Inside is an astounding piece of digital art combined with a mediocre game. Almost all of the fun comes from enjoying the sights and the atmospere. And there are a lot of sights. The environments and characters are crafted with such meticulous precision, that you often have to stop and stare at the screen with your mouth open. It's a miracle what the developers were able to do with Unity and how smoothly the whole thing runs.
As for the gameplay, your main task is running right, sometimes with a few twists, until you reach the next simplistic puzzle and repeat. It's worth noting that the running parts take significant amount of time and there are passages where you need to hold the right arrow/button for more than 40 seconds straight without having to press anything else.
The story starts out promising, with subtle hints at what's going on in the dystopian world, but then, after 3 or 4 hours, you reach the end and realize, that the hints were all you were going to get. I found the conclusion unsatisfying and was left a bit disappointed, yet impressed by the insane attention to detail.