Easily in my Top 5 regarding fun.
Adding a new challenge each stage by introducing a new animal was rewarding and the overall rise of the difficulty was well done.
I would have liked an indicator when a new enemy will spawn and which connection opens which path. It was a bit frustrating going one way just to connect to the wrong one.
Also sometines it was hard to see if a "crossing" could be done or not.
But given the level size, resetting was fast enough to net get frustrated, so it didn't break the enjoyment.