That's a very good point and we want to add that feature. Is the fact that it redraws the map based on the current state of the lines visually useful? I would like to redraw the official tfl underground map

Yes, I rather like it. In fact, with the appropriate lines removed, 90% of the time I wouldn't even need it to navigate for me - and it's definitely good for more fuzzy journey planning.

I can't see such a thing anywhere on their website, but in stations TfL often have the inverse; a map showing the closures with the rest greyed out. I've always felt that's the wrong way around.

Thanks. We felt for London commuters just the live image of the map would be enough to enable them to visualise their route. And for tourists/infrequent users the added route planning would show them how and why they should take a particular journey. You can also manually open and close stations/lines and get instant feedback on how that effects the planned journey (although this is mainly hidden in the UI)

Just a heads up, the schematic Tube map is updated every 3 or 4 months. A member of my team tried mapping the points manually with appropriate curves in Canvas, ultimately it was a bit of a nightmare without the original Illustrator SVG file. It might be a painful task for you.