". . . I simply want to test myself by listening to a song, and then trying to come up with my own arrangement, using my own style."
I had to go back up the thread a bit to remind myself what the objectives are with this devilishly simple-looking project. I think you have passed the test. Nicely, at that. But I kinda wonder about the relevance of the 30 second limit. Your interpretations are good, but just seem rushed in some cases. What about a 40 second limit? Or maybe ~35 +/- seconds. You could call it a relativistic 30 seconds. Realistically speaking though, nailing down an interpetation of a tune, even a 30 second (+/-) tune, in one day is no small feat. Eight in fourteen days is pretty amazing.
Keep on -ing