The Rat Returns. And Loves The Number 13...!!?

[@neil2796]

I'm waiting for the puzzle that lets Finkz take the direct route. That'll throw Simon for a loop.

[@HirrumiHassan]

It would be fun, if Finkz goes only 2 or 3 squares 😂😂

[@Gnalistair]

April fools' day surely

[@stevieinselby]

I'm pretty sure Marty has said that he had wanted to do that for an April Fools puzzle, but was struggling to find a way that the rest of the grid could be disambobbinifed without having to put in a load of given digits or extra clues that had nothing to do with Finkz's path as that wouldn't be true to the genre (and it would probably be quite obvious from looking at the puzzle that there was something afoot). But I live in hope that someone as creative and devious as Marty will find a way!

[@neil2796]

@@stevieinselby The difficulty of making it work was definitely on my mind when I was writing the comment.

[@kenrickman6697]

The only way I can imagine it working is some kind of parallel timeline type thing where there are two paths, one simple, one convoluted, and something at the end of the solve disambiguates the two options.

[@HarleyMaebry]

The fact that the cupcake was a 3 in the corner deserves more fanfare.

[@jeremypalmer5695]

1:03:09 "We don't know if that's green" * screams of anguish internally*

[@martysears]

Thanks for another fun hour Simon… This was as fun as ever to watch. I was very aware that this ruleset was longer than usual, due to having quite a few different clue types in there. I usually try to limit it to 2 clue types max + the test constraint, but I thought a slightly crazy one would be ok, as long as it used mainly previously seen clues, and I don’t make a habit out of it :) I had known since the start that I wanted episode 13 to be themed around the number 13, but I didn’t know exactly how until recently. Jobo’s excellent puzzle Row Sum Lines provided the inspiration - there he used lines that were like region sum lines except for rows rather than boxes. This got me thinking about what if you do rows, columns and boxes all at once? I realised firstly that that could be a very fun path finding puzzle, then secondly that it could be brilliant for a Rat Run puzzle, and finally that it would be perfect for episode 13. It is such a forcing constraint - any cell found to contain path immediately has implications across the whole grid. This means that more than most Rat Run puzzles, there are probably a myriad (or even a plethora) of different journeys you could take through this solve, hopefully converging on certain key deductions. But once you start getting lots of digits filled in, useful information to progress starts coming in from left, right and centre. My original reason that Finkz must visit the top left-hand part of the grid was actually nothing to do with the sensors… merely that the cake was occupying a single cell in row 1, and so more needed visiting in row 1 to make 13. Simon is right, this did take a lot of fiddling to get a path that totalled 13 in all rows, columns and boxes… it goes to show how flexible and forgiving the maze format is that I was able to set this in just a few days. Being able to put in walls wherever I like allows me to do all kinds of things 😀 More nonsense next week! 💜

[@davidrattner9]

Just more exceptionalism from you Marty!! Such a joy to see you set and bring love to Simon and all of us!!

[@brianj959]

Another absolute winner, Marty. Your inventiveness is a bottomless well! 👏👏

[@dimabolsunov5678]

Awesome puzzle!

[@AditaBattleForge]

Marty, this was delightful! I really wonder how you go about setting these puzzles, do you have a special software for that?

[@martysears]

@ thanks 😀 the puzzles are made in SudokuMaker, which is really good for aesthetic flexibility, and it has a solver built in which does sudoku on clues you put in and finds if there are any solutions.

[@TFMurphy]

The secret of Triskaidekaphilia is something that Finkz only tells her favourite people -- and if you're helping her get cupcakes, you're definitely one of those people -- and it has to do with the fact that the values of the cells she visits in any single row, column or box of this maze always sum to....

[@michaelpdawson]

Since Simon kept calling the nullifiers "negators," he should just combine the two words and call it a nulligator. 🐊

[@debrabowen4276]

There once was a fellow called Marty Who liked giving Finkz a nice party There was cake to be had Which made Simon go mad And poor Finkz had to run round quite hearty!

[@kenrickman6697]

“There could be all sorts of weird sudokuness.” Such as the 7 in c8 disambiguating r3c7/8. Simon, I am truly in awe of your account to comprehend and apply such a complex rule set! Sometimes I feel like missing the obvious aspects of sudoku is just a consequence of you working on a higher plane. Never change, please!

[@austinish]

It's also easily proven for a good 10 minutes or so by asking where the nullifier in box 3 is. So basic sudoku and funky rules both point to fixing that pair. Still got a few minutes left, but if I had to guess which one he spots first XD

[@Kradlum]

Finkz took a diagonal turn at every opportunity.

[@Dazreil]

That’s one of the unspoken rules of rat race puzzles, if you can do a diagonal move, you probably will

[@mermaid_hina2713]

Anyone else waiting for Simon to notice he had 5 path cells in box 4?

[@MadsOcto7]

And he was just examining the x's 😭

[@reiswhite7767]

THANK YOU

[@emilywilliams3237]

He was not idle, while you noticed the box 4 situation he was noticing many other things.

[@DRayX701]

Yes, very much so. He was so carefully checking all the rows and columns, and just ignoring the box where he clearly already had five lol

[@aleksapupovac]

It took me a long time to realize there are five path cells in row 1

[@matthiasney4871]

I love - and understand - the Rat Races more than any other Sudoku on this channel. I think it is the unconventional, less sudokuesque approach we always need for the break-in that helps. I am not that experienced in classical Sudoku solves and often lack the knowledge or do not see a certain deduction (especially when Simon does his colored pairs). The rat races however always has a unique, never seen before logic to start with. Thank you so much Marty for these brilliant, funny and sweet puzzles!

[@emilywilliams3237]

I came to this a few days after it was posted and I'm so glad I did. What a lovely puzzle, and what a great video, Simon. I would have had trouble getting started, but you homed in on just the right aspects to focus on. I might have to try this series at some point, get over being intimidated! Thank you for this video.

[@adammolski]

1:13:08 WE NEED someone to draw Simon and Finkz sharing a cupcake together

[@Anne_Mahoney]

What is Finkz's view on frosting? Simon is going to want a cupcake 2 inches high with a 2 1/2 inch layer of frosting on top, all chocolate. Can rats even eat chocolate? Or are her cupcakes carrot cake with cream cheese frosting? Can they compromise on gingerbread, perhaps? 😺🐀🧁

[@chocolateboy300]

I finished in 111 minutes. This felt like the hardest Rat Run for me so far. My brain was very slow in scanning the rows and columns for 13 clues. It is such a cool ruleset to do, though. I really liked the way the pathway occurred. It felt like I got most of the path pretty quickly. It was proving the final parts that felt hard. Marty did not disappoint as it was still real fun to work through. I think my favorite part was seeing that no matter what I put on the motion sensor in r7c3, a nullifier appears in column 2 in box 7. The story is quite intriguing and I can't wait to see where it goes from here. Great Puzzle!

[@debrabowen4276]

I adore the Finkz videos! Watching these, it occurs to me that Simon and Marty Sears are like opposite sides of the same coin.

[@martysears]

I take that as a massive compliment!

[@JustLookingHere]

03:02:35. Took me way too long.... But slowly i build the path and slowly added digits. I really wanted to finish this one and i was pretty confident i had the correct path. Just adding the digits had me staring at my grid (which was overloaded with color). But it was fun and i love path puzzles. Also really like how there is some kind of story added to it. I am amazed people think of this and make it a reality.

[@rockyshi6714]

Finish in 94:51. The is my favorite one in this series because Marty fooled me twice. I spent quite long time to check if my previous deduction was wrong. 1. grape can have a 5 if it is paired with a zero. 2. motion sensor can be zero. ( It is awesome that Simon found that at the first glance) But I love puzzle just because of these moments that I found the only way to solve a problem that I has thought can not be solved. It's nonsense but solvable! I would repeat the fact that everybody watching this channel know: Marty is a genius!

[@QwDragon]

Coloring of non-path cells is more efficient than crosses on their boundaries

[@КонстантинИванов-я9к3ю]

In this puzzle coloring is more appropriate for nullifiers indication

[@aliengeo]

I find it charming that Simon, after once misgendering Finkz in ignorance, now takes care to point out her gender. Rat feminist ally.

[@FrancisFjordCupola]

Love Finkz. Found her eating only half the cupcake rather ominous. I'd love to see a RatRace where Finkz is forced to take the direct route ... but ... with it being proved rather towards the end as a twist that cracks open the puzzle.

[@davidrattner9]

Marty ...Marty. Starting to get loss for words for you and this magnificent series!! 😁 Fabulous solving path, logic and deductions from Simon!!

[@emilywilliams3237]

I agree wholeheartedly!

[@thomasr2472]

I played every single Finkz puzzle, and they're all great, but this one is the best! Took me 65 minutes to solve, and I enjoyed every minute.

[@PauxloE]

Nice puzzle, though it took me quite a while. At the end I had a deadly pattern with only digits off the path and on nullifiers ... I was about to give up, but then remembered a rule I didn't have to use until now. Total time 165:28, solve counter 821. As a German, I'm happy to finally see a German Whispers "line" with a 5 on it.

[@PauxloE]

I also used yellow and green, but inverted. (In my palette, the yellow is more screaming, and the green is more pale, so I guess it works better that way.)

[@HunterJE]

One outcome of the "no more than 5" initial observation available out the gate is Finkz cannot go below the horizontal wall between rows 8 and 9; while at first glance that only uses 5, it would have to turn up at both ends to avoid taking a fifth cell in its row, which gets her stuck on a path that requires at least 6 cells in box 8...

[@PauxloE]

Also, it requires to use a forbidden door.

[@kosumi68]

Lovely puzzle. Never loses the flow, and still surprises at every turn.

[@davidblake6889]

The impossible Simon does instantly. The obvious takes a bit longer... Great solve nevertheless! Thanks.

[@markp7262]

44:29 finish. I can't even begin to imagine how this was set up. Absolutely amazing!

[@dollarsing]

Simply marvelous. Thank you!

[@Afterthoughtbtw]

There's going to be an April Fool's version of one of these where the start and end point are next to each other, isn't there? Albeit, I can't decide which would be funnier - if the path just went directly, or if it nevertheless had to go all around the grid first.

[@stevieinselby]

@@Afterthoughtbtw With something like a German whispers constraint along the path, you could certainly make a puzzle where Finkz starts off next to the cupcake but can't go directly to it.

[@PauxloE]

If Finkz doesn't go through the rest of the grid, getting enough constraints to actually get digits in might become difficult.

[@A_CC_K]

Yes a another Rat Run, loving the series, Marty Sears has an insanely brilliant mind. So is Simon when he solves them.

[@jadeEpeace]

Thanks Simon and Marty for a great puzzle and solve. I loved solving and watching this one ❤

[@HunterJE]

Finkz rewarded at the finish line with a cupcake AND a song!

[@HeiniGurke]

..and ate only half of it. I am a little concerned. She needs to eat more. More mazes, more cupcakes please. And no Schrödinger's rat experiments, don't go that route!

[@alexanderbaldwin9916]

Simon, you solve puzzles that I never could, sometimes you draw conclusions from evidence I didn't even notice, and you've entertained me while doing so for months now. But it will always drive me mad when I noticed something in the first 15m that you still don't see after 50m. There is always one, or maybe two, things I notice very quickly and then you either never notice or don't notice for so long that I start to lose it a bit.

[@AppelmoesArtandPhotography]

I’m pretty sure I can speak for a lot of people when I say that these rat puzzles are one of my favorites. 🐭🐀

[@helencooper286]

Definitely!

[@piarittersporn]

What a big challenge. I think I am now infested by “Ratomania” because even after ages I can't stop looking for a solution. And finally I could solve it.

[@Coyotek4]

31:18 ... after a long work week, it pleased me to no end to see a continuation of Finkz's odyssey! LOVE these puzzles!

[@lennartmuijres664]

28:37, ever since I found out how to use the line in sudoku pad I enjoy these type of puzzles a lot more :)

[@HunterJE]

44:21 One way to eliminate 5 on the motion sensor there is it would need a natural 8 below it to hit the sum for box 7, but that natural 8 would also be a fifth path cell in row 8 which would give a minimum four-sum of 8+1+2+3=14

[@mordirit8727]

1:08:21 I fear Finkz is getting too smart for me, this one was a very tough cookie to crack and I dread that soon I won't be able to run one of these without checking Simon's help first... Nothing but pride for this genius little rat!

[@JPgreekgaming]

Finkz is back! This will be great.

[@AaronPriceColby]

That first grape nullifier completely threw me, needed a lot of help on this one!

[@skid68]

Like that Simon rarely takes the easy way, like having a 9 on an X but finding out some other way it is 1 :) (I totally understand he misses it, so much to keep track of)

[@themiddleones11]

Now I need a wrogn puzzle with X-nif, the rat that just does all the wrogn things😊

[@ryboits75]

One of these days, Marty is going to make the path to the cupcake the simplest one and it will bamboozle us all

[@gappy3234]

It felt like forever for me to get started and work out the top left path, but I'm gratified to see it took Simon a while too (though he was still faster for sure). I actually also realised I made a false conclusion that the bottom sensor had to be a nullifier, when it could have been a 1, so that was lucky! This is also a rare maze puzzle in that the route doesn't go bonkers in the final 2 boxes - though for a long time I was working on the assumption that the cupcake would be a nullifier, just because that's the sort of thing that happens.

[@stevieinselby]

I worked out for myself that each house could have at most 5 visited cells, I twigged that if any of the motion sensors were nullifiers then Finkz wouldn't have to pass within range, and that Finkz must somehow visit the area of the maze in the top-left ... but after re-starting the puzzle 2 or 3 times, I kept getting stuck at the same point ... the motion sensor in box 2 saw 5 visited cells, but 5 can't go on a grape cell 🍇, and if I bent the line to make 6 cells around the sensor then that also put 6 visited cells in the column and so it was broken. After staring in bemuslement for a few more minutes, I gave up and started to watch the video ... and while Simon was still exploring the same ideas that I had already gone through something clicked in my head and *Marty Sears I shouted your name and swore very loudly* 🤣 ... I won't try to pretend it was _easy_ from that point on, and I _still_ ended up breaking it and restarting again, but Finkz did eventually get her cupcake 🍰🐀 and then I went and got some cake too because I'd earned it

[@martysears]

Hehe I’m used to having people swear at me 😅 cake well earnt, I say

[@iabervon]

I've learned, when there are modifier cells in a puzzle, to reread the rules and note every time it says "value" because that means that rule isn't necessarily going to follow the secrets I know this time, and even if it does, it may mean something extra.

[@matthiasney4871]

I love the Rat Race Puzzles because the opening is always more abour general logic and less about knowing the tricks of Sudoku. I maybe solve 50% of the other puzzles without having to check the video at one point ( mostly it is some coloring trick or sudoku deduction I didn't see), but with the Rat Races I stand at 13/13 now. Thank you so much, Marty, for these clever, funny and slightly different Puzzles. You are my sunshine in an otherwise ugly week.

[@roccov3614]

It occurred to me that if a sensor was a nullifier, I wasn't sure if it meant that Finkz doesn't trigger the sensor, or the sensor is zero regardless of if Finkz moved in range. So, I came looking for an answer. If I understand you correctly, you are saying you assumed Finkz had to stay away from a nullified sensor but that didn't work. So, I can move in range of a nullified sensor? Is that right?

[@martysears]

@@roccov3614 no, you were right the first time. A nullifier on a sensor would mean that that sensor has a value of zero, indicating that Finkz doesn't move into that cell or any neighbouring cell...

[@roccov3614]

51:50 Simon worked out the path in box 6 differently than me. I did it a lot earlier and I think an easier way. If the path didn't divert to the left in box 6 then column 6 would be made up of only 2 cells in box 8. Those 2 cells would have to add up to 13 for the column but there are other cells on the path in box 8. So that would be impossible.

[@moby4177]

Was that actually Brie in the corner?

[@farbiarnarrr4767]

This puzzle is awesome!

[@y_prime]

solved in 39:01 - definitely the hardest rat run so far, but very rewarding as always. I also used the sensors to get the path to go through the top left part of the grid

[@mscha]

Excellent puzzle, like all Rat Runs! For me, this was the most difficult one so far. Took me about 3 hours over several sessions, giving up more than once. That motion sensor in the bottom left was especially evil - in a good way.

[@_ernst]

44:47 - if in Box 7 the top-right motion sensor turns out to be the nullifier (zero - 0) then the sequence 5 - 0 - 8 (top to right) is perfectly valid and the Nullifiers would be box 4, cell 8 and box 7, cell 3... and the world would still be ok. Lucky Simon, that Marty Sears didn't chose to mislead the solver in that way ;)

[@aleksapupovac]

Off topic, but I'm pretty sure the grape in box 7 isn't even needed.

[@MarkBennet10001]

Brilliant puzzle, lovely solve: Simon (almost) always sees things that I have missed.

[@chipsounder4633]

Trying to think of a poem to write. Sat head scratching most of the night. As you can see my mind has gone blank. Marty Sears' puzzles are back.

[@SwordQuake2]

38:05 FFS BOX 4 1:03:10 it has been known for ages

[@ericpraline1302]

Very enjoyable as ever, thanks, and I managed to continue my honourable tradition of stuffing up rat run puzzles due to careless mistakes. Outshone by a rat.

[@stangerrits6712]

What a way to find that 7 in box 6 at 55:40. A couple of minutes before Simon did all the calculations in row 6 to deduce what needed to be on the black dot, only to jump to another part of the grid instead of completing the 13 on the path in row 6 :) His mind works in funny ways...

[@remybeauchamp]

This is REALLY weird. Last week, a puzzle by Marty referred to October 30th 1974 in the intro, which is the day my best friend was born. And now, this puzzle refers to November 6th 1974, which is the day I was born. This is blowing my mind!

[@-ARatnakumar]

53:00 I was thinking how would Simon miss the easy deduction like that in box 3 when he got the 9, but he waa waiting for all of them to count.Classic

[@barmetler]

By the end of the puzzle, I placed digits so that a row or column or box would be 13, and seeing how automatically the other directions became 13 too was amazing. This must have been so difficult to set, to make sure things can add up to 13 in all these directions without clashing with other rules.

[@emdiar6588]

Brilliant!!!!

[@petermawhorter9016]

Got this one in 06:17:05, and had a huge amount of fun with it.

[@domanski123442]

I see Finkz i am happy 😊

[@coconuts2513]

Im at the 18:00 minute mark, and my prodiction is that at least 1 motion sensor has a nullifier on it, and at least one green grape will be a "zero" nullified cell paired up with a 5.

[@Aliessil]

Finished in 53:30. I do hope Finkz isn't getting sick!!

[@janerobson2297]

Shouting look at the path cells in box 4 is driving me mad!

[@ryanstadther]

Marty please make the next one a direct route! Simon will lose his mind 😂

[@logiclrd]

At 49:00, couldn't the cells on the line have been 1-2-6-4, with the 6 being on the green dot, and then the motion sensor's 5 be nullified? R2C5 being labelled a possible green wasn't intended to exclude R2C4 from being a possible green, as I understand it...

[@francoisduez601]

Once again, a-maze-ing rat race puzzle ! ❤

[@przemekmajewski1]

me waiting for ages for Simon to count that there already is 5 path cells in box 4...

[@mudscuffer]

1:12:36 for me. I've really liked most of these, and this one was still good, but maybe a few too many rules. I completely forgot about the nullifier uniqueness until the end when I reread the rules.

[@artursruseckis4242]

The reason why Finkz cannot go to cupcake quickly is because he must make top row path sum to 13 which is impossible with just single cupcake cell. It is all about 13 in this puzzle. And once you determine that Finkz cannot move upwards through box3, you know you MUST go to boxes 1 and 2 via box4 to accomplish that and then there is just one possible pathway back via boxes 1-4-7-8-9 when the path again becomes ambiguous. So the basic outline of Finkz path is quite obvious from the beginning, no sensor logic is required there.

[@aartbluestoke3352]

todays maths fact: "15 is more than 13" Is there a list of these nuggets of wisdom somwhere?

[@AaronPriceColby]

OMG, I was having so much trouble with this until I watched to 34mins and saw that it's not just the boxes but the rows/cols that matter for 13s

[@Timlagor]

Simon looking very fuzzy today

[@joopysalem16]

18:57 R7C1 is not detected by motion sensors

[@grantfraser5430]

Such an unusual and inventive rule set. I haven't figured out the time travel element yet. Why is this puzzle set 50 years ago?

[@martysears]

It’s not time travel, it’s just set in the past, like Pride and Prejudice, Gladiator, or Saving Private Ryan 😀

[@Gonzalo_Garcia_]

43:15 for me. Toughest puzzle in the series so far, I really struggled with those nullifiers.

[@isakoolsson]

That white 5 and half white 4 in the end looked very sad 😢

[@tBagley43]

1:00:29 fun puzzle, had to reread the rules several times

[@georgewhyte7096]

Fantastic well done

[@msgeryjo]

Half the cupcake? Are we expecting a rat run with Finkz and baby Ratz?

[@srwapo]

101:39, sorry, Finkz, I needed help with this one. I thought r9c2 could be a negated digit, but forgot that later when I figured out the line had to go down through row 9, and I totally didn't think that r2c5 could be negated. There's a lot of neat patterns going on that I wish I used better.

[@Ardalambdion]

2197 seconds would have been the perfect solving time.

[@awilliams1701]

There are a few puzzles where I feel like the rules need to be better. I think it was number 7 says it has a custom rule, but the description doesn't mention it. I was able to solve it. There is another one with region sums that must have all digits 1-n. The rules don't mention that they have to be unique lengths. I got very far, but in the end I got stuck. I made the assumption that each line is unique and was correct. I don't know if I missed something or if that's missing from the rules, but I think unique lengths should be in the rules.

[@awilliams1701]

anyway.....puzzles 1-15..... complete.

[@martysears]

I assume you're not talking about Rat Run puzzles here? There hasn't been one where region sums must have all digits 1-n... and there are only 13 episodes published so far

[@awilliams1701]

@@martysears the fog DLC.

[@awilliams1701]

@@martysears BTW the sudoku pad doesn't have quick rules (Which is what I was talking about) it only has the rule dialog box. The CTC app has quick rules (which I LOVE!) and the full dialog.

[@TimWalton0]

The 5 on the green dot kills me. I know there is a "value nullifier" cell, but I thought this was only for adding up the totals of the segments. Pah, failed again! I ruled out a 5 in that position which then impacted the rest of the puzzle and it went pear shaped. (I find the nullifier rules, and "wrong" rules hugely frustrating)

[@PsychoSoldierPrometheus]

Treis is 3 in Greek. Deka is 10 in Greek. (Decathlon, etc). Philia is friendship in Greek, or, to like something. Treiskaidekaphilia means to like the number 13 @CrackingTheCryptic

[@krisdelacourt3977]

at 1:00:10, simon refusing to actually do sudoku while claiming to do sudoku.. :) with two 9s looking at box 1

[@energythief]

Some sudoku in box 1 would have shaved 15 minutes off this one. :)

[@soulseek2]

drink every time he says negator instead of nullifier

[@PinkSupervisor]

I focused so hard on boxes and rows that I forgot to check columns halfway through the puzzle. Needless to say I took way too long. Sorry Finkz.

[@PeterZaitcev]

All hail the rat god!

[@marino1805]

I really like here how SMALL SPOILER FOR END: how it ended with the unique nullifiers, which i forgot about.

[@tantricsarcasm9133]

"You rotten puzzle" - that's a new one :)

[@nicholasiverson9784]

13k views in 13 hours, well done

[@iceberg54321]

The rules should state that the cell Finkz starts on, and the cupcake cell are on the path.

[@mathewmallon7208]

If you could make a surguestion to Marty having Finkz run a (lightly) "steam" filled maze

[@martysears]

Haha what would the steam do?

[@mathewmallon7208]

@martysears trying to emulate a "fog of war" puzzle

[@martysears]

@@mathewmallon7208 episode 10 had fog 😜

[@mathewmallon7208]

@@martysears forgot that

[@markthompson2874]

Personally I'm going to count my time of 42 minutes since I was able to get Finkes to the cupcake in that time. Took me about 16 more minutes beyond that in order to finish the Sudoku.

[@artursruseckis4242]

Simon was too quick to understand the 5*0 grape logic. For me it was a disaster, I got to the point where the sensor must be 5 and I went "ups, mistake somewhere". And got stuck trying to understand what I did wrong for minutes 10-15. Then there was that enlightenment moment - "Oooooh, that's beautiful!" Was hoping to see something similar from Simon, but nah, not today :(

[@hairyspice]

I know I am always wrong with these things, and I am sure there is a very simple and likely obvious explaination, but how did Simon rule out R2C4 being the nullifier at around the 25:30 mark? He states that it can be a 5 if R2C6 is a nullifier and continues with that logic, but couldn't it also be a 5 if R2C4 itself was a nullifier at that point?

[@hairyspice]

I worked this out almost immediately after I posted it and can't believe I didn't spot it. It can't be a 0 when it's a motion sensor with the path right next to it. It's clearly one of those days...