I find it a fun game to waste a little bit of time. Since it gets harder as the levels progress, it's a nice challenge. Very fun and addicting game.
On the level select screen, it would be nice to have some sort of color coding or other visual indication as to whether or not all of the rhombs have been collected for each level. As it is, you have to mouse over each level in order to see, which isn't the easiest way to quickly see what's left to be done.
On level 20, the bottom green line is a dirty liar. Aside from that, great little game.