Sprouts 2026 Afterthoughts

Sprouts 2026 was yesterday!  It was a success!  I have lots of thoughts.  Now you can read them! 

• Stats:
• We had 10 contributed talks in addition to our keynote.  (1 total less than last year, which is the record so far.)
• We had our largest number of recorded attendees.  Right now that number is at 60, though I think I saw some people that were not officially registered.  (Not a significant problem.)
• We had the most ever number of players in our human tournament: 18.  The tournament lasted well over an hour!  (Oops!)
• We tied our record of the most ever number of computer players with six.  Two of those came in during the conference and I was able to integrate them anyways! 
  
  
• The 2026 Battle Sheep human world champion is JiaJian Zeng!  NGMI won the computer tournament.  Sadly the humans lost the John Henry match this year.
   
• I need to move my "crash course" style talks online.  Many of the attendees know all that information already.
  
  
• One of the speakers created their computer player during the morning of the talk and submitted it!  It is not a trivial player!
   
• My dropbox syncing wasn't working and I didn't realize it until almost too late.  One computer player was submitted in the middle of last week and I didn't see it until some of my students told me they had also submitted players on Friday afternoon.  Oops!  I had already updated the instructions to tell people to email me when they make a submission; hopefully that will prevent this issue next year!
  
  
• Craig and I need to plan the board size better.  With 20 people playing in the tournament, I think we should ballpark that a round of human matches will last twice as long as a play through between the two of us.
  
  
• In addition to the board size causing the human tournament to last a long time, I need to update my tournament page to allow manual entry of a box of line-separated names to make that faster.
   
• We need to give better instructions to the speakers, remind them to plan to talk for only ten minutes, and be prepared to cut them off.  
   
• We probably need to switch to registration via a web form to collect the email addresses of attendees/speakers all in one place.
   
• I'm sorry we didn't really have our chatty "End with Friends" session, but I'm glad we got to hold the entire tournament and get all the talks in!
   
• I need a better method of running the computer tournament.  The players took too long for us to run the tournament on their own in the allotted 15-minute window.  What we did is that I ran it in a separate browser window, but I didn't time it correct for everyone to watch the final round.  I wish I could bring another laptop, fire it up on there, and then log in to zoom with that and have the video feed be the screen capture of that window.  Then attendees could click over to that screen to check in on how the players are doing.  I don't know how to do that without having that other laptop be doing a "screen share" which would be cumbersome to everyone else.
  
  
• I did get the request to get the computer player stuff set up earlier so people can do student projects with it starting in September (or even August).  We'll see what we can do!
  
  
• During the event I can be quite busy behind the scenes.  (It was exhausting, but also sort of fun!)  Yesterday during talks I was often also doing one or more of these:
• Processing registrations that were still coming in.
• Prepping the Battle Sheep page to include the computer players so it could be used for the John Henry match.
• Taking notes on the talk.
• Integrating the late-entry computer players into the computer player tournament page.  (Sorry I made you choose between your two players, Anne!)
• Trying to sort out time-zone confusion. 
• Making executive decisions with Craig. 

 

It was go great!  I hope next year goes just as well!

Sprouts 2026 Summaries

We held Sprouts 2026 yesterday!  We are so lucky to get such awesome talks!  Here are my summaries of each of them:

 

Arjun Agrawal: "Collecting Coins on Trees"  

Arjun introduced an impartial scoring game on a list of cards.  Each turn a player selects a card at one of the two ends of the list and adds that value to their score.  Arjun gave a O(n) strategy for the first player to win on even-length lists.  The algorithm replaces trios of cards with an equivalent single card when possible until the list is bitonic.  He showed that some concepts can apply to trees, and is looking for a working algorithm.

 

Shounak Ranade and Siddhesh Umarjee: "Winning Goat Strategies for m x n and Infinite Bagh-Chal Boards"

Shounak talked about Bagh-Chal (Tigers and Goats), a popular asymmetric game.  They analyzed the cases for multiple different planar graph geometries.  In Bagh-Chal, goats try to surround tigers, who can jump over goats to capture them.  On an n x m grid, they showed that 2n goats are enough to trap a tiger and win.  They also adapted the angel and devil game solution to show a finite (4156) number of goats that can trap a tiger on an infinite grid.   

 

Aditya Khambete: "The rulesets Expansion and Void Expansion" 

Aditya talked about the games he showed at Waseda in Tokyo last month.  Expansion is played on a grid with some blue and red tokens on spaces.  A turn consists of choosing a connected component of your color and expanding it by placing a token on all empty adjacent nodes.  Aditya was able to find many values including integers and dyadic rationals.

 

Sahana Jahagirdar: "Omni-Fission"

Sahana also talked about a game she discussed at Waseda: Maxi-Omni-Fission.  In this game, players play on a board of black and white stones.  On their turn, a player selects one of their stones with at least two empty neighbors and removes it, filling all of the neighboring spaces with their stones.  She analyzed a bunch of situations to find winnability and values.  

 

Keynote: Neil McKay: "Digraph Placement: Insight and Exploration from a simple ruleset"

Neil talked about Digraph Placement, a game played on a directed graph where vertices are colored red and blue.  A turn consists of a player choosing a vertex of their color, then removing that vertex and all vertices the chosen vertex directly points to.  (If a is chosen and there is an arc a->b, then b is also removed.)  Then he talked about universality of normal short games, of which Digraph Placement is one.  He showed the constructions for all 22 games born by day 2 using at most four vertices each.  Neil showed how to build ordinal sums from two graphs and then showed other ways to build general constructions needed to prove universality.  He continued by talking about the succinctness of universal games. He compared the sizes of his constructions to Tree and showed that they're significantly smaller.  Neil talked about conflict placement games: games where once a certain move becomes illegal, there is a single particular prior move that caused that illegality.  He finished up by talking about how they found all 1474 values born by day 3.

 

Adir Ali Yerima: "The winning strategies for the Sparse Ruler game" 

Adir talked about the idea of the sparse ruler, which has the minimum number of marks necessary still measure all integer distances from zero to n.  He turned this into an impartial game: a turn consists of adding a mark to a ruler of length n with the game ending when all distances are measurable.  (Meaning, there is a pair of marks that distance apart.)  Adir wrote a bunch of python to analzye (and illustrate) game trees.  He found the nimber values of initial positions of sizes up to 20 and found what appears to be a back and forth repeating pattern.

 

Stephen Zhou: "Finite Cardinalities of Misère Quotients"

Stephen talked about Misère quotients with the destination of showing that there cannot be a quotient of size three.  Misère quotients are sets so that other games can be shown as equivalent under addition with all elements of that quotient.  No games are equivalent to another under { * }, so that is not a useful quotient.  Stephen showed his constructions for quotients of all sizes except three.  These used games with the awesome name Blue Mutant Flowers!

 

Emily Decker and Chase Pittman: "Stickerbook: A New Impartial Game" 

Emily and Chase talked about Stickerbook, where players mark vertices on a grid, but lose if their move creates any 2x2 grid of marked (by either player) spaces.  (They analyzed this as a normal play game, so the square can never be completed.)  They found nimbers for many m x n board, then showed that 4 x n (>=2) is always in P.  Emily and Chase went on to show that for odd n, n x n is always an N-position!

 

Anne Pham: "Grid Slime Trail is PSPACE-complete" 

Anne described her work on Slime Trail, a game where players move a token around on a grid trying to move to their specified goal vertex.  Spaces cannot be visited more than once!  She played against the audience (and won).  Anne then gave a great description of reductions and PSPACE.  She described her reduction from QBF to Slime Trail, specifically grids, showing off the variable and choice gadgets in detail.

 

Abraham Hsu: "Solving 6 x 6 Othello with Blob Databases" 

Abraham talked about the GamesCrafters group at UC Berkeley, where they strongly solve games using heavy computational resources.  He talked about how their prior method of using shards doesn't work with Othello because pieces can flip.  The solution is to use what they term as blobs to store the position data.  This improved their data requirements way down from the previous 3^36.  Abraham has used this technique to solve the 4x4 game in less than a second per query, down from multiple seconds, and is working on the 6x6 solution.

 

Soumitro S. Dwip: "Corner: An Integer Partition Game" 

Soumitro talked about Corner, a game on Young Diagrams where a move consists of choosing a subset of boxes at the far right of rows where there is no box below and remove all the chosen boxes.  Soumitro and his team are currently working on a proof of a way to determine outcome classes very quickly.  They are also looking into determining the Grundy values and misère Grundy values! 

 

The talks this year were amazing.  We agreed that they would not have been out of place at all in one of the international (non-undergrad) conferences!  I am so lucky to be a part of this every year!  I can't wait for Sprouts 2027!