Birthday Surprise Puzzle by Prasanna Seshadri

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(Note: This bonus puzzle is at a Saturday+ difficulty, and is being posted today to mark the occasion of Prasanna’s birthday.)

Birthday Surprise by Prasanna Seshadri

(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: 26 on 03/02

Author/Opus: This is the 152nd puzzle from our contributing puzzlemaster Prasanna Seshadri.

Rules: This puzzle combines Yajisan-Kazusan with Tapa with additional rules.

Left grid = Yajisan-Kazusan (No 2×2): Shade some cells black so that all unshaded number and arrow clues indicate the exact count of shaded cells in the given direction (all counts extend through gaps in the grid). Shaded cells cannot share an edge, and all white cells must remain connected as part of a single contiguous group. It is allowed to shade over some of the numbered cells; a shaded over clue may or may not be true. Also, no 2×2 area inside the grid can be fully white.

Right grid = Tapa: Shade some empty cells black to create a single connected wall. Numbers in a cell indicate the length of consecutive shaded blocks in the neighboring cells. If there is more than one number in a cell, then there must be at least one white (unshaded) cell between the black cell groups. Cells with numbers cannot be shaded, and the shaded cells cannot form a 2×2 square anywhere in the grid.

Additional rule 1: Clues in the middle of the grids indicate the sum or the difference of the number of shaded cells in that row between the grids (possibly both).

Additional rule 2: The shading of the green outlined regions is equivalent in the two grids in the shared cells (if the cell labeled “A” in the illustration below is shaded in one grid it must be shaded in both grids). Note that the 3 and 2 share all locations except for the bottom vertical stem of the numbers which is shifted.

Answer String: For each marked row, enter the length in cells of each of the unshaded segments from left to right in the Yajisan-Kazusan followed by the length of each of the shaded segments from left to right in the Tapa. Separate each row’s entry from the next with a comma (but do not use commas in between the Yajisan-Kazusan and Tapa entry parts in a given row). Enter both digits for any two-digit large segment in an entry.

Time Standards (highlight to view): Grandmaster = 30:00, Master = 1:00:00, Expert = 2:00:00

Solution: PDF

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