[Hard] Simon Says


Here’s an interesting challenge. It’s a little game of Simon Says against Magnus. You have to program Magnus to behave as follows:

  • You manually release two balls of any color by pressing the corresponding levers
  • Magnus then immediately follows by repeating this two-ball sequence
  • After this, you can start again, choosing a new two-ball sequence
  • Your first ball and Magnus’ second ball need to be intercepted and not automatically release a new ball
  • You can play endlessly by emptying interceptors and refilling ball supplies as needed

Example: You release a blue ball and then a red ball. Magnus then automatically responds by also releasing a blue ball and a red ball. Note, as some balls are intercepted, the actual output at the bottom is not RBRB. It is about the balls that are released from the top.

Let me know what you think. Is the challenge clear? Are you able to solve it?


No replies yet. Is it too hard, or has nobody yet seriously tried it?

In case anyone wonders, this is solvable on a normal board. My solution, however, requires slightly more parts than are available in the basic box. It is a beautiful solution though. I’d like to share it, but will wait until someone else has shared their solution, or made a serious attempt but has given up. Let me know how you get on!


I have a solution with only parts from the set.


This was a very nice puzzle, and it stumped me for a long time. I finally solved it after you mentioned it was solvable on a normal board.


Your solution appears to work for the first 2 balls, but the spec wanted something that you can continue to play until the balls run out, with you inputting 2 balls then Magnus outputting 2 matching balls then you inputting 2 and Magnus again repeating your play, and so on without needing to reset anything manually…


Oh. (I actually hate 20char)


Your solution is definitely in the right direction! It has an important ingredient in common with my solution, the two-track four-state “router”. However, it still has some unnecessary complexity, and as rmsgrey already indicated, only works once. You still need to set it up such that it returns to its original state after every “game”.


I give up. :frowning_face: :white_flag:


Here’s the solution that I had in mind:

It requires one purple gear and a crossover more than are available in the box, but other than that, I think it’s pretty sweet.

The trick next to the 4-state 2-track router is to add a 1-bit storage at the beginning. It stores the color of the current ball and returns the color of the previous one. For the first ball, only the storage is relevant, for the third ball only the retrieval, for the second both, and for the fourth ball neither.


Good puzzle, kept me busy for a long time! Here is my solution:

Unfortunately, some pieces need resetting between turns. The top four gear bits are weighted (2 with balls inside, two with cogs) to behave like blue bits.


Hi Rob,

I am happy to hear that you liked the puzzle.

Unfortunately, your video does not load (yet?). Can you fix this? From the photo it’s not immediately clear to me what the starting state should be, so I could not easily try your solution. You mention that some pieces need resetting between turns. Which ones? It does suggest that it’s not fully solving the problem though.

I like how you creatively replaced some parts. Nevertheless, maybe you should get yourself some extra spare parts :slight_smile:


Youtube is normally very fast but seems to not have processed my video properly hours later. Uploading again hasn’t helped (yet).

The starting position is as in the picture - the central line of gear bits are all centred, so the first ball to hit will always bounce back the way it came from.

I definitely need to buy some more gear bits for complex machines like this, especially as I seem to have misplaced one of mine and am down to 7 until I find it!


I have a better solution! No need to reset bits between goes and no extra parts needed. :sunglasses:

Youtube uploads are still not working for me so I have shared my video here: https://photos.app.goo.gl/eqeFv3zTQHjFELoK9



The crossover+cog+interceptor is the same ball capture-and-release device I first shared in July. The crossover raises the cogs so rubber washers are needed behind the other two cogs to raise them a bit too. Not sure if how much they help, but some extra rubber washers are also used to add a tiny bit of weight to cogs to partially balance the weight of the two interceptors when up.

The two unconnected gear bits have balls inserted in the triangle. This makes them act just like blue bits, but faster. This is necessary as the first ball needs to reach the bottom significantly faster than the second ball for everything to work correctly.


Wow, that’s an original solution to the problem, featuring some creative usage of parts and the parallel ball drop is ingenuous as well. I don’t think this solution can be modelled yet in the existing Turing Tumble simulators!