Thank you for the kind words!
Yes, removing lines later on was intentional as they served as a tutorial in the beginning. Hope I could make that clearer, but it is how it is in 2 days :)
And about several solutions: it was impossible to change levels after we set them in stone (drew on paper), so we could not deal with a couple of unintended solutions in levels 4 and 5, which is probably not the worst thing after all!