Spiral Lands is 100% free.
Spiral Lands is a collection of puzzle games set in a colorful fantasy world.
The puzzles are based on Pipes, Links, Islands in the Stream (Nurikabe), and Light Up (Akari).
All the puzzles are algorithmically generated, and can be played at your own pace.
Story mode is a nice introduction to logic puzzles for beginners. Eternal offers infinite puzzles of increasing difficulty. Challenge mode lets you change puzzle settings and instantly solve them if you wish.