This game was originally designed as a substrate for experimenting with procedural puzzle generation (for generating interesting puzzles given a rules set, not for generating new rules sets). I thought I'd post it here, since it ended up being kind of fun to play in it's own right, not just an algorithmic experiment.
I̶ ̶m̶i̶g̶h̶t̶ ̶b̶e̶ ̶m̶i̶s̶s̶i̶n̶g̶ ̶s̶o̶m̶e̶t̶h̶i̶n̶g̶,̶ ̶b̶u̶t̶ ̶I̶ ̶t̶h̶i̶n̶k̶ ̶e̶a̶s̶y̶ ̶4̶ ̶i̶s̶ ̶u̶n̶s̶o̶l̶v̶a̶b̶l̶e̶.̶ ̶T̶h̶e̶ ̶b̶o̶t̶t̶o̶m̶ ̶6̶ ̶c̶a̶n̶n̶o̶t̶ ̶e̶x̶t̶e̶n̶d̶ ̶u̶p̶w̶a̶r̶d̶ ̶o̶r̶ ̶i̶t̶ ̶b̶l̶o̶c̶k̶s̶ ̶t̶h̶e̶ ̶4̶,̶ ̶a̶n̶d̶ ̶i̶f̶ ̶i̶t̶ ̶g̶o̶e̶s̶ ̶h̶o̶r̶i̶z̶o̶n̶t̶a̶l̶,̶ ̶t̶h̶e̶ ̶6̶ ̶o̶n̶ ̶t̶h̶e̶ ̶r̶i̶g̶h̶t̶ ̶i̶s̶ ̶u̶n̶p̶l̶a̶y̶a̶b̶l̶e̶.̶ https://linjat.snellman.net/#game.easy.4 edit: My logic parts a…
I beat it fine; both 6's are horizontal.