Tetris glossary.

No automatic falling. You move, rotate and drop each piece yourself. Stacking Lab starts at zero gravity so you can study placements without a falling timer.

A combo setup with a two-column channel. It is simple to recognize, but the next piece must still complete a row; an awkward I can interrupt the chain.

A combo setup using three open columns. The blocks left inside the channel determine which next pieces can clear a line. Width alone does not guarantee a continuing combo.

A four-column combo channel beside a built-up stack. Clear with successive pieces to extend the combo. Stacking Lab trains the right-side version: six stacking columns on the left, four combo columns on the right.

Stack six columns to one side of a one-column well and three to the other. The central well gives you surfaces on both sides for T-spin opportunities as well as four-line clears.

A one-column well separates seven stacking columns from two. This split appears in spin-stacking continuations; the narrow side needs deliberate piece management.

Each group of seven pieces contains I, J, L, O, S, T and Z once, in shuffled order. A new bag follows the previous one; two identical pieces can meet at the boundary.

Build across nine columns and leave the remaining edge column open for I pieces. Learn to keep the surface flexible without burying the well or depending on a single piece to repair it.

Gravity of twenty cells per simulation frame, making a newly spawned piece reach the stack almost immediately on a normal board. Moving across the surface and lock timing become crucial.

A half-turn made with one input. Its kick tests depend on the game; it is not equivalent to performing two 90° rotations, and standard SRS does not define a universal 180° kick table.

The piece you currently control. Once it locks, its cells join the stack and you can no longer move it. The next piece then enters, subject to the game's delays.

An opener beginning with a floating T-spin Double, often followed by a T-spin Triple and another Double. An early O helps form its base; some placements require soft drops.

Garbage attack generated per minute, not keyboard actions per minute. Whether cancelled attack is included depends on the game's statistic; compare values within the same ruleset.

Attack divided by pieces placed. It describes attack efficiency: playing faster can raise APM without improving APP. Compare matches with the same attack rules.

The pause between one piece finishing and the next becoming controllable. Some games allow movement or rotation inputs to be prepared during it. Line-clear animation may add a separate delay.

The repeat interval after DAS activates. Despite the word rate, many settings use a delay: smaller values repeat faster. In Stacking Lab, zero means instant travel to the wall or obstruction.

Ending a back-to-back chain with a non-qualifying clear. It can be the right decision when a skim or downstack saves the board. Keeping the bonus is less useful than surviving.

A chain of qualifying difficult clears, commonly Tetrises and T-spin line clears. Under common modern rules, non-clearing placements preserve it; an ordinary Single, Double or Triple breaks it. Eligibility and bonuses vary by game.

The join between two shuffled bags. Consecutive matching pieces can occur here. Tracking the boundary tells you which pieces remain guaranteed in the current seven-piece set.

Remembering which pieces have appeared in the current bag. It narrows what can arrive next, but does not reveal the exact order of unseen pieces.

A loss condition where a new piece overlaps occupied cells at spawn. It can happen before the visible board looks completely full. The exact spawn coordinates matter.

The imaginary square enclosing a piece's rotation states. A rotation can change the occupied cells inside this box; the box itself is not a solid obstacle.

A T-spin Double into T-spin Triple setup. It resembles DT Cannon with the Double section shifted sideways, but has its own construction and continuations, including routes toward C-Spin and a Perfect Clear.

A T-spin Triple followed by a T-spin Double. This is a different sequence from DT Cannon. Naming varies by community: TKI can refer to this setup in Japanese discussions.

Using generated attack to reduce pending incoming garbage before it enters your board. Any remaining attack may be sent onward. Exact timing and cancellation rules depend on the game.

A variant where unsupported blocks or connected groups fall after a clear and can trigger further clears. Ordinary row-shift Tetris does not do this.

A four-column combo channel between two side stacks. Its spawn-space behavior differs from a side channel. Stacking Lab's current 4-Wide mode uses the right edge, not this layout.

Garbage whose gaps move between rows, forcing you to navigate through multiple columns. Compare clean garbage, where several aligned gaps can be cleared together.

Several garbage rows sharing the same gap column. Once exposed, they can support a quick multi-line clear or counterattack. Keep track of where the gap changes below them.

Successive pieces each clearing at least one line. A piece that clears nothing ends the chain. It is different from B2B: an ordinary Single can continue a combo while breaking B2B.

A non-clearing placement that interrupts a combo. In Stacking Lab's 4-Wide mode, Breaks tracks early interruptions during the combo phase, not every piece placed while building the stack.

The two quarter-turn rotation directions. Learning both avoids unnecessary extra rotations. A CW kick and a CCW kick need not produce mirrored results in every situation.

The delay after holding left or right before automatic horizontal repetition starts. The first sideways step happens immediately; ARR governs subsequent repeats. Very low DAS can make unintended movement easier.

Progress toward the auto-repeat threshold. Some games preserve or let you charge it between pieces. Stacking Lab has separate options for carrying charge and resetting it when direction changes.

A short interruption of horizontal auto-repeat around certain actions, intended to reduce accidental shifts. In Stacking Lab it applies after rotation or spawn; the setting is measured in milliseconds.

A shape that strongly needs one particular piece. A deep one-column gap needs an I; several such demands at once make the stack inflexible. Prefer placements that leave multiple useful options.

Two rows removed by one placement. A T-spin Double adds spin recognition to the same two-line count.

Clearing down through an existing stack or garbage to reach lower gaps. Look at the gap below your next clear and avoid covering it with blocks that survive the clear.

A construction that resolves as a T-spin Double followed by a T-spin Triple. The initial T may be used in the structure rather than scored. Different first-bag arrangements accommodate different piece orders.

A rotation adjustment that moves a piece upward to avoid a collision. It is chosen from the rotation system's kick tests, not a separate jump button.

A connected Double-to-Double structure, commonly made by extending an existing TSD upward while waiting for the next T. Two unrelated TSDs are not automatically a Fractal. Stacking Lab builds toward this from a 6–3 foundation.

One update step in a game's timing model. At 60 updates per second, a frame is about 16.67 ms. A browser's display refresh rate and the game's simulation timing are not necessarily the same.

An opener aiming for a T-spin Triple, a Double or Single continuation, then a possible Perfect Clear. Its second-bag variations respond to piece order; a buildable start is not a guaranteed PC.

Rows added from outside your own placements, usually as an opponent's attack. They commonly contain gaps and raise the stack from below. Training and puzzle modes can also supply garbage directly.

A rule that postpones incoming garbage while you keep clearing lines. Unlike cancellation, it need not reduce the incoming amount. Rules and delay limits vary across games and rooms.

The empty cell in a typical garbage row. Downstacking means exposing and filling these gaps in a useful order; the next gap may be in a different column.

Attack waiting to enter the board. Depending on the game, you may cancel it or delay its rise with line clears. The meter is not always the amount that will rise on the very next lock.

An outline showing where the active piece would land if dropped straight down now. It previews the current path, not a strategic recommendation. The coach's suggested placement can be somewhere else.

A T-spin Single-to-Triple opener with possible Perfect Clear continuations. An early O commonly enables its base. The planned Triple must be resolved before the underlying board becomes easy to access.

Immediately drop the piece to the lowest reachable position in its column and lock it. You cannot rotate or slide it afterward; use a non-locking drop when a tuck needs another input.

Rows above the visible playfield used for spawning and high stacks. Their number and loss rules vary. A piece entering this space is not, by itself, a universal game-over condition.

Store the current piece or swap it with the stored one. In common modern rules, you must lock a piece before holding again. Hold changes the order you place pieces without changing the underlying queue.

An empty cell below occupied cells. It cannot be filled by a straight drop from above; some gaps allow a tuck or spin, while others require clearing the covering rows first.

Four blocks in a straight line. A vertical I can fill a four-cell-deep well.

Holding a piece as it spawns using an input prepared during the preceding delay. Availability and buffering behavior depend on the game; it is separate from swapping an already active piece.

A rotation applied as a piece enters, using an input prepared before spawn. It can matter at high gravity or near the ceiling. It is a rule of the game, not simply rotating quickly after spawn.

Three blocks in a row with one attached at an end. Usually blue; the mirror of L.

An ordered list of alternate positions tested when rotation would collide. The first valid position wins. A shape fitting somewhere nearby does not mean the game will choose that position.

The number of counted inputs divided by placed pieces. Lower KPP can indicate better movement efficiency, but hold, rotations, tucks and the game's input-counting convention affect comparisons.

The mirror of J: a three-block row with the fourth at the other end. Usually orange.

Completed rows disappear after a piece locks. One placement can clear several rows. Under ordinary rules, rows above them shift downward.

Extra waiting time associated with clearing rows before play resumes. It is separate from the delay after an ordinary placement. Frequent small clears can cost more time in games with a substantial clear delay.

How the board settles after rows disappear. Under ordinary row-shift rules, rows move down by the number cleared below them; unsupported blocks can remain suspended. Cascade variants use different settling behavior.

The time a grounded piece can remain controllable before it locks. Movement or rotation may reset the timer according to the rules, usually with a limit.

A loss condition involving a piece locking above the playable boundary. Some games require the entire piece to be outside; others use partial lock out. It is different from a new piece being blocked at spawn.

The maximum permitted resets of the lock timer. Once the allowance is exhausted, moving or rotating cannot postpone locking in the same way. Stacking Lab exposes this independently from lock-delay duration.

Plan for upcoming pieces while placing the current one. Start by checking whether your next two pieces still have good homes after this move, then extend the plan as recognition becomes easier.

Rows cleared per minute. It measures clearing speed, not attack output: two runs with the same LPM can send different amounts of garbage because of spins, combos and B2B.

Reflect a construction left-to-right, exchanging J with L and S with Z. Geometric symmetry does not guarantee identical spawn movement, kick behavior or build order in a particular game.

A first-bag structure with Perfect Clear and TSD continuations, often useful with early J and L. When the PC is unavailable, the remaining board supports several stacking transitions.

A lock-delay rule where successful sideways movement or rotation refreshes the timer. Most implementations limit the number of resets; compare step reset, which responds to downward progress.

Stacking Lab's opener route for a T-spin Single, Triple, then Double. Here STD names that clear sequence; it is not the same as STSD, which aims for two Doubles.

A Triple-to-Double opener with possible eight-line PC continuations and alternatives for different queues. The referenced h-docs research assumes 180° spins, so its build claims should not be applied unchanged to games without them.

A named five-bag loop aiming for TSD, TST, TSD, Tetris and a possible PC. It is not simply an updated replacement for DT Cannon; piece order can require different continuation routes.

The two-by-two square. Its outline stays the same when rotated.

Blocks extending above empty space. An overhang can enable a spin or tuck, but also blocks a straight drop. Always check how the required piece will actually enter.

A way to reason about even/odd balance in a stack or empty region. Checkerboard coloring helps test tiling possibilities; column-height parity helps explain awkward surfaces. Passing a parity check alone does not prove a solution exists.

A loss rule triggered when only part of a locked piece remains above the boundary. Not every game uses it; compare ordinary lock out and block out before assuming touching the top always ends a run.

The share of piece orders that admit a Perfect Clear under stated assumptions. Hold, visible previews, rotation rules, known solutions and incoming garbage all matter. A published percentage is not an unconditional success rate.

A line clear leaving no locked blocks anywhere on the board. It can use one or several clearing rows; four lines cleared is not automatically a PC. Bonuses depend on the game.

A starting construction aimed at a four-line Perfect Clear. Its finishing pieces depend on the second bag and hold. If the finish is unavailable, switch to a continuation instead of forcing an impossible empty board.

Pieces placed divided by elapsed seconds. It measures speed, not placement quality. A slower run with cleaner decisions can beat a faster run that creates holes.

How many upcoming pieces are visible in Next. More previews offer more planning information; they do not change the piece sequence itself.

The ordered pieces coming after the active one. The preview shows a limited portion of that sequence. Hold offers one extra piece choice; it does not let you pick any future piece.

Blocks left in the combo channel after a clear. A common 4-Wide pattern keeps three residual blocks: placing four new blocks and clearing a four-cell channel row preserves that count. Their arrangement still matters.

The reference point around which a piece's orientation changes. Combined with the kick rules, it explains why a visually symmetric shape can land differently after opposite rotations.

The current orientation of a piece. SRS labels states 0, R, 2 and L. Even pieces with repeated outlines can occupy different cells within their rotation box.

Two offset pairs forming an S-shaped zigzag. Usually green; the mirror of Z.

The soft-drop speed setting. Stacking Lab uses zero to mean infinite, giving an instant non-locking descent. Other games may label infinity differently or calculate the factor against a different speed baseline.

An opener linking a T-spin Single, a Double and a possible Perfect Clear, sometimes with another Single in the finish. When the PC is unavailable, the post-Double board can transition to ordinary stacking.

A combo channel along an edge, with the six-column stack on the other side. Stacking Lab uses the right-hand channel. Unlike center 4-Wide, the tall stack occupies the middle spawn area.

One row removed by a placement. A Single can extend a combo or repair the surface; an ordinary non-spin Single commonly breaks B2B.

Clearing small numbers of rows from the surface to lower or reshape the stack. Useful when waiting for an I would create too much risk. It may sacrifice B2B to restore a playable board.

Move the active piece downward faster while retaining control, subject to the game's landing rules. Use it to reach the entry height for a tuck or spin before locking.

Garbage without a usable gap, often added as a survival timer or room rule. It cannot be cleared like ordinary single-hole garbage, so it permanently reduces usable space under those rules.

Drop instantly to the landing surface without immediately locking. You can then rotate or slide if the rules and remaining lock time allow it. It is not the same as hard drop.

Where and how a new piece enters the board. Spawn heights vary between games, even among SRS games. A clear-looking visible board can still have a blocked spawn area.

A large amount of attack delivered over a short period, often by chaining strong clears. Timing it when the opponent cannot cancel or downstack can matter as much as its size.

A lock-delay rule that refreshes the timer when a piece descends to a lower row. Sideways motion alone does not provide the same reset as in a move-reset system.

A continuation related to SDPC that goes from T-spin Single to Double to Triple instead of committing to the PC route. Recognize the branching point rather than treating it as an unrelated first bag.

One connected structure that yields two T-spin Doubles. Often recognized through a three-by-three empty region with J/L construction. It is a distinct geometry from Fractal, not a name for any two consecutive TSDs.

The heights and shapes at the top of your stack. A useful surface accepts several upcoming pieces; a completely flat surface is not always the best fit for the actual queue.

Three blocks in a row with one attached in the middle. Commonly purple.

A cavity intended for a T piece. A T fitting inside does not automatically earn a spin: the entry, final action and occupied corners must satisfy the game's detection rules.

A recognized T-spin that clears two rows. It combines spin detection with a two-line clear; its attack and score are game-specific. The interactive example shows the rotation, locked position and resulting board.

A recognized T-spin that clears no rows. Some games award points, but it is not automatically an attack or a line-clear bonus. Non-clearing placements usually preserve rather than extend B2B.

Four rows cleared by one placement, normally using a vertical I. The name also refers to the game itself. A Tetris can leave many blocks behind, while a Perfect Clear leaves none.

The fraction of cleared lines that came from four-line clears. It describes scoring style in classic play; a high rate is useful only if the stack remains survivable.

A shape made from four edge-connected squares. Tetris uses seven one-sided shapes: I, J, L, O, S, T and Z. Letter names avoid confusion when different games use different colors.

A common T-spin test: at least three diagonal cells around the T's pivot are occupied, together with the required final rotation. Corner orientation and the kick used can determine full versus Mini classification.

A first-bag TSD opener commonly enabled by an early I. It leaves a low board with flexible continuations. Here TKI means the opening Double; some communities use the same name for C-Spin.

Losing because of a height-related rule, such as a blocked spawn or an out-of-bounds lock. The visible top edge alone is not a universal test. Learn the selected game's actual loss conditions.

Three rows cleared by one placement. An ordinary Triple differs from a T-spin Triple; equal line counts do not imply equal score or attack.