I'm not too fond of the mines being so close on the left, though. Try working on your tilesets next time to make your maps more visually appealing. Like geti, I started off with some terrible maps, aswell.

good, this is a solid 3.5 up from me, some of the mines felt a little rushed, and double gauss isnt always a good idea in close quarters, but you cultivated the mood in this level well. i'd suggest making some more interesting shapes (especially for example, stray away from the 4 tiles around a 1 tile wide tunnel in most cases. it can be used well, and didnt detract from the mood here, but having identical sides to a tunnel is usually a bad idea.
i liked how the homing drone was potentially very persistent, and i loved the jump in-between those mines, but try to keep it flowing, and all in one style. there were a few areas that prevented me from actually perceiving this as a "4", but its definitely a much better map than you have been making. it has direction, and a theme (albiet a tad bland in that regard), and i liked how some areas were kept angular (the corners of the "box" in the middle), and the line of 5 tiles was nice as well, i thought you might pick up on my like of them :P
try to keep your object themes more consistent though, and keep looking at good maps for inspiration. also, perhaps pop onto the forums and search for atob's commentary on "function and form", it has some good theory in it.
also, have a look at my beginning maps (the first ones in my profile), and consider that those are from after i deleted most of my maps to start afresh.

im 16, but started mapping when i was about 12. for my first half year or so i made some awful maps though XD
im playing this now, ill come back with some critique.