Really cool! Such a simple idea, yet a very interesting and challenging puzzler!
There's not much going on with the aesthetics, yet you've made it all look well rounded and nothing stands out as off. The "mine" theme of the artwork is very neat!
Shame there isn't any sound or music, but not really a deal breaker in my opinion.
My only criticism would be about the controls, which are a bit hard to get your head around. I really like the 90 degrees perspective, but I think having the controls mapped according an always indicated "north" of the map (up is north, right is east, etc.) instead of the camera angle would help a lot, especially with the rotating camera. In the current state I found I was never 100% sure what direction the cubs was going to go.
But otherwise, well done, quite an elegant game overall.