Nice melody line, and base notes.
I know it's an atmospheric piece, and its supposed to be simple, but a little extra details can improve this song big time (may i suggest subtle background sounds).
It's has all the potential, keep going !
I really like the mood you made with this song!
Two things I think you could improve:
1.There are points where the bass is playing two notes at the same time because of some overlap, creating some out of tune beats in the lower frequencies, which can be overwhelming and undesirable. The plucked guitar also gets a bit low at times, and clashes with the bass, especially when only playing off by a half step (the dissonance would be ok if the guitar was up an octave).
2. You might want to vary the arrangement at some point to add some more interest. Maybe adding another instrument, or changing the harmonic rhythm, or using some different rhythms in the bass.
Overall a very nice little piece with a real sense of atmosphere.