Great submission! Id say you may need some more visual clues such as mouse hover over pop-ups as well as more things to get people going at the start to figure out how to play. My other suggestion would be that the Z key isn't too intuitive as a keyboard game player. Either sticking that in the UI somewhere or changing it to a more normal E or F would be the way to go.
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At first, I want to add an outline when the pointer hovers over the object. But I just think it will be too easy for the player to solve the mystery. Yeah, I've got to find another way to tell the player which object they should be staring at.
And you should use the arrow key to move the pointer, I forgot to disable WASD movement xD