(Note: This bonus puzzle is being posted today to mark the occasion of Prasanna’s birthday.)

(View image directly for larger form.)

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: 27 years from 03-02-1991 to 03-02-2018

Author/Opus: This is the 160th puzzle from our contributing puzzlemaster Prasanna Seshadri.

Rules: (This puzzle uses standard “Canal View” rules.) Shade some empty cells black to create a single connected group. Cells with numbers cannot be shaded, and the shaded cells cannot form a 2×2 square anywhere in the grid. Each numbered cell indicates the total count of shaded cells connected vertically and horizontally to that numbered cell.

Also, in addition to standard Canal View rules, the clues outside the grid on the top and left indicate the difference in lengths of the largest and smallest shaded groups in that row/column (the smallest group must be >0 cells in size and there must be at least two groups in that row/column). The clues outside the grid on the bottom and right indicate the number of shaded groups in that row/column. All ? clues must stand for prime numbers (2, 3, 5, 7, …).

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 = 10:00, Master = 22:00, Expert = 44:00

Solution: PDF

Note: Follow this link for other Cave variations and this link for other classic Caves. If you are new to this puzzle type, here are our easiest Cave Puzzles to get started on.