Fun game! There are so many games out there with this 'linked characters' mechanic, so it's refreshing to see something that basically puts a twist on that!
The execution of the spring mechanic is very good, it feels very real and bouncy and stubborn like any spring would. It's nice you let the player counter balance the restrictions of the spring by allowing the slimes to stick! Though I found that in some places it would have been useful to also be able to stick to walls, especially for those really high walls, or those first spikes – they really stumped me and I couldn't find a way through!
I did manage to stick to thin air though at some point! :D
The music is perfect for this game, it's cute, light-hearted and a bit goofy too, which is exactly how it felt playing these two adorable slimes.
Oh and props to giving how-to-play instruction straight after running the game, directly in the game itself. A how-to-play menu is nice, but I find what you did much more elegant.
Well done overall!