Uhh...This is strange, I was on the first day (no bear traps), and a fat woman zombie just started doing the heebie jeebies dance that they do when they get clamped by a bear trap.
Holy crap, can't believe I did it...But I just got the impossible badge!
Tips for level E keyboard; You don't have to be that careful throughout most of the level...You can save all of that for the part with the spikey spiral paths near the end. At the end, go down, not up...Its a much shorter and easier path. When you make it to the circles in the middle, don't take the shortcuts...Take the first short path, then after that, all of the long ones, until the spikey spirals.
Holy crap, I made a big level, so its not small enough to post on here...But, if you have a Mountain Bike and you go fast at the beginning, you ride your bike backwards!
Here are two level walkthroughs.
Level 6-- Shoot a portal above top square, and one below you. Walk to the right edge. Shoot two portals, one below one arrow and one below other. Jump into one the arrow is pointing to.
15-- Shoot blue portal in top left wall. Shoot orange portal near glass. Jump into orange portal to loop-jump over to the ledge on the right. Before landing, however, shoot blue portal at the ledge's ground. You should do a pendulum-style loop jump. Wait, and time your run into the fryer-pad when its black, and jump to exit.
Need any other level walkthroughs? Send me a shout on my profile.