Note also, im certain there is room to improve, im not exactly a spectacular player.
At the start, I place three reactors near where I plan to put the LS, and start trying to claim the surface tech chip, and plot out my dig routes to save time later.
About 7 seconds in, i have the first tech in hand, pause, get the reduced cost, packet speed boost, and energy storage boost., start a shield all the way left. You will need to both replace it, and increase the height of the wall before long
The first drone or two will go straight for the LS, this is ok, you can take 5 hits if they are spread out, and taking these hits leaves your shields alone for a few seconds longer. From here its pure energy management. You need more reactors, I think this can be best done by getting to one of those gems as quickly as possible. I just dig and place reactors when my total stored energy reached 4 units from the delays in digging. Given your weak energy state initially, stop digging if you have to build shields.
32 seconds in I start going for the first gem. The moment I have that gem in hand, several things occur. I drop a blaster above my LS, one shield to defend it from stray drones, and reactors everywhere I don't plan to dig, plus I start moving on the second gem. note that the moment your last packet goes out for the first gem its time for a third shield on top of the two already there as the creeper is beginning to get deep. You'll also need one more behind the bottom one soon as well.
I have the second gem in hand at 1 minute in, a blaster, the first firing rate upgrade, and some room for more reactors now that i have a surge in energy. I place another blaster behind the stray shield that defended my first production. The odds of them being attacked there is low, but it may happen, and they can't move until complete, so...
1:09, i have my second blaster online, have spent all my bonus crystal, almost have the next tech, and im getting close to the fourth tech. I save the next tech and use them both to grab the second firing rate upgrade. I found it necessary to have that firing rate in order for my line to hold. Note that there is one tile in my bottom row i don't dig up until after i have grabbed the tech, I do NOT slow my collection of the tech for anything. I found it necessary. As before, build reactors when you have 4 or more energy to spare, this lets you grow without slowing your progress for the tech.
1:19 im about to expose the tech, and have enough excess energy to work on a blaster at the same time. Given my spare energy production at this point(low excess, it doesn't grow fast, I open the bottom row just as my last packet for the tech leaves. i'll be needing that for energy VERY soon.
1:24(note, time may not be possible to match with previous, I screwed up and restarted for this point) I've now got the last two weapon techs, and spend them on the next level of firing rate. its costly, but gives me enough sustained output to get through the surge.
1:41....showtime!(erg, forgot the image) I have 4 blasters, and am 5 walls deep on the bottom where most of the drones will try to pass. I've also curbed my energy needs for the moment to ensure my blasters do not come up short at this critical juncture
1:50 looks like a winner, its not quite over, but most of the surge is dead, things are almost down to a sustainable level. note that you can reconstruct my defence from here, since nothing moved. I've lost three shields on the bottom, and one in front of my blasters on levels 2 and 3 of the wall.
1:52 it held...for now. The next problem I faced when i beat this, was keeping my energy levels up in pace with my growing defensive needs. the creeper is your next significant problem since the blasters have pretty much got the drones under control at this point. At any rate, At this point I start trying to move my shield wall away from the LS to give me space for additional reactors, and as the height grows, i use repulsors to hold the creeper away from the shields up top, and before long switch to using repulsors and launchers to hold creeper at the bottom while the blasters only worry about drones. if things fall behind I can always switch a blaster over to drones then creeper for a bit.
2:05, I have most of my shielding replaced and can start to remove back rows to free space for reactors, Im also beginning to put down some tech domes. not always necessary, but i found, late I might add, I needed reactor upgrades along the way to keep up energy wise. First time I beat it I removed reactors to build these wasting 30 energy, and the last 6 reactors i put down weren't old enough to have made that much back yet, so it was a net loss. This time im building them in the hopes of getting ahead on my energy in time. Note that I kept two shields thick at the bottom two levels right up until I discarded my shield walls entirely with the fall of the first emitter, sometimes you have leakers, and its best to not let through when it likely means a hole the creeper will also get in through.
3:37, I've progressed a bit, My defences are near full height, I have my blasters on drones only, repulsors holding my lines, and a launcher killing from the bottom, with another going in up top. i also have enough tech at this point to grab the first energy upgrade, and unlike my first play through, am not running a constant deficit that forces me to cycle units connected/disconnected to keep everything operating. Im actually holding a small reserve at the moment....Time for 2 more blasters to defend the top of my defences from drones, and after those, a few more launchers to push back my only real issue at the moment, creeper.
4:57 stable, holding my ground, and ready to start moving the LS back leftwards, I drop a beacon to hold the territory, and two ore rigs in preparation of an advance.
6:03, i've advanced far enough to reclaim the little pit to the left of the starting point. And the creeper isn't as tall a mass as before, ground is being gained, but im also running constant deficit, fortunately, its not a fatal deficit.
8:09, Wheatmidge is done by this point, im just getting a nullifier up and in place. I had one already, and it hit zero seconds, but the shield broke just a few frames before it tripped so that was a failure or I'd have already pushed past this point.
9:13, the first gateway falls, now its a snowball effect, as the creeper is fully under control, and the drones aren't enough to punch through my lines.
11:42 the creeper is in full retreat, the drones are no longer an issue, they died a minute ago, the last emitter is coming into reach, and the last bonus item is being collected. Alas it won't get me second place, mopa42 finished at this point, i still need another minute or so. Still its far better than my initial 19 minute run.
12:03, the last emitter falls, and thats that. success at 12 min 6.1 seconds. I might have done it a bit faster if I also used my repulsors i had, but I find it very tedious to keep everything in motion, and was busy enough with this post
The forum was being a tad cranky about my posting them all, despite fitting within the limits, so instead i've included only the key images, the rest are found here:screenshot gallery
Hope it helps.