Every placement in Block Stacking Puzzle must satisfy four conditions at once — staying inside the 5×5 workbench, not overlapping a previous voxel, sitting on the floor or directly on another filled cell, and committing as one atomic change — before the engine will move a single voxel onto the board.
That single sentence holds the entire placement rule set. The game opens a small inventory of labeled pieces, each described by relative voxel coordinates, and the player rotates each piece through quarter turns and chooses its lower-left origin on a fixed 5×5 board. The intent is not to clear a row, time a falling piece, or stack until a slab lands — it is to use every finite piece so the final occupied set equals a target silhouette exactly, with no overlap, no overhang, no gap, and no unsupported voxel. Because the rules can be stated plainly, this guide walks through each condition in the order the engine actually evaluates them, then shows how Check shape, Undo, and the two-mismatch limit turn those rules into a workable 1,000-point finish on five original targets.
The Four Conditions Every Placement Must Meet
The placement engine tests four independent conditions before any voxel changes state, and every one of them must pass simultaneously.
| Condition | What it means in plain terms | What happens on failure |
|---|---|---|
| In bounds | Every transformed cell lies inside the 5×5 board. | The whole piece is rejected and the inventory is unchanged. |
| Unoccupied | No transformed cell overlaps a previously placed voxel. | The whole piece is rejected; nothing partial appears. |
| Ground or supported | Every raised cell has another occupied voxel directly beneath it. | The whole piece is rejected, even if every other condition holds. |
| Atomic commit | All four checks evaluate first; the visible state changes only after they all pass. | Rejection is a single all-or-nothing event, not a partial placement. |
This collection of conditions is what makes the Block Stacking Puzzle rules feel strict and predictable. There is no halfway state: the piece either lands whole or leaves the board exactly as it was.
How to Place a Piece Step-by-Step
The placement rule is mechanical, and the full sequence fits a short list. Follow these steps for each piece you intend to commit.
- Select an unused lettered piece from the inventory and read its relative voxel coordinates shown beside the piece button.
- Press Rotate until the piece's shape lines up with the plan you have in mind for the target silhouette.
- Choose the lower-left origin cell on the 5×5 workbench where the whole piece should anchor.
- Watch the engine test all four conditions at once; if every voxel is in bounds, unoccupied, and supported, the piece lands as one unit.
- If the condition set fails, the board is unchanged — use Undo to recover any earlier placement you want to revise, then try a different rotation or origin.
- Press Check shape only when the occupied cells exactly match the target set; a perfect match adds 200 points and unlocks the next level.
The Direct Support Rule Explained
Direct support is the condition most newcomers misread, because the word "support" suggests physics. In this puzzle it is an abstract rule with a precise definition: a raised cell is legal if and only if the cell directly beneath it is already occupied when the new piece is committed. Empty air, a diagonally adjacent voxel, and a removed voxel that has been undone do not count as support.
The rule has a useful corollary: cells within the same piece can support one another. A vertical bar can therefore be placed on the floor in a single atomic placement, because every cell above ground inside the bar rests on the cell below it inside the same bar. This is why tall placements are not impossible — they only need a continuous support chain down to the floor that is internal to at least one piece.
It is worth stating what the rule is not. The engine does not claim a physical load limit, structural engineering property, material strength, gravity measurement, or external packing standard. The plus signs visible on the board describe only the target occupancy; they do not assign a piece, orientation, origin, or build order to any target cell.
Rotation, Origin, and How Pieces Are Defined
Every piece in the inventory is a small cluster of voxels stored as relative coordinates normalized to four quarter-turn orientations. The visible piece button shows the current normalized shape so the available geometry is readable without a hidden preview; there is no private data attribute carrying solution hints. When the player presses Rotate, the piece's cells turn around its own internal reference frame in 90-degree steps and the displayed coordinates update with it.
The origin is always the lower-left cell of the rotated piece's bounding box, projected onto a chosen cell of the 5×5 workbench. Choosing the origin is therefore choosing a single anchor point; the rest of the piece follows by translation. This makes four questions concrete for every attempt: which piece, which orientation, which origin, and whether the four placement conditions all hold.
Pieces behave like atomic voxels relative to the engine, even when the piece is shaped like an L, a T, or a flat deck. Long horizontal pieces often form useful bridges only after their entire span has support, and vertical placements can establish a column in one atomic commit because their internal cells self-support. The placement rule is the same for every shape: the whole shape lands together or not at all.
Validation, Undo, and the Two-Mismatch Rule
Check shape runs a pure final validation against the target set rather than a piecemeal score. The occupied list must share its volume exactly with the target volume, contain no duplicate cell, include every target coordinate, include no coordinate outside the target, and remain directly supported under the same rule used during placement. When all of those checks pass simultaneously, the level grants exactly 200 points and unlocks the next original target.
Two repair mechanics keep the run from ending unfairly. First, Undo removes the most recent whole-piece placement, returns that piece to the available inventory, and preserves earlier legal work — players can rebuild a level around any prior correct state without restart penalty. Second, pressing Check on the identical layout again is deduplicated, so a double press does not consume a second mistake; only a second genuinely different mismatched layout closes the run.
When a corrected layout succeeds after one failed check, the failure history clears before the next level begins. Restart reconstructs the exact opening state of level one, which makes it safe to abandon a stuck attempt and start fresh without losing access to later levels you have already completed. Independent verifiers replay the public state transitions to confirm that atomic invalid actions, Undo, Restart equality, boundary rejection, overlap rejection, support rejection, terminal freezing, repair after one mismatch, deduplication, and second-layout deadlock all behave as the rules describe.
Scoring, the Five Original Levels, and the 1,000-Point Finish
The scoring rule is the simplest part of the rule set. Each level's exact occupancy match awards exactly 200 points. Five matched shapes produce the exact maximum score of 1,000, and there is no partial credit for matching only part of a target. The five levels move from a square foundation to a tall step, a low ledge, a two-deck rectangle, and a final staircase; every level is balanced exactly, so the total cells in the finite piece inventory always equal the target volume for that level.
Not every target has a single legal arrangement. The independently verified complete solution counts across the five levels are 4, 1, 1, 2, and 4. Some targets admit one piece assignment, while others intentionally allow several equivalent assignments or orientations. An independent exhaustive oracle enumerates every rotation, every in-target origin, rejects overlap and unsupported final occupancy, verifies that some sequential build order is legal, and locks those counts; the product does not pretend the multi-solution levels are unique. Any legal arrangement that produces the exact supported target occupancy is accepted.
How Block Stacking Puzzle Differs From Tetris 3D and Tower Stack
Several casual-stacking games share vocabulary with this one, but their rules diverge sharply from the placement and validation rules above. The table below sets out the rule gaps the product contract explicitly defines, so a reader coming from another block game can see exactly which mechanics do not transfer.
| Rule area | Block Stacking Puzzle | Tetris 3D | Tower Stack |
|---|---|---|---|
| Core objective | Match the target silhouette exactly with finite pieces. | Hard-drop pieces to clear complete 3D layers. | Time a moving slab onto progressively narrower landings. |
| Piece supply | Finite labeled inventory; no falling stream. | Falling piece stream. | Moving slab driven by a timing window. |
| Placement rule | Atomic: in-bounds, unoccupied, ground or supported. | Hard-drop rules with line clears. | Overlap clipping with horizontal crop and overhang score. |
| Completion check | Exact occupancy equals target set; 200 points per match. | Layers disappear when complete. | Overhang scoring with a timing window. |
| Failure limit | Two genuinely different mismatched checks close the run. | Layer-clear failure conditions. | Timing-window failure conditions. |
Because the rules for Block Stacking Puzzle reduce to a fixed inventory, atomic placement, and exact-set validation, the only variables a player controls are which piece to use, its quarter-turn rotation, and its lower-left origin; the rest is arithmetic against the target. Readers who want a parallel rules walkthrough in another puzzle family can compare the structure with Hitori Puzzle rules explained in a complete walkthrough, which uses the same "every move has a precise condition" framing in a different domain.