For your second jam, this is unbelievable. Its crazy good. The gameplay felt good. It wasn't too hard. There's replay value. There isn't even any big things that I could suggest.
All that aside, my main problem isn't with the game, its with the downloadable .rar file. To be able to extract and play the game, I had to look all over the internet to figure our how to extract it. Ignoring that, the only suggestion that I have is adding some more particles/effects. I think that would add a lot more impact when you shoot/blow up boxes.
All in all. You have a great game. Really well done! :)