The enjoyment someone gets out of Painajainen depends on how much you enjoy certain modes of playing. Like in its inspiration Seiklus, you’re a small, whitish stickman who runs around in a 2d platformer landscape, solves puzzles and has no fear of death, since there aren’t any enemies or other dangers around. You aren’t told what to do, but that’s not much of a problem, since Painajainen is mostly self-explanatory.
There’s a rare bug where after going from one panel into another you can’t move anymore, but with a quick hit on E you are teleported back to the first panel (and since the game is rather small that isn’t a problem) and you can backtrack from where the bug stopped you. The only section of the game that was a bit annoying was the star turning-on puzzle, but even that is doable with some tries.