http://www.coragames.com/games.html It's free and fun. Michael Contento is the author.
The rules of Space Dots are pretty simple: connect the squares in sequential order, and make sure your path covers all of the squares.
As you can see, there are 216 'Advanced' levels. I've done them all and all of the 216 Bonus levels. I also did the 216 6x6 collection. The vast majority of them I completed in under 20 seconds.
I really like these puzzles and always have. I think that Numeric Paranoia offers harder puzzles. But my perspective could be based on the fact that I've done hundreds, if not thousands of these. I did struggle on some of the Space Dots, but not many.
Numeric Paranoia costs money, while Space Dots is free.
The graphics of Space Dots are much nicer.