I love nonograms! Sometimes I wish there was a more defined grid here though. Also on level 4, one of the columns says that there are no black tiles on it, only for there to actually be one.
Also the hints aren't really aligned with the columns very well, so I'd sometimes have to count the hints across just to make sure I wasn't about to use the wrong hint.
All issues that could easily be fixed with a little bit more dev time.