The alpha build in this thread is outdated by five months. There is a more recent demo available free of charge:
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I finished both (the outdated alpha build and the demo).
In the case somebody is curious, if you collect all orbs in the first level, you get to unlock a door in the beetle room. In that room, you get to see an artwork by "Aster Effect" of DeviantArt.com.
Edit: If you collect all orbs in the second level (boss chase) and never lose, you get to collect Mau's memory near the end.