I tried this great game called 3D Logic by Alex Matveev(warning: his personal site is slow from the U.S., but the game site is fast) at the game site http://www.thatvideogamesite.com. It's a flash puzzle game and lots of fun.
Some of the 3D Logic levels can be VERY hard, so I decided to post this page with my solutions to level 16-30. The levels before 16 are not very difficult so I didn't think to take screenshots of them before I finished them, sorry if you are having a hard time with one, no offense.
Here are the solutions or answers or whatever you want to call them with one block near the end of a segment either missing or wrong (because when you finish it, it disappears immediately). If you know the game it will be quickly obvious where the missing or incorrect block is because the segment endpoints are black: