There are over 40 rooms for exploration. It's okay to draw your map and take notes. I have only solved one puzzle and decided to give up after watching the first few minutes of a walk through video.
First, any spot on a scene is clickable. Therefore, there's no way to find out whether you have missed something or not. It can take a lot of time to use a tool in a scene (e.g., digging in the graveyard and checking loose tiles). Second, some items including crystals just blend in so well with the background and are hard to spot (e.g., a screwdriver). Also, I had no idea where I could use the wooden pegs and a cog. Third, it is easy to miss a knob in a shower room that opens a secret pathway to the underground. I didn't know about it until I read the walk through comments. Last but not the least, I found the file information in the cabinet overwhelming other than being able to pick out two entrance codes. Journal entries, in contrast, are interesting for reading.
Overall, the game isn't well designed although Selfdefiant might have put in a lot of effort in setting the crystals, ordering the scenes, and adding some hard puzzles for us.