Gave up after it started getting into the longer levels. Not because I couldn't do it, but just because I could make a single mistake near the end of the game and I would have to redo the whole level.
There seems to be this common issue with puzzle games, especially a bit unpolished ones, wherein they don't bridge the gap between a very small margin of error and a very long level.
An undo button would be great with that. Yet as it stands, this puzzle falls into the same trap as others.
If a level is long, it should not be easy to make a mistake that ruins it.
If you can make a simple mistake that forces you to re-do an entire level, the level should not be so long where it causes the player to groan in frustration when they're forced to restart.
An undo button is a great in-between.