or solve online (using our beta test of Penpa-Edit tools)
Theme: Baby in a Corner
Rules: Standard Nurikabe rules.
Answer String: Enter the length in cells of each of the black segments (the unnumbered, connected “ocean”) from left to right for the marked rows, starting at the top. Separate each row’s entry from the next with a comma.
Time Standards (highlight to view): Grandmaster = 1:15, Master = 2:00, Expert = 4:00
Solution: PDF
or solve online (using our beta test of Penpa-Edit tools)
Theme: Easy Logic
Rules: Standard Cross the Streams rules.
Answer String: Enter the length in cells of each of the black segments from top to bottom for the marked columns, going in order from A to B to C to D and separating each entry with a comma.
Time Standards (highlight to view): Grandmaster = 1:45, Master = 2:30, Expert = 5:00
Solution: PDF
or solve online (using our beta test of Penpa-Edit tools; use tab to shift between shading mode and the linex mode where left click+drag draws lines and right click marks X’s)
Theme: “Hard” Practice (this was a WPC puzzle style) — in contrast to this post.
Rules: Place each of the 11 pentominoes into the grid exactly once, with rotations and reflections allowed, to form a valid “Coral”. In a Coral puzzle, all blackened areas are connected, but no group of 2×2 cells is entirely blackened. Also, there are no unshaded areas enclosed by the coral (meaning each unshaded cell must have a path through its edges with other unshaded cells to a border). Numbers outside the grid indicate the lengths of groups of shaded cells in that row/column, but not necessarily in order.
Or see this example from the 22nd WPC instruction booklet.
Answer String: Enter the identities of the pentominoes (one capital letter for each, even if in multiple cells) appearing in the marked rows from left to right (eg “ILN,WVXT”).
Time Standards (highlight to view): Grandmaster = 10:00, Master = 20:00, Expert = 40:00
Solution: PDF
or solve online (using our beta test of Penpa-Edit tools using a composite mode where left click inside cell shades square, left click + drag draws line segment, right click inside cell adds dot, and right click on cell edge adds an x; an additional shading mode is available by hitting the tab button if that is preferred.)
Theme: Clue Symmetry and Logic
Rules: Blacken some cells and then draw a single non-intersecting loop through all remaining white cells. Outside clues indicate the size of all groups of blackened cells in that row or column in order. There must be at least one white cell between each of these groups. When no clues are given, any number of cells may be shaded in that row/column. Or see here.
Answer String: For each marked column, enter the length in cells of the longest vertical segment. Enter 0 if there are no vertical segments. Enter these values as a single string (eg “230124”).
Time Standards (highlight to view): Grandmaster = 4:15, Master = 7:30, Expert = 15:00
Solution: PDF
or solve online (using our beta test of Penpa-Edit tools; use tab to shift between shading mode and the linex mode where left click+drag draws lines and right click marks X’s)
Theme: “Easy” Practice (this was a WPC puzzle style)
Rules: Place each of the 11 pentominoes into the grid exactly once, with rotations and reflections allowed, to form a valid “Coral”. In a Coral puzzle, all blackened areas are connected, but no group of 2×2 cells is entirely blackened. Also, there are no unshaded areas enclosed by the coral (meaning each unshaded cell must have a path through its edges with other unshaded cells to a border). Numbers outside the grid indicate the lengths of groups of shaded cells in that row/column, but not necessarily in order.
Or see this example from the 22nd WPC instruction booklet.
Answer String: Enter the identities of the pentominoes (one capital letter for each, even if in multiple cells) appearing in the marked rows from left to right (eg “ILN,WVXT”).
Time Standards (highlight to view): Grandmaster = 4:15, Master = 6:30, Expert = 13:00
Solution: PDF
Editorial Note: Many solvers can confuse Coral with another puzzle type with similar spelling. An easy way to remember the difference is that Cave has no R’s and also has no 2×2 Region constraint. Coral puzzles, with an R, do have this region constraint. The other general rules (about not enclosing white spaces and having a single shaded group) are shared between Cave and Coral puzzles.
or solve online (using our beta test of Penpa-Edit tools)
Theme: Logical
Answer String: Enter the length in cells of each of the shaded segments from left to right for the marked rows, starting at the top. Separate each row’s entry from the next with a comma.
Time Standards (highlight to view): Grandmaster = 1:15, Master = 2:00, Expert = 4:00
Solution: PDF
(View image directly for larger form.)
or solve online (using our beta test of Penpa-Edit tools; use Tab to alternate between number entry and shading)
Theme: String Lengths
Rules: Variation of Nurikabe and Scrabble/Criss-Cross puzzles.
Place the 12 number strings into the grid, reading from left to right or from top to bottom, so they are all connected criss-cross style and also form a valid Nurikabe ocean. No unlisted string can appear anywhere, not even two-character ones, and the strings do not occupy any 2×2 area. The remaining white cells are part of islands as in a Nurikabe puzzle. Each island is represented by one number in the grid which equals its size in cells.
Or see this example from the 22nd WPC instruction booklet.
Answer String: For each column from left to right, enter the total count of zeroes from the entered strings. Enter the result as a single string (eg “401120…”)
Time Standards (highlight to view): Grandmaster = 7:00, Master = 15:00, Expert = 30:00
Solution: PDF
or solve online (using our beta test of Penpa-Edit tools using a composite mode where left click inside cell shades square, left click + drag draws line segment, right click inside cell adds dot, and right click on cell edge adds an x; an additional shading mode is available by hitting the tab button if that is preferred.)
Theme: Hidden
Rules: Blacken some cells and then draw a single non-intersecting loop through all remaining white cells. Outside clues indicate the size of all groups of blackened cells in that row or column in order. There must be at least one white cell between each of these groups. When no clues are given, any number of cells may be shaded in that row/column. Or see here.
Answer String: For each column from left to right, enter the number of turns the loop makes. Enter your result as a single string (eg “202204…”).
Time Standards (highlight to view): Grandmaster = 1:45, Master = 2:30, Expert = 5:00
Solution: PDF
or solve online (using our beta test of Penpa-Edit tools)
Theme: Triple Play
Rules: Standard Cross the Streams rules.
Answer String: Enter the length in cells of each of the black segments from top to bottom for the marked columns, going in order from A to B to C to D and separating each entry with a comma.
Time Standards (highlight to view): Grandmaster = 4:00, Master = 6:30, Expert = 13:00
Solution: PDF
(View image directly for larger form.)
or solve online (using our beta test of Penpa-Edit tools; use tab to shift between shading mode and the composite Yajilin mode where left click marks cells, right click marks dots in cells or X’s on edges, left click+drag draws lines.)
Theme: Logical
Answer String: Enter the length in cells of each of the shaded segments from left to right for the marked rows, starting at the top. Separate each row’s entry from the next with a comma.
Time Standards (highlight to view): Grandmaster = 8:30, Master = 14:00, Expert = 28:00
Solution: PDF
