Lines Of Action
This game was designed by Claude Soucie and I found it in Sid Sackson's book A Gamut of Games. Board Game Geek has a page devoted to it with links to videos explaining the rules.
Rules
Victory is having all pieces connected into a single cluster. At the start, each player has two separate clusters. A piece is connected via a friendly neighbour on at least one of its eight neighbouring squares. A player reduced to one piece automatically wins.
There are alternating moves, black starts.
In their turn, players can move one piece in a straight line, including diagonally, the number of spaces equal to the number of pieces in that line.
A piece can move over friendly pieces, but cannot end its move on a friendly piece.
A piece cannot move over enemy pieces, but can end its move on an enemy piece, eliminating it.
AI
A reason I picked this game was it's in Stanford University's General Game Playing library with a kif version but I couldn't get it to work, so rewrote it in Prolog from scratch.
For anyone interested in discussing my homebrew framework or the game, I started threads on Reddit gamedev, the SWI-Prolog discourse group, and Board Game Geek.