### Sunday Surprise: 100th Puzzle Spectacular by Prasanna Seshadri

(View image directly for larger form.)

(After solving the puzzle (or before, if you desire) look at this additional image for another challenge.)

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. Note that the default puzzle info is too long — even for an url shortener — so copy and paste all the text in this file into the “Load” option in the upper-right of the penpa-edit interface to access. You can then also open a new tab and copy in all this file for the final additional challenge.)

**Theme:** Clue Symmetry and Logic

**Author/Opus:** This is the 100th puzzle from our contributing puzzlemaster Prasanna Seshadri.

**Rules:** This puzzle combines styles that involve shading cells. All rules are standard for the given puzzle types (Tapa, Light and Shadow, Nurikabe, Kurotto, and Cave) which appear in the indicated spots of the grid (see below).

*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.*

Light and Shadow: Divide the grid into shaded and unshaded regions, each containing exactly one number and with an area equal to that number. Numbers in white cells are part of white regions; numbers in shaded cells are part of shaded regions. Same colored regions cannot share an edge.

Nurikabe: Shade some empty cells black so that the grid is divided into white areas, each containing exactly one number and with the same area in cells as that number. Two white areas may only touch diagonally. All black cells must be connected with each other, but no 2×2 group of cells can be entirely shaded black.

Kurotto: Shade some cells so that each circled number represents the total count of shaded cells in connected groups sharing an edge with that number. Cells with circles cannot be shaded.

*Cave: (The inside of the cave with the numbered cells is shaded here!) Shade some cells to form a single connected group — the cave — with no enclosed, unshaded cells. In other words, all unshaded cells must be connected by other unshaded cells to an edge of the grid. All numbered cells must be a part of the cave, with each number indicating the total count of cells connected vertically and horizontally to the numbered cell including the cell itself.*

Additionally, there are two diamonds made out of cells in each grid. Each cell in the smaller diamond corresponds to two cells in the same position in the larger diamond (see example below). The corresponding cells must differ in their shading (i.e., if a cell in the smaller diamond is shaded, both corresponding cells in the larger diamond are unshaded; if a cell in the smaller diamond is unshaded, both corresponding cells in the larger diamond are shaded).

**Answer String:** Enter the answer to the additional challenge in ALL CAPITAL LETTERS (no spaces)

**Time Standards (highlight to view):** Grandmaster = 25:00, Master = 32:30, Expert = 1:05:00

**Solution:** PDF

Excellent puzzle. I really enjoyed this one.

This was great. I really enjoy these interdependent marathons. Aside from this, Prasanna’s 9 Shady Masterminds, and Palmer’s Octathlon, what other puzzles are there in this genre?

Many years ago I made a 100th puzzle mix on my old blog.

Palmer made a much much harder combination for the 2013 MIT Mystery Hunt called Portals. I soloed it in about 6-8 hours (with mistakes, in the middle of the night). I remember it having a narrow path.

You can also try the Black and White Matrix from this LMI test/WPC practise test: http://logicmastersindia.com/lmitests/?test=M201309P2

Congratulations, Prasanna. I’m currently working my way through this amazing puzzle, but I’ve gotten stuck. Can someone please help me figure out the flaw in my logic below? Thanks!

Va gur ahevxnor, gur 9 vfynaq zhfg fgergpu ng yrnfg 6 pryyf qbja, juvpu zrnaf gung va pbyhza 10, gur pryyf va ebjf 5 naq 6 ner hafunqrq. Nf gurl ner pryyf cneg bs gur fznyy qvnzbaq, gurl sbepr 4 pbeerfcbaqvat pryyf gb or funqrq va gur xhebggb (E4P4, E5P5, E6P5 naq E7P4). Guebhtu xhebggb ybtvp, fvapr gur 1 va pbyhza 3 vf sbeprq qbja, gur 7 zhfg tb nyy hc, naq gur 6 zhfg tb nyy qbja. Jura ybbxvat ng gur 14 va gur 9gu ebj, V svtherq bhg gung vg unq gb tb zbfgyl (vs abg nyy) gb gur evtug, juvpu sbeprq gur 2 gb tb gb gur yrsg naq hc, wbvavat gur funqrq pryy va E7P4). Gung zrnaf gung gur 14 arrqf gb tb pbzcyrgryl gb gur evtug, ohg gung vf cebivat gb or vzcbffvoyr.

Lbhe ybtvp frrzf svar fb sne. Xrrc guvaxvat nobhg gur 14.

Gunax lbh! V unqa’g pbafvqrerq gung gur 14f pbhyq ernpu rnpu bgure…

Amazing Puzzle.Was a delight!!

2hr and 6 min to decipher this and arrive at the answer.

Meh, 30 minutes with the cave colors flipped 🙁

Fun puzzle though!

That was really fun, thanks for the great puzzle Prasanna! Like Jonah, I really like these marathon puzzles where there are multiple subpuzzles that affect each other. The “additional challenge” was also very fun to decipher.

Great puzzle!

Thank you.

Awesome work Prasanna, thank you!

Very nice puzzle! Thank you Prasanna!

Finally cleaning up some old puzzles, going to see if I can slowly work on catching back up to current. This seems to be where I left off, but I ended up jumping the gun a bit. In looking at the final page, I started to see where it was going, and moved to the last task with less than 50% of the front puzzles done. Still fun, though.