The core game itself is really good and surprisingly deep, but the presentation needs some serious work on usability and performance.
Visually, it's difficult to distinguish between shades of bright white. It strains the eyes after just a few minutes, and if my vision was even slightly worse it would have rendered the game unplayable to begin with.
The game is really, really slow -- gratuitous glowing on everything is a CPU killer, and animations to load, finish, and restart levels are pretty long to begin with. I wound up opening a forum tab specifically to kill time while it was chugging through animation, and probably spent half my time in those instead of your game.
The lag is a double problem, because it also means you drop enough frames that mouse drags don't register their start where I put them, and with no way to undo or cancel moves I have to sit through the long restart animation even more often than I would in the natural course of solving puzzles.