Given the right setting, curiosity can be all the motivation you need to be drawn into a game world. Forget map markers and quest icons, all you really need is a world that compels you to keep moving deeper inside it. That was the simple idea that drove games like Journey and Proteus and even Minecraft, and it's the same primal instinct that's at the heart of Fract OSC. You proceed because you want to see what lies over the horizon, not because there's a carrot dangled in front of it.
There are elements of platform gaming and puzzle-solving here, but mostly Fract is about exploration. It drops you into a stark and surreal landscape with no explanation as to why you're there or what you need to do and then leaves you to it. What instruction there is comes in the opening area, which acts as a basic tutorial in how to manipulate objects in the environment. That done, you're whisked off to an even stranger place and left to your own devices.
Comparisons to Proteus may send up red flags for anyone not fully on board with the whole "art games" movement, but Fract is more obviously a video game in its design. The challenges you'll face are familiar at their core, but rendered peculiar by their context. How do you reach that interesting looking spot? What do you need to do to make this machine work? These are comforting reminders of objective-based play, but the game doesn't enforce them too strictly. The most interesting parts of the world require you to engage more fully with its mysteries, but you can simply roam at will if you like.