Yay! 
Alright, here's some unsolicited play test feedback. I love the game, but here are some suggestions: :-)
The "reveal all secrets" upgrade is great, but it can lock you out of completing some levels. For instance, the opals in Melon cannot be grabbed anymore. It should be possible to turn this ability off.
Maybe related to that(?): it's literally impossible to grab the blue key in Zurich. This is quite annoying, since it was really hard to already get to that point.
Why are there lives? The only thing it does is forcing you to go through a few more screens to retry, once you're out of lives, which is slightly annoying. It doesn't seem to add anything to the game.
At the start of the game, the fact that pushing sometimes doesn't work at all feels like an annoying bug. Now I know that this is solved soon enough, but still, it might turn players off of the game. Maybe make the push always work, but with some delay?
Why are there no level names in Wonderland? I miss that. There are some great levels, but without names they're forgettable.
The first level in Wonderland is quite hard, it required quite some planning and practice. On the other hand, I passed the levels after it in one attempt. I'm not sure if this is great, since this one hard level locks you out of the whole world. (The same holds for Melon by the way, which is also quite hard.)
The alt key for placing bombs is weird. I would suggest X or Z.
Cube is too big! Exploring it fully takes hours, even when making a map and almost never making a mistake, because there are so many doors that lead back to the start, and you only know when you go through them. I would suggest keeping the same amount of rooms, but removing some of these useless doors: some rooms should only have two exits.
Maybe this is just me, but I find the sound of many gem drops annoying. They use musical scale tones, but I believe they are chromatic (half tones), not from a scale like a major scale, and the melodies they make certainly don't end at the root note. I would suggest sticking to major scale tones (which should be easy), and if possible, always end on the root note (though I realize this is hard to program). This way, they will generate pleasant melodies.
I still cannot finish Ghost in the Shell... Maybe I'm missing something, but even 150s seems very tight.
Why is New York twice in the list of levels?
There are many great levels, but here are the ones I loved the most, despite taking quite a few attempts:
-Weir
-Atlantis
-Great Hall
-Five (though it is really hard!)
-Beijing
-1010
-Swarm
Hey, thank you for your critics, I appreciate that.
First of all I have to say, I'm a hobby-game-dev not a professional. So I think this might answer some of your questions already ;-)
I started this for and with my son, just to have fun. Then I got pulled in more and more and the idea of creating a whole game out of it, with upgrades and stuff didn't let go anymore.
The partial lack of a consistent growing difficulty level as well as some conceptual bugs or even wierd sound effects are surely related to the fact that I dont have mutch experience in game development.
I learning a lot here... :-)
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"The "reveal all secrets" upgrade..."
Yes, if I think about this, it seems to be in fact a conceptional bug. I apparently never tested this caves with the "reveal all secrets" upgrade.
The possibility to switch the upgrades on/off would realy solve this and would also be a benefit and additional user freedom. Will check this for a next update.
"Why are there lives?"
"At the start of the game, the fact that pushing sometimes doesn't work..."
When a started with creating the game, I wanted to stick closely to the original Boulder Dash from C64 that had lives as well as the unpredictable push success of rocks.
But you are right the lives does not make a lot of sence anymore since the game evolved and with the possibility to restart every cave.
"Why are there no level names in Wonderland?"
"The first level in Wonderland is quite hard..."
Wonderland is weird stuff and I simply got tired to come up with new names for every cave :-)
"The alt key for placing bombs is weird. I would suggest X or Z."
Right. I moslty played the game with the gamepad, but for my next game I will make that customizable.
"Cube is too big!"
Yes this is certainly too mutch.
"I find the sound of many gem drops annoying"
Sound and sound effects are realy not my thing. I got the gem drop sounds from some original SID sounds but played around with them (for the worse I suppose)
"I still cannot finish Ghost in the Shell..."
Hmm honestly, I have to replay this first some day, to be able to gave a propper answer here.
"Why is New York twice in the list of levels?"
I realy thought I had corrected this before launch. But if it is still there twice, it is a bug.
Hope this answers some of your questions and thanks again for your great feedback!