### Hidden Shape Sudoku by John Bulten

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or solve online (using our beta test of Penpa-Edit tools; use tab to alternate between Sudoku number entry mode and two drawing modes, Special and Surface, to mark the shape inventory.)

Theme: Snakes on a Sudoku

Author/Opus: This is the 16th puzzle from our contributing puzzlemaster John Bulten.

Rules: Standard Sudoku rules. Also, there are some shapes that must be put into the grid. The shapes can be rotated, but cannot be reflected; they can touch but cannot overlap. (Not all cells of the shapes contain numbers, but all numbers on the shapes must be entered into the corresponding cells after placement.)

Answer String: Enter the 2nd row from left to right, followed by a comma, followed by the 8th row from left to right.

Time Standards (highlight to view): Grandmaster = 10:00, Master = 30:00, Expert = 60:00

Solution: PDF

Note: Follow this link for other less common variations of Sudoku and this link for classic Sudoku. If you are new to this puzzle type, here are our easiest Sudoku to get started on.

• Aaron Chan says:

How do you actually do this puzzle without guessing? I ended up doing a lot of trial and error + intuition on it.

• Tom Collyer says:

I’m not sure I want to leave spoilers so early, but there is certainly a logical way into the puzzle using those 5 pieces. And when test-solving this everything suddenly fell in to place!

I’m a grandmaster!

• skynet says:

If there ever was something called hard….

Lost track of time.Glad to finish it….

• ghirsch says:

The break-in took a while to find and work out, but it was an impressive puzzle. I’m curious about what the intended path was though, since even after narrowing things down a lot I still had a good amount of trial and error in my solution.

• LorenR says:

For me: It took a while to see the big picture logic. However, once you see it, there is ZERO trial and error required to find the solution. Like Tom, I don’t want to post a spoiler yet. ROT13 (minor hint): Pbafvqre gur svirf; gung vf gur xrl gb haybpxvat gur ragver chmmyr.

• ghirsch says:

No worries, I agree that it’s best to avoid spoilers for now since it’s pretty tempting for people who haven’t solved it yet to look at them, especially in a puzzle like this.

• Aaron Chan says:

V qvq pbafvqre gur svirf, ohg gung fgvyy yrnir dhvgr n srj jnlf gb cynpr gur cvrprf. V vaghvgrq jung znxrf nrfgurgvp frafr sebz gurer, ohg gung gb zr vf fgvyy gevny naq reebe.

• hagriddler says:

I can give you 5 nudges in the right direction, if it’s too much please remove this post.
I advise to try one hint at a time, and only come back for the next if you are still stuck :
1. Vtaber gur tvira ahzoref sbe abj, rkprcg gur svirf.
2. Ner gurer ebjf/pbyhzaf jurer gubfr tvira svirf pnaabg or cynprq ?
3. Jurer pna gur svir or va gur pragre guerr ol guerr fdhner ?
4. Pna lbh svg gur bgure sbhe svirf pbafvqrevat gur funcrf gurl ner va ?
5. Ol abj lbh pna gnxr n ybbx ng gur bgure tvira ahzoref…

• Aaron Chan says:

V tbg gur svefg gjb uvagf gur svefg gvzr V fbyirq vg, ohg V fgvyy pnaabg frr ubj lbh pna qrqhpr gung gur svir zhfg or ng gur pragre jvgubhg rkunhfgviryl gelvat bhg nyy cbffvovyvgvrf.

• ghirsch says:

@hagriddler Zl fbyir cngu onfvpnyyl sbyybjrq gur fgrcf lbh yvfgrq, ohg 3 naq 4 ner gur cnegf V gubhtug bs nf gevny naq reebe (V nz thrffvat gung vf gur fnzr cneg Nneba qvq). V’z abg fher gubhtu vs V nz zvffvat n ybtvpny fgrc gurer gubhtu be vs lbh whfg unir n qvssrerag ivrj bs jung pbhagf nf gevny naq reebe.

• hagriddler says:

Wowzers ! That was impressive !
At first I did a lot of trial and error but then I threw all of those notes away (including the shapes I cut out in an attempt to move and rotate them around the grid).
Finally I found a more or less elegant way to solve it logically.

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