1. I had to fly the LS all the way to the right of the map first, while building reactors as quickly as I could without falling into a deficit.
2. Next, I used shields to hold off the drones by keeping everything I built very close to the surface.
3. I constructed three phantom coils just before the phantoms hit, and at a similar time I managed to get a blaster online to take out the drones just as my last shield fell (I used a phantom coil as a shield!).
4. After digging for some space for more reactors, I had to put up a repulsor to keep the creeper from spilling onto the land. The blaster was set to only target drones.
5. Slowly but surely, building another repulsor every now and then, I pushed the creeper back with the help of a mortar. My energy supply became really stretched so it took ages to make progress.
Here is the point at which victory became pretty certain:
