Well, I've just completed this game in about 5 hours total on lunchbreaks, and frankly, I don't see what the excited reviewers are talking about.
The game is way too short.
It's a game with 3 levels and one shop overworld area. That's it. Once you complete it, I don't see why you'd bother replaying it, there's no multiplayer or even some cool New Game + mode, although upon completing the game it teases you with a "new" looking main character.
Unfortunately, it's also WAY too easy.
The enemies are laughable. Even the potentially dangerous kamikaze robots leave powerups behind, so basically, even if a kamikaze targets you, there's a 33% chance you'll just get your life back in a powerup. Come on... The rest of the enemies are basically a joke, a nuisance at best.
The laser traps are quite deadly but aren't ever used in a way that leaves you puzzled.
That's actually the problem with the entire game, there's no real puzzle element at all.
The only "puzzling" you'll see is poking around for a tile (Zelda bombable walls style) to break and reach a secret area.
The spelunking mechanic, while addictive and cool in theory, is actually quite shallow. It might seem like digging your way down efficiently requires effort but it really doesn't. If you can put two and two together, you'll figure out how to dig the mine properly in 10 minutes.
Finding treasures? Not only is it easy enough initially, you eventually pick up a powerup that just displays every single treasure on the map, pretty much turning your exploring into running through a checklist, so yeah, a chore instead of a challenge.
Oh yeah, and the story? Well there isn't one. You jump into a mine built by your uncle or something and everyone is like oooh, what could be there... And then you finally stumble upon a menacing area that looks like something out of Metroid and you finally think oooh... some depth in the story finally? But nope, the final boss is some random-♥♥♥ contraption named Vectron or whatever, you beat it and you're supposedly assimilated with a new technology, and you get the main menu...
Seriously, I'd rather have this game be entirely abstract than have this lazy-♥♥♥ attempt at a story that tries to put steampunk and futurism together in the most vanilla way possible.
Anyway... My personal rating would be 5/10 as in absolutely mediocre and not really worth your money.