I clicked on this game because it had pictures of cute slimes, and I was not disappointed with the content!
It's simple while remaining fun. It does get repetitive when there isn't a new mechanic or idea between two concurrent levels. The shy purple slimes are a nice concept, there could be an opposite type: a slime which only makes friends with another currently friendless slime, for example. As it is, the game doesn't overstay its welcome, even with 20 levels.
I like the graphics, the music and the sounds. I do like that the slimes move around the screen, that makes the interactions far more interesting than if they were simply sitting around. However, the size of the UI does hide the hearts for some wandering slimes, especially in the final level I found that two yellow slimes spent a lot of time wandering around beneath the instruction box at the top.