A guide for S200_151 Golphomin, which was classified as impossible until WookieDaMasta recently completed it.

My strategy was to hold off the creep with a mortar and terp.

The build order:

• Collectors in the juicy spots. Build 1 at a time initially.
  
• 2 reactors
  
• Another 2 reactors
  
• Mortar
  
• Terp
  
• Reactor
  
• Terp up wall
  
• 6th reactor
  
• 2nd mortar
  
• 7th reactor
  
• 3rd mortar
  
• 5 more reactors
  
• 4th mortar

Building up the wall was done in stages, to height 9 first and then 10. The priority is:

1. Bottom and its corners
   
2. Top right corner and top edge
   
3. Right edge
   
4. Top left can be left at 8 until the main walls are completed.

After the 4th mortar, the position is stable for a while and I could carefully expand to the right.
Adding on the extra column of units gives just enough reach for the command node to reach both of the tech totems.
Getting 2 Energy Efficiency upgrades makes things a lot easier.

• Units don't need to be on a 3x3 square. The corners can be left off.
  However if the unit leaves the rounded square it might not be able to return. To fix this, remove terp numbers, terp up the corners, or remove adjacent units.
  
• As mentioned by others, when bouncing the command node around, you can save energy by not undoing the direct link between command node, terp and mortar or wherever the energy is going.
  
• A lot of saving and loading is needed.

Reference:

• Knucklecracker notable maps[knucklecracker.com]
  
• WookieDaMasta strategy