If you've ever played 'Tea for God' or 'Unseen Diplomacy', then you understand how they do the locomotion. For everyone else, the game relies on your play space size and then changes the geometry of the level so you never have to leave it. You just walk in little twists and turns to get around. It's awesome.
That said, you do need a larger play space to be effective. I had a 2mx2m and it worked great but 3mx3m seems to be ideal. For smaller spaces, it will shift the world toward you as you move, meaning you cover more ground in less area, but it also create a wobbly, swimmy feel that might make you sick. Just a heads up.
The game itself is really well done with creating a horror atmosphere without relying on purely jump scares. There is one at the very end though so be aware :)
The graphics are amazing and oh yeah, the game is totally free! Check it out!