Rules
LITS is a shading puzzle. The board is a square grid. Thick lines are the borders of the regions. Thin lines are the cells inside a region. Each region is a group of cells that share sides, and each region holds exactly four shaded cells. Those four cells form one tetromino: an L, an I, a T, or an S. An L is three cells in a line with one cell beside an end, and the J turn is the same shape. An I is four cells in a straight line. A T is three cells in a line with one cell beside the middle. An S is a zigzag of four cells, and the Z turn is the same shape. A square of four cells is not a piece. Two pieces of the same shape must not share a side. Pieces of different shapes may share a side, and the same shape may touch at a corner. The shaded cells of the whole board share sides in one group. A fully shaded 2×2 is not allowed, even across a border. You shade a cell, or you mark it with a dot when you already know it is empty. Dots are optional. The puzzle is finished when the shaded cells are that one set, even if some empty cells are still blank. Finished pieces are not labelled. Play is 5×5 easy and medium, 6×6 medium, and 8×8 easy and medium. The daily puzzle is a 6×6 medium grid. People also look this up as nuruomino.
Nurikabe also shades a group that shares sides and refuses a 2×2. There, three black cells of a 2×2 force the fourth to stay white, and the black cells are one sea. Here, three shaded cells of a 2×2 force the fourth to stay empty, and the shaded cells are tetrominoes in one group.
- Thick lines are regions. The board is a square grid. Thick lines are the borders of the regions. Thin lines are the cells inside a region.
- Four cells, one tetromino. Each region holds exactly four shaded cells, in an L, an I, a T, or an S. A square of four cells is not a piece.
- One group, and no 2×2. Pieces of the same shape must not share a side. The shaded cells of the whole board share sides in one group, and a 2×2 is never fully shaded.
- Dots are optional. A dot is a cell you already know is empty. The puzzle is finished when the shaded cells are that one set, even if some empty cells are still blank.
This finished grid has an S, two L pieces, and an I. It has no T. The T is still a piece you will meet. A later grid opens by shading one. Empty cells stay paper. The frame is the solved frame. The shades are the solved teal. Region borders are teal. No dots. No yellow ring. No letters on the pieces. A printed answer fills the shaded cells and leaves empty cells blank. Dots are not printed. Pieces are not lettered.
- Shade
- Dot
- Region border
- Broken shade
Choose Shade or Dot under the board. Tap a cell, or drag across cells, to place that mark. Tap a cell that already has the mark to clear it. A cell with the other mark takes the new one when you tap it. A drag follows the first cell: it places the mark, or it clears when that cell already has it. With a mouse, right-click places a dot, or clears a dot that is already there. Arrow keys move and stop at the edge. The first arrow, when nothing is selected, selects the top-left cell. Space or Enter places the selected mark, or clears it when the cell already has that mark. S or 1 shades. X, D, E, or 2 places a dot. M switches Shade and Dot. Backspace, Delete, or 0 clears the cell. There is no cycle through the marks.
While the puzzle is unfinished, the line under the board reads: "Tap or drag to mark. Tap again to clear. M switches mode."
Press Hint for one step the rules already force, with a sentence saying why. Hint lights the cells it writes. Press Check when you want the board checked. A legal unfinished board gets "No mistakes so far. Keep going!" A broken board gets "A region has the wrong shaded shape, two matching shapes touch, a 2×2 block is shaded, or the shaded cells are split. Look for the marked cells." Hint on a broken board gets "This board has a mistake, so there is no hint yet." If Hint finds nothing on a legal board, it says "No forced cell from here. A shaded cell or a dot may be in the wrong place, so try Check or Undo." Undo and Redo step through the moves. Reset clears every shade and every dot you placed. The regions stay. When the shaded cells are the unique set, the board turns teal. The dialog title is "Solved!" The dialog body is "One tetromino per region, all shaded cells joined, no 2×2 shaded block." The Mistakes counter counts how many times Check found a broken board. It is not a score.
The ideas, in the order you can use them, are these. Three cells of a 2×2 are shaded, so the last cell stays empty. Every way to place this region's tetromino covers these cells, or none of them do. Only some placements still fit beside the neighbouring regions. Medium grids then keep the shaded cells in one group: a cell every remaining placement needs is shaded, and a cell none of them use stays empty. The button writes one of those ideas and stops. A press that writes both a shade and a dot has its own sentence, so it has its own section below. On that press the line under the board still names one cell, the first cell in the write. A blank grid has no three shades yet, so it opens on the region's own placements. The square is still the first idea to learn.
A cell turns coral when a region has too many shaded cells, too few cells left to reach four, four shaded cells that are not a tetromino, a 2×2 block is shaded, two pieces of the same shape share a side, or the shaded cells are split into more than one group. With error highlighting off, none of that coral is drawn. The picture of a finished grid in this article leaves the empty cells blank. A printed answer does the same. Dots are not printed. Pieces are not lettered.
- Undo
- Redo
- Reset
- Hint
- Check
The square
Three cells of a 2×2 are shaded, so the last cell stays empty. The square can cross a region border. A blank grid has no three shades yet, so it does not open here.
No square Easy
When three cells of a 2×2 are shaded, the fourth stays empty. You do not choose a shape for it. On this grid row 4 column 1, row 5 column 1, and row 5 column 2 are already shaded. They are three cells of the L in the bottom-left region. Row 4 column 2 is the fourth cell of that square, and it sits in the region next door. The press dots row 4 column 2 and nothing else. The square crosses the border.
A blank grid has no three shades yet, so it does not open on this sentence. It opens on a cell the region's own placements share. This grid's square is a later press. The article still teaches the square first. The same sentence dots row 1 column 2 on a later medium grid, where the opening press has just shaded a T. That press is not drawn. The toast is "Three cells of this 2×2 are shaded, so the last cell stays empty."
Amber wash, a yellow border, and a yellow ring on the new dot at row 4 column 2. The three shades of the square stay ordinary violet. They sit across the border from the dot. The grid is still unfinished. Hint says "Three cells of this 2×2 are shaded, so the last cell stays empty."
The region
List the ways to place this region's tetromino, and ignore the neighbours for this step. A cell in every way is shaded. A cell in none stays empty. One press can write both. A region of four cells has only one placement, so those four are shaded. The button's sentence names one cell even when it writes several.
Every placement covers it Easy
A cell that is in every way to place this region's tetromino is shaded. On a blank grid the right-hand region has five cells: row 2 column 5, row 3 column 4, row 3 column 5, row 4 column 5, and row 5 column 5. Three ways fit inside it. A T uses row 2 column 5, row 3 column 4, row 3 column 5, and row 4 column 5. An I uses row 2 column 5, row 3 column 5, row 4 column 5, and row 5 column 5. An L uses row 3 column 4, row 3 column 5, row 4 column 5, and row 5 column 5. All three cover row 3 column 5 and row 4 column 5. The press shades those two. It does not yet choose among the T, the I, and the L. The cells that only some of the ways use stay blank.
The button's sentence for several cells still talks about one cell. The toast is "Every way to place this region's tetromino covers this cell, so it is shaded." The stored reason names both cells: "Every way to place this region's tetromino covers these cells, so they are shaded."
A region of four cells has only one placement, so the next press shades all four. On this same grid that press shades row 4 column 1, row 5 column 1, row 5 column 2, and row 5 column 3, the whole bottom-left region, one L. The toast is the one-cell shade sentence. The reason is the plural. It is not a finish. That press is not drawn. One shared cell can be the whole press. On a 5×5 medium grid, the top region has two ways left, an I and an L, and both cover row 1 column 4. The press shades row 1 column 4 only. Toast and reason are the same one-cell sentence. That press is not drawn.
Violet shade and a yellow ring on row 3 column 5 and row 4 column 5. There is no amber wash under the shade. Row 2 column 5, row 3 column 4, and row 5 column 5 stay blank. The grid is still unfinished. Hint says "Every way to place this region's tetromino covers this cell, so it is shaded." The reason names both cells.
No placement covers it Easy
A cell stays empty when no way to place this region's tetromino covers it. On this grid the large region still has five ways, and none of them uses row 5 column 4. The press dots row 5 column 4. The square has already dotted row 4 column 2, which was also in none of those ways. The square ran first, because three shades were already there. This press is the cell the square did not take.
The toast is "No placement of this region's tetromino covers this cell, so it stays empty."
The same sentence can dot two cells. On another 5×5 easy grid, nine ways remain in the large region, and none of them uses row 5 column 4 or row 5 column 5. The press dots both. The reason is "No placement of this region's tetromino covers these cells, so they stay empty." The toast is still the one-cell sentence. That press is not drawn. Not every easy grid says this sentence. The 8×8 easy grids do not say it.
Amber on the new dot at row 5 column 4. The earlier shades and the square's dot at row 4 column 2 stay ordinary. The grid is still unfinished. Hint says "No placement of this region's tetromino covers this cell, so it stays empty."
Covered and missed Easy
One press can shade the cells every placement covers and dot the cells none of them cover. On this grid the region is row 1 columns 3, 4, and 5, and row 2 columns 2, 3, and 4. Three ways remain. An L uses row 1 columns 3, 4, and 5, and row 2 column 3. A T uses row 1 columns 3, 4, and 5, and row 2 column 4. An S uses row 1 columns 4 and 5, and row 2 columns 3 and 4. All three cover row 1 column 4 and row 1 column 5. None covers row 2 column 2. The press shades row 1 column 4 and row 1 column 5 and dots row 2 column 2. Row 1 column 3, row 2 column 3, and row 2 column 4 are in some of the ways and not in others, so they stay blank.
The reason is "Every way to place this region's tetromino covers some of these cells and misses the others, so the covered cells are shaded and the rest stay empty." The first cell in the write is a shade, so the toast is "Every way to place this region's tetromino covers this cell, so it is shaded."
On this grid the neighbour sentence was an earlier press. The article still teaches the region's own placements first. The shared cells and the missed cells are one idea. The mixed sentence is the press that writes both. Looking beside the neighbours would have left only the L. This press does not use that.
Violet and a yellow ring on row 1 column 4 and row 1 column 5. Amber on the new dot at row 2 column 2. There is no amber wash under the shades. Row 1 column 3, row 2 column 3, and row 2 column 4 stay blank. The earlier marks stay ordinary. The grid is still unfinished. Hint says "Every way to place this region's tetromino covers this cell, so it is shaded." The reason is the mixed sentence.
Beside a neighbour
Drop the placements that cannot sit beside a neighbouring region. Then the same cover rule. One cell in every remaining way, one cell in none, or both in one press. The one-cell sentences are in the easy group. The easy grids here say the mixed press.
In every placement Easy
Once the neighbouring regions are taken into account, some of the local ways no longer fit. A cell that is in every way that remains is shaded. The press does not yet choose the rest of the piece. On this grid the region is the eight cells around row 4 column 4. Seven ways are still legal if you look at this region alone, and they do not all use row 4 column 4. Beside the neighbours, four ways remain, and all four use row 4 column 4: the S at row 3 columns 4 and 5 and row 4 columns 3 and 4; the T at row 3 column 4, row 4 columns 3, 4, and 5; the S at row 3 column 4, row 4 columns 4 and 5, and row 5 column 5; and the T at row 3 column 5, row 4 columns 4 and 5, and row 5 column 5. The press shades row 4 column 4 only.
The toast is "This cell is in every placement that still fits beside the neighbouring regions." Keeping the shaded cells in one group would have left only the first S. The button stops at the neighbour. This press does not choose that S.
This sentence is in the easy group, and an easy puzzle returns the hint. None of the easy grids here say this one-cell form. They say the mixed press below. The same one-cell shade is row 1 column 2 on a 6×6 medium grid. That grid is not drawn.
Violet and a yellow ring on row 4 column 4 only. There is no amber wash under the shade. The earlier shades and dots stay ordinary. The grid is still unfinished. Hint says "This cell is in every placement that still fits beside the neighbouring regions."
In no placement Easy
A cell stays empty when no placement that still fits beside the neighbours covers it. On this grid the bottom region still has five ways of its own, and two of them use row 5 column 4. Beside the neighbours, three ways remain: the L at row 4 column 1 and row 5 columns 1, 2, and 3; the S at row 4 columns 1 and 2 and row 5 columns 2 and 3; and the T at row 4 column 2 and row 5 columns 1, 2, and 3. None of them uses row 5 column 4. The press dots row 5 column 4.
The toast is "This cell is in no placement that still fits beside the neighbouring regions, so it stays empty."
This is the only press of this one-cell sentence on the grids in this article. It sits with the easy ideas, and an easy puzzle returns it. None of the easy grids here say it.
Amber on the new dot at row 5 column 4. The shade at row 4 column 4 stays ordinary violet. The grid is still unfinished. Hint says "This cell is in no placement that still fits beside the neighbouring regions, so it stays empty."
Some fit, some do not Easy
One neighbour press can shade a cell every remaining placement covers and dot a cell none of them cover. On this grid the region on the right still has many ways of its own. Beside the neighbours, four remain: an I down column 5, a T at row 3 column 4, row 4 columns 4 and 5, and row 5 column 4, another T at row 3 column 5, row 4 columns 4 and 5, and row 5 column 5, and an S at row 3 column 5, row 4 columns 4 and 5, and row 5 column 4. Row 4 column 5 is in all four. Row 4 column 3 is in none. The press dots row 4 column 3 and shades row 4 column 5. The other open cells are in some of the four and not in others, so they stay blank.
The reason is "Some of these cells are in every placement that still fits beside the neighbouring regions, and the others are in none, so the shared cells are shaded and the rest stay empty." The first cell is the dot, so the toast is "This cell is in no placement that still fits beside the neighbouring regions, so it stays empty."
This is the neighbour sentence the easy grids say. On the first easy grid it writes eight cells, and the first of them is also a dot, so the toast is this same one-cell sentence. That press is not drawn. On the other 5×5 easy grid the mixed press starts with a shade, so the toast is "This cell is in every placement that still fits beside the neighbouring regions." Same reason, the other toast. That press is not drawn. Keeping the shaded cells in one group would have left only one T here. The button stops at the neighbour. An easy puzzle still returns this hint.
Amber on the new dot at row 4 column 3. Violet and a yellow ring on row 4 column 5. There is no amber wash under the shade. The earlier marks stay ordinary. The grid is still unfinished. Hint says "This cell is in no placement that still fits beside the neighbouring regions, so it stays empty." The reason is the mixed sentence.
One group
Drop the placements that cannot join the shaded cells into one group, then write the cells those remaining ways share and the cells they all miss. Medium grids need this. Easy walks do not. An easy puzzle still returns the hint. The try of the other mark does not press on these grids.
The shaded cells join Medium
The shaded cells of the whole board have to end as one group. Drop any placement that cannot join them, then write what the remaining ways share and what they all miss. On this grid the region around row 4 column 4 still has the same four ways that fit the neighbours, the four named under "In every placement". Only one of them joins the shaded cells already on the board: the S at row 3 columns 4 and 5 and row 4 columns 3 and 4. Row 4 column 4 is already shaded, so the press does not rewrite it. It shades row 3 column 4, row 3 column 5, and row 4 column 3, and it dots row 4 column 5 and row 5 column 5, which that S does not use.
The reason is "Some of these cells are in every placement that still lets the shaded cells join into one group, and the others are in none, so the shared cells are shaded and the rest stay empty." The first cell is a shade, so the toast is "This cell is in every placement that still lets the shaded cells join into one group."
Every one-group press on these grids writes both marks. There is no press that only shades, and none that only dots. The toast is how the one-cell wording shows up. A 6×6 medium grid says the same reason on two cells: it shades row 3 column 1 and dots row 6 column 2. That grid is not drawn. Medium grids need this sentence. A blank easy walk does not say it. An easy puzzle still returns the hint.
When the earlier sentences stop, the button can try the other mark on one cell. Shading a cell that leaves no way to finish makes that cell a dot: "Shading this cell leaves no way to finish, so it stays empty." Leaving a cell empty when that leaves no way to finish shades it: "Leaving this cell empty leaves no way to finish, so it is shaded." On these grids the button does not say either sentence. There is no separate picture. There is no hard grid.
Violet and a yellow ring on row 3 column 4, row 3 column 5, and row 4 column 3. Amber on row 4 column 5 and row 5 column 5. Row 4 column 4 stays ordinary violet, with no yellow ring. The earlier dots at row 2 columns 3 and 4 stay ordinary. Three cells stay unknown. Hint says "This cell is in every placement that still lets the shaded cells join into one group." The reason is the mixed sentence.
Common mistakes
Check paints a broken rule. Hint will not explain a board that is already broken. The toast is "This board has a mistake, so there is no hint yet." A wrong shade or a wrong dot can also sit there with no coral at all. Then Check says "No mistakes so far. Keep going!" and Hint still offers the next real step, or it finds nothing and says so. The wrong mark stays unless that step writes the cell.
Seven pictures, all on the same blank grid as the opening two shades. No amber on the six broken ones. The quiet one shows the opening two shades, because the board is legal. Coral is the cells the rule names. A region with too many shades paints those shades. Four shades that are not a tetromino paint those four. A region that cannot reach four paints every cell of the region, including a blank. A shaded 2×2 paints its four cells. Two matching shapes paint the two cells that share a side. A split group paints the extra shaded cell, not the dots that wall it off.
Five cells of the large region are shaded: row 1 column 1, row 2 column 1, and row 3 columns 1, 2, and 3. Those five shades are coral. The rest of the region stays ordinary. Nothing is amber. Hint says "This board has a mistake, so there is no hint yet."
Row 1 columns 1 and 2, row 2 column 1, and row 3 column 2 are shaded. The region is not over four, and the block is not a finished 2×2. Those four cells are coral. Row 2 column 2 stays blank and is not coral. Nothing is amber. A 2×2 inside one region, row 1 columns 3 and 4 and row 2 columns 3 and 4, is both a bad shape and a shaded square. That stack is not drawn. Hint says "This board has a mistake, so there is no hint yet."
Row 4 column 1 is dotted. That region has four cells, so it cannot reach four shades. The whole region is coral, including the three blanks at row 5 columns 1, 2, and 3. Nothing is amber. Hint says "This board has a mistake, so there is no hint yet."
Row 4 columns 1 and 2 and row 5 columns 1 and 2 are shaded. Row 4 column 2 is in the large region. The other three are in the four-cell region, which has only three shades, so it is not a bad shape and it is not over. The four cells of the square are coral. The square crosses the border. Nothing is amber. Hint says "This board has a mistake, so there is no hint yet."
One L is row 1 columns 1 and 2, row 2 column 1, and row 3 column 1. The other is row 1 columns 3, 4, and 5, and row 2 column 3. They share the side between row 1 column 2 and row 1 column 3. Those two cells are coral. The rest of each L stays ordinary violet. Nothing is amber. Hint says "This board has a mistake, so there is no hint yet."
Row 1 column 1 and row 2 column 2 are shaded. Row 1 column 2 and row 2 column 1 are dots. The corner cannot reach row 2 column 2. The large region still has cells left, so it is not short. Only row 2 column 2 is coral. Row 1 column 1 is not coral. The two dots are not coral. Two shades on a blank board are not this error, because a blank cell is still a path. Nothing is amber. Hint says "This board has a mistake, so there is no hint yet."
The six pictures above are what Check paints. A wrong mark Check does not see yet is the other picture. With error highlighting off, the extra shades, the bad shape, the short region, the 2×2, the touching pair, and the split paint nothing coral. A swap of one shade on a finished colouring did not leave a picture whose only break is a finished grid that misses the shaded set. That kind is not drawn here, and it can still occur.
The shade at row 3 column 4 is empty in the solution. It sits in the five-cell region. One shade does not put a region over four, and it does not finish a bad shape. No coral. Check says "No mistakes so far. Keep going!" The I in that region no longer fits, and the T and the L still both cover row 3 column 5 and row 4 column 5. Hint shades those two. The wrong shade is not among them, and it stays. Amber is allowed on row 3 column 5 and row 4 column 5, not on row 3 column 4.
A dot at row 1 column 2, row 4 column 2, or row 5 column 4 is also quiet, and those cells are empty in the solution. A dot at row 3 column 2 or row 3 column 3, which are shaded in the solution, keeps the same opening, because the press does not name them. Those dots are not drawn. A dot at row 3 column 5 or at row 4 column 5 leaves the board legal and leaves Hint with nothing to write. Check still says "No mistakes so far. Keep going!" Hint says "No forced cell from here. A shaded cell or a dot may be in the wrong place, so try Check or Undo." That is not the error toast. It is not drawn.
What to play next
Easy grids follow from one region at a time, plus the square, plus the cells the neighbours still allow. A cell every placement covers, a cell no placement covers, and a press that writes both. Then the mixed neighbour press. Start on a 5×5 easy grid. Some of those grids also dot a cell no placement covers. The 8×8 easy grids use the same sentences on a larger board, and they do not say that pure dot. Medium grids add the one group, after the earlier sentences. A medium grid still opens on a cell the region's own placements share. The daily puzzle is a 6×6 medium grid. The one-cell neighbour sentences show up on 5×5 medium and on 6×6 medium. There is no hard grid.
- Easy5×5The region's own placements, the square, and the mixed neighbour press. Some of these grids also dot a cell no placement covers.Play 5×5 →
- Easy8×8Those sentences on a larger grid. These 8×8 easy grids do not say that a cell no placement covers stays empty.Play 8×8 →
- Medium6×6The one group, after the earlier sentences. This is the daily size. Not every 6×6 says the pure dot.Play 6×6 →Today's daily →
- Medium5×5The one-cell neighbour sentences and the one group. The grid still opens on the region's own placements.Play 5×5 →
A printed answer fills the shaded cells and leaves empty cells blank. Dots are not printed. Pieces are not lettered. Four 5×5 or 6×6 grids share a sheet. Two 8×8 grids share a sheet. There is no 7×7, no 9×9, no 10×10, and no 12×12. The printable page is LITS packs.
There is no guide-sized seed to open. The boards above are teaching boards.