This map reverses gravity at 1:50 on the timer, causing all the mice to die unless a roof has been built. The gravity reverts to normal at 1:30.
Stay near the shaman at all times. The shaman will either try to build a temporary shelter from the gravity or won't.
If you suspect that the shaman will not be building, you can employ a "wall clinging" technique to avoid death. A simple way to live through this level (even if the shaman doesn't build) is to cling, which is where you cling to either side of the stage. In order to do it, wait until the timer is a few seconds from 1:50, then hug the side by running into it. This will use the same exploit that wall jumping uses and will allow you to remain relatively static to the wall. When the shaman dies and brings the timer down to 0:20, wall jump back up and claim your cheese. It isn't perfect however, as it will not keep you alive for the full 20 seconds of the reversed gravity. It is important that you are sure that the shaman will die and prematurely return the gravity back to normal if you want the technique to work.
If you see the shaman start building, just hope you have enough time to make it under the shelter before the gravity kicks in. Also, if you leave the shelter at 1:32, you will rise and then fall back down when gravity returns to normal, which can put you closer to the cheese and allow you to get first.
Build a shelter before 1:50, lest you let your team of mice die before your eyes. Most commonly, shamans only have time for 1 or 2 simple red anchored planks, which does hold if balanced correctly. Alternatively, spawn a large transparent box, then red anchor a long, solid plank to the top. This guarantees that the planks will stay immobile. If you can build a decent shelter before then, you should take that opportunity. However, be sure to have a way back to the hole after the gravity turns back to normal at 1:30.
Also, a good shaman tactic here is suicide. By doing this in first 10 seconds, the shaman can reduce the timer to 00:20, so the gravity reversal would not take place at all. This is very helpful if you are on Hard Mode.
If you would like, you can build the roof closer to the middle so that the lead pack can make it under the roof after taking the cheese.