This was a bit of a mixed bag, but I spent by far the most time with it out of the games I've rated during this LD.
The gameplay was fine. It took a bit of figuring out, but it did keep me sucked in for a while and was pretty fun. The game definitely had a survival mood around it. Finding 14 Dark Shards is perhaps a bit of an overkill, especially with how much scrap the miners require.
Unfortunately, I was close to getting 14 shards but accidentally placed a miner inside of myself. This rendered my character immobile and my only chance was for an enemy to come from a direction that would conveniently destroy the miner before myself. Being able to remove existing structures should be on top of the future development priorities.
Other bugs I found involved using an emitter's "place" mode to provide perpetual light whereever I went, as well as being able to place multiple miners on top of each other. That was fun.
The game over screen was great, but I found no way to return to the main menu afterwards.
There could be use for more enemy types as well as improved graphics and audio... However, I understand that these weren't your focus. On the other hand, I have to raise my hat for using your own engine, especially one with what I assume to be Java! The game systems themselves worked fine, and I liked that objects can have a lot of different types of information they can display when clicked.
Overall, a solid experience; despite the flaws, this was one of the most engaging compo games I played so far. Reminds me a bit of games such as Notrium. Good work!