Very cute and well presented! I like the idea and the art a lot! I felt sad when my slimes were eaten :(... but good evocation!
To echo another comment, I did have a couple small issues:
1. A lot of lag on respawn; probably just the number of entities
2. Once the "next slime" had slid off its branch, so passing it didn't actually make progress!
3. I wasn't sure if there was a choice or pattern involved in passing them... it seems like there isn't, but if you work on this more that would be really cool!