S...Space??
Magrunner goes off the rails a bit in its third act. Not the story -- the story was never on any rails to begin with, floundering helplessly on the side of the track. No, what starts to fall apart in the third act is the gameplay mechanics. There are enemies that you need to "fight" by magnetically hurling things at them, and there are chases that are just totally out of place. These wacky tangents converge in a final boss fight that was obviously rushed out the door, where even the victory condition is completely unintuitive.
That aside, there were only a couple of places where I really felt like the game's puzzles were unfair, i.e. mechanics or objectives were cruelly non-obvious. In general, Magrunner's puzzles are really well-designed, and the amount of content is pretty admirable as well. Although the first act's levels tend to go by pretty quickly, in its second act, Magrunner presents some real head-scratchers. Forget the fact that this isn't really how magnets work; this is a good Portal-like puzzler.
What makes it fall short of Portal, in addition to the aforementioned third-act decline, is Magrunner's narrative weakness. The intro is pretty cutscene-heavy, as is the finale, with a pretty disappointing ending to boot. And there's only one character - the mentor - in the whole cast who's worth a damn; the protagonist has no personality whatsoever, other friendly characters come and go without a second thought, and even the villain is a flat, throwaway stooge. Although Magrunner succeeds in setting up a Lovecraftian atmosphere, its story elements are thoroughly underwhelming.
Despite those shortcomings though, Magrunner is definitely worth its running length. Its core puzzle mechanic is unique enough to support some really fresh puzzle design, and its atmospheric twist is unlike anything you're likely to have played before.
Better than: Quantum Conundrum, Q.U.B.E.
Not as good as: Portal, Portal 2
Story not as good as: Event Horizon
Progress: Finished on Normal