Nice, cute and clean visuals. Music worked pretty well too. Obviously would have needed some sound effects and more polish on the visual side as well.
As already stated by others, getting a full on game over and having to just go grab all the stuff again was kinda tedious. Like if I jump to the water in the beginning it's fine but if I fall there with the balloon it's game over. Didn't quite make sense.
Could have used some more hints on what could be built in game. Only things I found out how to build were the balloon and the turtle taxi. The hints you had there like the string can only join two objects together were along the right line but not really that helpful. Of course I was trying to join two things together with the string but if I didn't have the exact right ones the game was like "nope, those aren't objects, try using objects next time newb". First I made a balloon (without the feather) and you kinda gave away that I'll need to add the feather next time.
After few failed landings with the balloon (WASD controls were for some reason inverted when flying, arrows weren't), I experimented more with crafting and managed to build the turtle cab. And with that, I sailed on... for what felt like an eternity. After I was just about to give up, I saw the island. And then it just went past it. After that, insert another eternity and almost giving up again and I see another island, sweet. Except didn't find any way to get there and the turtle was just stuck on place there. Was I supposed to do something there to get to the island, nothing seemed to do anything.
Knowing that the islands were there, I built another balloon and went on my way towards them. Then I tried to land on the island and the squirrel crashed and died. This was the time I decided to call it quits...
Anyways, good job. As you and others have already discussed, it might have been a tad too ambitious so you couldn't really focus on the most important bits, the gameplay and final polish. Oh well, jams are all about the learning experience anyway so next time you'll know!