Could you please let me know which puzzle made you feel like you didn't understand the rules? I tried to introduce every mechanic/interaction with a very small puzzle to make sure that it's hard to get it wrong, but I might have missed something.
About the line showing the solution - yes, this is coming probably sometime in late January, along with some other updates due to the feedback that I've received. I didn't include it in the first public build because keeping the line readable in puzzles where you can visit one square 5+ times while not obscuring the puzzle itself is not trivial.