Tetrisphere

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.

Gameplay
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 stack of eight 32x32 square grids, with the north/south and east/west sides wrapped. 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. Moving the cursor over a piece of the same type held and holding B allows the piece to be dragged. 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 drop is attempted on layer eight, then the player loses a life instead, 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 the timer drains to red, the camera will rapidly zoom into the sphere. If the camera reaches where a piece is (or layer one otherwise), the piece in hand is automatically dropped, and the player loses a life if this does not start a chain. The timer freezes and the camera zooms out to its furthest while pieces are clearing or Magic is being used.

For each game mode, the player can select one of seven robots to play as. Each robot has a speed and power level, both of which determine 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. These stats do not influence how the cursor moves when the control pad is manually tapped.

Pieces
There are six types of pieces in total, and any gaps between pieces on the field are initially filled by 1x1 crystal blocks and magic blocks. Usually, levels don't use all six types of pieces at the same time. Crystal/magic blocks can be broken by sliding other pieces into them, or clearing other pieces next to them. For tetromino/trimino pieces, "next to" means that their edges must match. That means that the I and O pieces don't match if they're offset at all. The game is more lenient with the T, Z and L pieces due to their irregular shape (even the two-block-side of the Z piece can be offset in either direction). Above each other, though, pieces must be exactly overlaid. Pieces always have the same orientation. There are three tetrominos: blue O pieces, red T pieces and cyan Z pieces. There are three triminos, green longitudinal I, yellow latitudinal I, and a pink three-block-corner, sort of like a truncated L. 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 nineteen or less pieces are cleared in a combo from the field, an equivalent number of sparks rain onto the screen. Where these sparks hit a normal piece or dark piece, said piece turns into a Power 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. With a wild card piece, holding a piece with B and rapidly moving away results in dragging the piece's shadow. Moving this shadow over a suitable area of crystal blocks also forms a Power Piece.

Power Pieces return a time bonus to the timer however they are cleared. They can also be dragged up layers, one layer at a time. A chain started with a Power Piece executes more slowly than a normal combo, and each piece individually checks if their are like pieces beside or beneath it to clear. Every Power Piece chain within the same combo slows down the speed at which the chain clears pieces.

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 Power Piece chain, and then grabbing one of the flashing pieces (referred to as a Fuse) with B before it gets cleared and releasing it by two or more of the same piece type. Fuses may de dragged up layers, as a Power Piece would. Both types of special combos are considered normal chains, except for Gravity Combos that result from cascades as a consequence of pieces clearing. The X count can be increased a maximum of ten times with each type of combo, to an overall maximum of 20x (ten Fuse and nine Gravity Combos, or vice versa.)

Hybrid Combos
A Fuse Combo only requires a glowing piece held by the B button to be released next to a suitable amount of pieces; as a consequence, one can start a Power Piece combo, then immediately grab the next piece and release it to earn a Fuse Combo on the pieces that would have inevitably cleared anyway.

The piece that falls to initiate a Gravity Combo itself can be grabbed and moved as a Fuse. If a Gravity Combo is started, and the piece that dropped is immediately grabbed and released, as with the above technique, the player will receive the benefits of performing both the Gravity and Fuse Combos. This hybrid combo thus earns two levels of X Count (one for each category) and fills six bars of the Magic Meter, making it extremely efficient.

Magic
Magic can be obtained one of three ways: by clearing glowing magic blocks, which have the same properties of crystal blocks; by clearing a combo of 20 or more; or by filling the Magic Meter above the timer to the 14th bar (single player) or ninth bar (multiplayer). The Magic Meter increments by one level with every combo of 6 or more, and by 3 levels with each fuse or gravity combo. There are six levels of Magic. The Firecracker clears all uncovered pieces in a small area. The Bundle 'O Dynamite splits into five pieces to cover a wider area than the Firecracker. The Electro-Magnet slowly pulls away pieces, and is directed by the cursor. The Atom removes all uncovered pieces on the playing field. The Bomb clears all uncovered pieces in a massive area, and then clears a small area of uncovered pieces at its epicenter. The Ray Gun operates like the Electro-Magnet, but has a larger area of effect. In multiplayer, only the Bomb (with the effect of the Firecracker) is available. Obtaining a Magic when the player already has one upgrades it to the next level, if possible, going from Firecracker to Ray Gun. Losing a life destroys whatever Magic the player is currently holding.

Game Modes
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 similar to Rescue, but each stage can have one of eight objectives assigned to it, all of which involve some variation of clearing pieces from a suitable area of the core.

In Time Trial mode, the player is given five minutes to score as many points as possible.

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 (although time taken is tracked for the entire mode) 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 Lines mode (enabled for single player and multiplayer by entering LINES as your name), 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. This code must be reentered every game session.

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 dropped on top of, but must be cleared through a combo including them, or via Magic. Each round ends when one player exposes enough sections of their core, or loses all three of their lives.

Dark Pieces and Garbage
Garbage about to be sent is tallied by dots and squares in the middle of the split-screen division. Dots represent pieces that will turn to dark pieces, and squares dark pieces sent to drop on the opposing gamefield. Garbage is earned by clearing combos of four or more, with each piece after the third earning a dark piece. The player's current X count grants an equivalent garbage bonus for each attack, and clearing dark pieces earns the same amount of garbage to be sent. Dots collapse into squares, and squares into larger squares, at certain thresholds of garbage. Eight dots condense into a small square, and two small squares and six dots condense into a medium square. Large squares bear ominous, leering eyes.

There is a rudimentary system for cancelling garbage when it is being earned on one side. Additionally, dark pieces that are earned too late to be sent with the attack they are associated with are "saved" and sent with the next combo a player does.

Scoring
Score is technically a component of all game modes, but is only tracked in a high score table for Rescue, Hide & Seek and Time Trial.

The starting value for each piece as it is cleared is 100 for a normal piece, and 1000 for a Power Piece. These values are multiplied for each Power Piece cleared within a Power Piece chain in the combo, inclusive. For example, dropping a piece on a Power Piece which then clears two normal pieces grants a base score of 3400: 1000 for the initial drop (a piece dropped on a Power Piece counts itself as a Power Piece), 2000 for the second Power Piece, and then 200 each for the two normal pieces. This score is then multiplied by the player's X count. Strangely, the piece that initiates a Fuse combo does not return points at all.

A score bonus of 1000 is given when a Power Piece is created on crystal blocks (unaffected by X count). A bonus of 10,000 (affected by X count) is given whenever a portion of the 2x2 pattern tessellating the first layer of the gamefield is exposed.