Not bad
Not bad at all, although a tempo change doesn't really count as a time signature change, I'll let that go.
My biggest critique here is the song is rather simple. But aside from that, it does do a pretty good job changing the mood throughout, especially when contrasting the middle bit with the end.
The bass part throughout is pretty unique and gives off a different kind of vibe, which is a nice change from most peoples use of the common 4 note bass line.
Keep it up!