While this is a good song in general, it's not particularly my cup of tea. Since this was entered in a contest, I'll review you in my own personal opinion and through the eyes of the contest judges.
The mixing is really quite good, although it is very repetitive, you did a great job building this song, I didn't hear any bad notes, save one or maybe two. So not bad at all.
Contest-wise, this could either be a hit or miss. In my eyes you could write a song about a biodome in two ways. One, what you did, with the safe and happy feeling. Or, two (I woulda done this one) make it a bit spacey, and safe-ish sounding, but add a creepy, eerie sense of mystery with a slight tinge of fear of the outside. If I were judging, I would prefer the latter, but hey, you never know.
Good luck.