You're game is Great. The detail :
+ You take the risk to use an idea that BTP talk about in this video, but you manage to make it your own way, congratulation.
+ The game is looking good, very cute.
+ Music is great too (but (I quibble ) not sure it's the most appropriate with this game genre)
+ Controls are good
+ Level design makes the sequence of levels fluid
+ Tutorial part is simple and efficient (I'm jealous)
+ Death is not punitive
- A bit repetitive
- One obvious strategy : carry only one package at a time
- Need some incentive to optimize your delivery
- A bit laggy on my PC.