There's a whole lot of good in this.
Like others, I think the polish, like level transitions, is so cool. The sounds and facial expressions make me feel like I'm flinging real-life monke's around, which is awesome.
It's a really interesting line to walk between frustration and fun and I think this does a good job playing with that line (especially for a jam). Like you said in other comments, I did find it unclear if I'm flinging / letting of stuff at times. Adding clarity for that would probably go a long way. The banna grab + happy face at the end are such a nice reward for making it through.
Agreed with @Itizso that having a save + continue feature would also add a lot. :)