Long Live The King!
Lemmings was, and continues to be, the king of the A to B puzzle genre. While modern players can easily spot its flaws, like the lack of a tutorial and the inability to select individual creatures from within a group, the simplicity makes this title truly special. What I mean by this is the rules and physics are clearly defined from the earliest levels, and then they never change. So no matter how mind-bending and difficult some of the puzzles get in the later stages, they always feel fair to the player. This is just about the perfect casual game, and is an awesome way to spend a few minutes, here and there, when time permits.
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