FTA: “As a motivating example: player 1 (hereafter dubbed "Red") can win by playing in the center column on the first move and then following the weak solution's suggestions, but would not be guaranteed to win if the first disc is played elsewhere. The weak solution contains no information about what would happen in the other columns- As far as Red cares, it would be redundant to learn those branches, since they are not good.”

I don’t think that “since they are not good” is necessary for a weak solution. Even if every first move were winning, it still would be redundant to learn how to win for every possible opening move.

A weak solution gives you a guaranteed way to move from START to a win, whatever counterplay, not all ways to go from START to a win, whatever counterplay.

This guy’s videos are awesome. He also has one on Klotski and the double pendulum. Beautiful graph animations.

> which is fundamentally different from existing strong and weak solutions

It doesn't seem fundamentally different from Victor Allis' solution, but 2swap managed to generalize and streamline the rules available for static solutions, while also picking the winning moves that reduce the overall tree size.

> A weak solution can be visualized in a way that a strong solution (14tb uncompressed, 350gb compressed) cannot.

That is using an overly strict interpretation of strong solution. My database of all roughly 68000 8-ply positions allows for computing the best move from any position within seconds and takes only 12KB compressed (using one trit per 8-ply position, 5 trits per byte, using remaining 256-3^5=13 values for run length encoding).

[1] https://tromp.github.io/c4/c4.html

I'm surprised no one linked to his video on the topic. I can't overstate how high quality it is. The graphs are simply beautiful, and it made me think he had a whole production team behind him. That he was able to do cutting-edge work like this (it's new, which qualifies) while creating a work of art is incredible.

"I Solved Connect 4" https://www.youtube.com/watch?v=KaljD3Q3ct0