Your piece is very relaxing. It has a very consistent feel to it.
On the other hand, it does have an improvised feel (I understand from the description that it was at least partially improvised) and does not seem to include any repeating themes (except perhaps the bass progression? It was hard to tell). Unfortunately what this amounts to is that your piece feels much like you are just noodling, which I am guessing you were, to some extent. Since you are using a pentatonic scale, and almost randomly, there aren't any strong harmonic progressions and therefore the notes don't lead anywhere, they really could just go anywhere (and end up doing so). Where the piece ends, there's nothing that tells the listener "oh this is the ending" or even "oh this is something different". Same thing for the beginning--you kind of have one consistent flow, almost like stepping onto a strange planet for two minutes with no goal, no purpose, all there is to do is simply look around and observe. I am not sure if that is what you were going for or not.
I would suggest spending more time on your pieces (half an hour is not a long time at all). Also I would suggest dedicating more time to establishing coherent ideas. That is not to suggest this piece is bad. It is easy listening. If that was your intention, then congratulations! If you had a particular idea as to what you wanted to accomplish with this piece, perhaps you could tell us. This might help with providing suggestions.
Hope this helps!