Finally found the time to play my physical copy of this game - and I had a lot of fun for two consecutive evenings!

It's a very competent top-down (at some points sidescrolling) Metroidvania/Zelda-tribute, with nice-looking and clearly distinguishable pixelgraphics and great music, though I felt sound effects to be a bit lacking in comparison, but thats a minor nitpick.
The music is really good, though, and accompanies the (three) major areas very well, but I found the looping a bit too short for the amount of time one spends in the areas :)

Graphics are more resembling a Zelda game as, after a nicely done action sequence in lieu of an intro, we are looking down on our space-lady, and finding our weapon in a stone lodged in the middle of a (kind of) wood-clearing is somewhat telltale.
Using that weapon we can now easily defeat the (relatively few and never respawning) enemies and open up no areas to explore for even more new gadgets, while we collect the energy for our spaceship to launch again.

This is surprisingly complex (considering it's an Indie-release) and a tremendous amount of fun.

The difficulty is ... negligible. The (automatic) saves remove any penalty for dying, in the worst case one has to redo a couple of screens. In the sidescrolling areas an immediate restart allows quickly retrying the (relatively) short sequences without much trouble. The few enemies are easily disposed of (with the exception of the bosses), so the adventure aspect is clearly predominant, which I did not mind at all.

A particularly nice touch was the area-introductions with little fly-over intro sequences and the intros (and outros) of the bosses.
The savegame feature is also a very good addition, as it allows you to save basically whenever you can quickly reach the spaceship or when collecting any item.

And as with any other good metroidvania game, the upgrades and gimmicks are fun to collect and seeing early dead-ends while knowing that one will be able to pass them surely later on, motivates tremendously.

So Oni is a great timesink for the couple of hours it lasts!

I did have some bugs occuring, specifically later on once the jetpack is available: My sprite would vanish from the screen occasionally when activating the jetpack and I couldn't go on. Fortunately, the automatic saves made sure this was not a tremendous cause for frustration, though.

All in all, a great game!