. Players must have one of these bricks reach the core by moving and clearing pieces around it.
- Tower - A plus-shaped tower is located on the sphere. Players must expose the space around the tower to finish the level.
- Crystal Tower - A variant of Tower, only the tower is now breakable by moving pieces into the tower or breaking blocks next to it. Damaging the tower results in an automatic game over.
- Hide and Seek - Played the same as Rescue. Hide and Seek is always the last level of a set.
In Time Trial mode, the idea is to go through stages as fast as possible, earning points and clearing stages until the timer reaches zero.
In Puzzle mode, each level has a configuration of pieces, and the player must clear them all, using a given number of slides and drops. There is no time limit, and every piece is a wild card piece. The camera can also be zoomed in and out by pressing L and R, to aid in determining the layout of pieces. A puzzle can be restarted with C-up if you make a mistake.
In Vs. Mode, the player can compete against either another player or the CPU, trying to reach the core of their gamefield first. When enough pieces are cleared, dark pieces will be sent to the opponent's field. These cannot be cleared directly, but must be cleared by adjacent pieces. Each round ends when one player exposes enough sections of their core, or loses all three of their lives. Increasing the X Count multiplier boosts the amount of dark pieces sent to the opponent.