This animation has shown how much you have improved and you seemed to be getting better not just in the designs(simple yet well done) but also adding music to the otherwise silent and dull animation(an animator's skill.)Though the ending is a little sudden,this is just a trailer(is it?) and not the 'real thing',so not much can be expected yet.Just keep practicing on the designs(try moving onto more difficult types like characters with human/animal features,for example),the plot(if there is going to be one in your project,an original idea is the best) and voiceacting(if there is.)
Good work on this and hope to see that project!

Hah! It smiled me! :)
Nice.