Didn't look up for this level a while back ago. Nice hidden answers there. Yeah, it's not that hard to remove the key. Observation needed here. I would say it's a little bit sneaky level.
Gameplay is limited, but very cool design! I never did figure out what the hints were (until I watched @Somnath Mondal 's video), but I found it actually wasn't difficult to solve by trial & error by Spoiler shifting one plank at the time, starting from the farthest one from the key & working inward. Then you're only dealing with 4*5 combinations instead of 4^5 b/c you're looking at each plank independently. Here is a video demonstration of that approach: Spoiler: Video Solution
