If you are not a nerd, I wish you a merry Christmas and the best wishes for 2025, but please do not read any further, it might make you unhappy.

Dear fellow nerds: imagine a bathroom with a size of 100 x 103 tiles, with 500 robots randomly distributed across the room

Every robot has a different speed and direction. E.g. one robot goes 2 tiles to the right every second and another one goes 3 tiles to the north east every second.

When a robot hits a wall, it will not crash but magically re-appear at the other side of the room.

Now the question is: after how many seconds will the robots be positioned in such a way that, when viewed from above, they together form the image of a Christmas tree?

It took me quite some time to figure it out, but eventually I got the solution! In my case a picture of a Christmas tree appeared after 6577 seconds.

I then made a drawing of that tree. In that drawing every robot is represented by the number “1”, every empty tile is a dot.

So, if you are bored during the Christmas holiday, go and solve the puzzle yourself at the Advent Of Code website: