Finally done !
I must stop here, so there will be only 11 levels. Most of them are a bit too easy and more graphical than a real challenge though.
Without a level editor, making those levels took me more time than I thought (~1h per level: 30 min to design, 15 min to code, 15min to test & debug).
I removed all restrictions I added on Zip (air control), it didn’t add anything useful to the game.

The most difficult level in the end was the most unexpected :

Some others were more difficult to design/code and less fun :

So in the end, it was a really interesting experience

The final “2-day Ludum Dare competition” will remain available here, I won’t edit this version any further:
http://www.teradem.net/HTML5/Zip/

Have fun !