Line clear

The object of Tetris is to last as long as possible before the screen fills up with tetrominoes. To do this, you must assemble the tetrominoes to form one or more rows of blocks that span the entire playing field, called a line clear. When you do so, the row will disappear, causing the ones above it to settle.

Types of line clears

Single

A single is the act of clearing one line at a time:

Double

A double is when two lines are cleared at once:

Triple

A triple is three lines cleared simultaneously. Most games allow only I, L, and J tetrominoes to complete a triple, but newer games with SRS allow S, Z, and T tetrominoes to twist into seemingly impossible positions.

Tetris

A tetris is four lines cleared simultaneously. In most games, this can only be done with an "I" tetromino.

Hurdle or Split

In Tetris DS's mission mode, the act of clearing two or three lines separated by one or more rows with gaps is called a hurdle. In Sega Tetris, this move was called a Split(separated double) or One-Two(separated triple) and these launched a special attack in VS mode, and any tetromino that can complete a triple can complete a hurdle:

Back-to-Back

Main Article:
Back-to-Back

Combo

A combo refers to either of the following:

• Making a line clear with one piece and sequentially making another clear with the next piece, and so on. (e.g. SRS games, such as Tetris Online Japan)
• Making a line clear with one piece, and making another line clear before some arbitrary timer expires. (e.g. Cultris)

In some cases, drilling through garbage or skimming is likely to produce combos. Not all games reward combos; those that do include the following:

• TGM series
• Magical Tetris Challenge
• Cultris
• Tetris Evolution (two of the achievements relate to back-to-back Tetris combos)
• Tetris Party
• Tetramino (NES)

Line clear gravity

After a line clear, the blocks above the line move down. How they move down depends on the game. Some systems allow for "recursive gravity" that clears more than four lines with one piece.

Naive

Most tetromino based games use naive gravity. Here, the blocks above a cleared line move down by exactly the number of cleared lines below them. This can often leave floating blocks, unconnected to anything, after a line is cleared.

Drop J

Line clear

Naive gravity

Sticky

The playfield is divided into connected segments using flood fill. Any blocks that are adjacent horizontally or vertically are marked as one segment, that is, they are treated as having "stuck" together. Each segment falls independently until it meets the floor or another block. Additional line clears may result.

Drop J	Line clear	Mark segments	Segment lands	Segment lands
Line clear #2	Mark segments	Segment lands

Games that use sticky gravity:

• Super Scope 6 Blastris A
• Tetris Blast and Bombliss
• The Next Tetris (modifies rule such that only blocks of a single color can form a segment)
  • Re-released as Tetris Worlds Sticky
• Lockjaw: The Overdose

Cascade

When each piece locks, its connections to other blocks in the piece are stored. After lines are cleared, each piece is marked as a separate segment, and then each segment falls independently until it meets the floor or another block, as in Sticky. Games that use cascade gravity:

• Tetris 2 (Tetris Flash)
• Tetris 64 Giga mode
• Quadra
• Tetris Worlds Cascade and Fusion
• Tetris DS Touch
• Tetris Friends Rally 8P

Non-tetromino games:

• Dr. Mario
• Super Puzzle Fighter II Turbo

Delay

Some games impose a line clear delay after each piece that completes one or more lines and/or a line gravity delay every time blocks move down by one row. For example, Tetris The Grand Master and Tetris DS wait 400–700 ms. In games with a large line clear delay and scoring based on play time, it is to the player's advantage to make multiple lines at once (triple or tetris) so that less time is spent in line clear delay.

See Also

• Twist
• Back to Back T-Spin Triple