I liked it

The puzzles were challenging enough that solving them brought a feeling of accomplishment.

It's a good game even without all the little details that would have given it a smooth, professional feeling.

Those little details that could use some improvement are as follows:
1. A little animation, sound effect, or something following the solution of a level. I'd like to be able to just sit there and admire the completed grid for a little while.
2. Background music. Just so players could get into the atmosphere of the game.
3. Sound effects.
4. Tidier graphics. It would be so much nicer, as a game that requires a bit of time spent to solve, if the graphics were easy on the eyes.

That's about all I can think of. Thanks for a good game!