This song is freakin' cute! I like it ^^ Works really well!
It's very minimalistic, but that's it's strong point in this case. You've done a good job with making a repetetive melody interesting. You've got the structure nailed as well, by adding instruments and small changes the song stays interesting.
The bridge part at 01:29 is also very nice, and I really like the change you go for at 01:42. From slightly sinister and exciting to light and cheery. Seriously, that contrast makes the 01:42 part so much more bright and uplifting!
I probably don't have anything bad to say about this song, what it strives to achieve it does achieve. So nice work :)
Also, if you have trouble with looping, just send me a PM and I'll probably be able to give you some advice.