Took me forever but nice image.

Hard one, but logical. Amazing ;)

I could really use a hint on this one!

That was a tough one, but really good, thought I would have to use temporaries as I got stuck, but then didn't, very logical :)

Wow, tough one and great image! Thank you, Mystifier!

Row 1: C 1, 3, 5, 8-12, 23, 25
Row 13: 1-2, 7, 13-15, 21-25
Row 24: 1-2, 6, 8, 11-13, 16-19, 24
Row 25: 1-3, 6, 10-11, 17-18, 24-25.

Fab image. thanks.

Fully logical. Hints are nice, but the puzzle can be solved without hints too. Thank you!

Nice one, thank you!

This is a perfect puzzle - hard, but fully logical with a nice image as a reward. Thank you!

How about one simple hint? just fill the upper right corner.

Thank You.