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The shadow enemies aggro only if you look at them, which is hinted at with messages telling to be careful about your gaze right at the start of the part where you first meet those enemies!
The game in it's current state is not a demo, but a finished story, so far I can confidently say that it will get a steam release in the coming months with a bit of additional content for a small price (Arena wave survival mode is the main addition). But that's for now it in terms of continuation.