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Lizely

LITS Puzzle

Shade one valid L, I, T, or S tetromino per region while preserving one connected, square-free network.

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How to use

  1. 1.Move with the arrow keys and press Space to shade cells; Enter adds an optional empty mark.
  2. 2.Place exactly four cells in each bold region so they form an L, I, T, or S tetromino.
  3. 3.Connect all shaded cells, avoid filled 2×2 blocks, and never let matching shape types touch by an edge.

About LITS Puzzle

LITS Puzzle is a four by five tetromino-placement logic game based on Nikoli's original puzzle. The board is divided into two bold-bordered vertical regions. Shade exactly four connected cells in each region so those cells form one of the four permitted tetromino types: L, I, T, or S. The O square is excluded by the global rule against a fully shaded two by two block.

Nikoli provides the primary publisher definition, and Puzzle LITS independently cross-checks all four constraints, including how rotations and reflections count as the same shape type. The small two-region board, selected shapes, controls, status display, and score are Lizely product choices. It is fixed rather than generated so the complete keyboard route is reproducible.

Move with the arrow keys. Press Space to shade or unshade the current square. Press Enter to place or remove an optional empty mark on an unshaded square. Mouse and touch users can click for shading and use the context-menu gesture for an empty mark. Notes do not affect validation or score.

Region A contains the first two columns. Its disclosed solution is a vertical I tetromino in the second column at zero-based cells 1, 6, 11, and 16. Region B occupies the remaining three columns. Its solution is a T tetromino at cells 7, 8, 9, and 13: a three-cell horizontal bar with a centered stem below.

The two shapes share an edge between cells 6 and 7, which connects all eight shaded cells into one orthogonal network. Their types differ, so the adjacency is legal. The arrangement contains no filled two by two block. Eight correct shade actions complete the board and score 920 from a starting score of 1,000.

Validation recognizes shapes independently of position, rotation, or reflection. Coordinates are normalized and compared with generated variants of the four permitted bases. A region with more than four shaded cells is contradictory. Four cells that do not form L, I, T, or S are contradictory. Any fully shaded two by two area is rejected immediately.

When both regions hold recognized shapes, touching shapes of the same normalized type are rejected even if one is rotated or reflected. Once both regions contain four cells, the browser also proves that all eight shaded squares are connected by an orthogonal breadth-first traversal. Two valid but separated tetrominoes therefore cannot be celebrated as a solution.

The independent tests identify I, L, T, and S directly, verify four shaded cells per region, global connectivity, the two by two prohibition, and different touching types. Adversarial cases cover a filled square block, two touching vertical I pieces, and two separated valid I pieces. The completion simulation shades all eight disclosed cells and asserts the 920 score.

The interface uses semantic CSS-grid buttons and site variables, not canvas pixels or downloaded art. Every cell announces its row, column, region, shade, mark, and keyboard-selection state. There is no random service, timer, audio, account, hardware dependency, or pointer-only gesture.

Restart clears shades and notes and restores the first cell and 1,000 points. Best score stays only in localStorage. Double-press Escape for the shared spreadsheet boss cover and repeat it to return to the same board. For more region and shading logic, try Mosaic, Heyawake, Hitori, or Stitches.

Methodology & sources

The validator groups shaded cells by the two declared regions. Four-cell coordinate sets are normalized across eight rotation/reflection transforms and compared with I, L, T, and S bases. It scans every 2×2 window, checks cross-region touching types, and breadth-first traverses all shaded cells. Completion requires [4,4] cells, valid different touching shapes, no 2×2, and one connected network. Score is max(0, 1000 − 10×shade actions).

Frequently asked questions

Why is the O tetromino not allowed?
It is a filled two by two square, which directly violates a global LITS rule.
Do rotated shapes count as different types?
No. Rotations and reflections remain the same L, I, T, or S type for the touching-shape rule.
Must shaded cells connect across region borders?
Yes. All shaded cells on the whole board must form one orthogonally connected network.
Do empty marks affect completion?
No. They are reasoning notes only; shaded cells determine shapes, connectivity, contradictions, and score.

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