Very trying but all 30 levels are possible.
Awesome game, beat all 30 levels. Only 4 stood out and those only took some creative reworking to finnish. I agree the one with the black blocks remove some of the challenge as they provide a definite guide line for what can go where.
If your running into trouble try to have your lines either avoid completely or inclose both end points of any lines inbetween its own end points.
Most puzzles can be sumed up in that they are like onions. There are multipule layers, each going around the next. This is the same with the lines. Each line goes around another line which goes around another line which goes around another line and so on.
If an end point is 1 away from the edge, it's a sure bet that something is going to be going around that end point.
Either way, no level is impossible, if your aproach fails try a completely different way. Some levels make it obvious what needs to go where while others take a long time to grasp.
Spoiler:
On the level you have to wrap Orange around the whole cube (somewhere in the twenties, 27?) It's like a snake when you have to get past blue, green, and purple. From the top left go down then up around the lower purple then above the green and down again to reach the path to the other orange end point. Once you do this all other paths should automaticly be obvious.
