Wow! I'm in love with this game.

Honestly, it's a masterpiece. Just finished the levels on the penultimate planet, the first one where you find the pseudo-elements. Drove me nuts at times, but that feeling when you finally finish them and hear the tin-tin-tin-tin-tin sound of the compounds arriving to their destination at highest speed is indescribable.

Only final level left. Finished all levels including all the optional ones. Didn't manage to do all the challenges (below n cycles/reactors/symbols) but did manage some of those too, one without even trying to, and one in particular "Molecular Foundry on Haphaestus IV using 2 reactors" of which I'm particularly proud of.

I didn't google for video solutions to any level (except one of the very first ones on the first planet, but that was because I had no idea what I'm supposed to be doing; the tutorial is probably the only weak point of this game since you can still be confused even after reading it at the beginning). Some of my solutions were neat, solid ones. Some were ugly, but efficient. Some were ugly and inefficient. Some were unbalanced, relying on extremely long in-between-reactor pipes (and that would fail because of this in the long run) and some were so bad I was just happy to have the level over. But then there were also those few cases where you come up with an extremely clever and efficient solution and are happy to see it placed among the top in the charts.
I did improve some of my solutions for efficiency after finishing (I usually went for the least reactors, rather than least cycles or symbols), but didn't go out of my way to do it. In some cases I had an idea for a more efficient solution, but it would require redoing a lot of my code from scratch, so I just left it.

And then there are of course the times when you're pulling your hair "Gaaah I'd have the perfect solution if only there was one additional column on top or if I could put 2 symbols on this one square".

And after finishing a level, I'd sometimes watch youtube videos out of curiosity just to see how it could have been made more efficient. Or how on earth did someone finish it with 1 reactor. Wow, some of those were simply amazing. Makes me realize that although human stupidity never ceases to amaze me, neither does human ingenuity.

As a cherry on top, it has an excellent, very well written story; something you don't always see in indie or puzzle games.

So, if you have this game but haven't played it yet, go ahead and give it a try. I really recommend it.

It is a really good game, I didn't get far into though before it got too hard...

I agree that some of the solutions people come up with are pretty incredible, I looked up a level or two when I got stuck and was amazed by how much quicker and simpler other people's solutions could be.

It's also available really cheap during sales (I picked it up for £0.69 or something, and basically bought it purely for the price and because it sounded a little interesting)

Yes, thanks. I meant to add that. It's very often on sale so you can get it for cheap.

I played it and liked it too, tough I did not finish it (Im going to do it when I have more free time ). Do you have any suggestions for any other games similar to this, that force you to use your brain?

Try Sokobond, if you haven't already. It's not "programming" like SpaceChem, but I really loved the puzzles.

There is also TIS-100 from the creators of SpaceChem, but I haven't tried it.

Do you have and/or have you played Shenzhen I/O?

It's an amazing game. If I got to pick just 5 games to keep from entire GOG catalogue, SpaceChem would be one of them. As far as I know Infinifactory from the same author is based on the same principle, but in 3D environment, so it should provide a familiar experience with an extra layer of complexity.

Thanks ZFR and Densetsu for the recommendations. I will be looking forward to buy Sokobond and Infinifactory, but only just AFTER I will beat SpaceChem.

I love programming games, and Zachtronics are the masters of the genre.

So far, SpaceChem, TIS-100, Infinifactory and Shenzhen I/O have been mentioned (all of them from Zachtronics, I believe), so let me throw a little love in the direction of Human Resource Machine. It is also very very good, so if any of you like some of the Zachtronics games, do consider having a look at Human Resource Machine. It's from Tomorrow Corporation rather than Zachtronics, so the style is somewhat different, but it is just as good. It is basically assembler programming, but with a graphical interface that shows what the code does in a very visual way. The game isn't all that long, but the puzzles are interesting, and the style of the game is quite funny.

I have both SpaceChem and TIS-100 sitting on my shelf.

They intimidate me.

Yeah, I can second that recommendation. Human Resource Factory is kind of an easier version of the same kind of concepts I would say, a bit of a more gentle introduction if you're not familiar with the programmingy style of the games.
Just played through it recently.

TIS-100 is probably my favourite of the bunch so far, though I've yet to play Shenzhen.

And... finished it.

The last level was annoying. I spent way too much time trying to execute the solution after building it. Required way too much micromanagement.
Don't get me wrong, I liked the defense missions, with the on/off controls but in this case there were just too many little things to take care of. And the meteors had the habit of appearing at the wrong place at the wrong time.

Still, this was a great game. And finished just in time, since I'm leaving on holidays tomorrow. There is still the 63 Corvi DLC to do after I'm back.

I do have one question about the story ending though. If anyone finished the game and can help me, check this thread:
(Warning ENDING SPOILERS! So don't click if you haven't finished the game)
https://www.gog.com/forum/spacechem/ending_question_ending_spoilers