I feel like Factory Balls was a really great example of how simple puzzles games fail in replayability and capacity for extended enjoyment. I quite enjoyed the first 5 or so levels. The initial discovery of how the mechanics worked was really nice, and the feeling of applying those successfully to a few puzzles of increasing difficulty was also great. Then, after a little while, I feel like I had a realization: there was an algorithm I could apply to the game. Start with the innermost color, then cover it, repeat until you did them all. In the first half dozen puzzles I was often failing and retrying, but then I just started seeing the right moves, applying the algorithm and always getting it right. The realization was enjoyable, but the game stopped being a puzzle game: the puzzles stopped being puzzling. The game might have gotten more advanced later on if new mechanics were introduced, but it felt like I had solved this sort of boolean operation puzzle, and there was nothing left for me, no discovery of solutions. This can be a really hard problem to solve for puzzle games that rely on one key mechanic in a relatively small state space: it’s easy for the mechanic to run out of juice after a few levels, and then the fun is gone.
