Embarrassingly enough, I couldn't even beat the demo when I tried a few months ago. I got stuck on the double bonds puzzles. Now that I have the full game I thought I'd go back and give it a go.
I deleted my saves and started again, paid close attention to the tutorial, and beat the double bonds puzzles in a matter of minutes.
Then I went on to beat the next few very quickly and I'm now onto multi-reactor puzzles at last!
It turns out I was trying much too complex solutions for the double bonds puzzle. I kept it simple and ended up using far fewer cycles and symbols than the average player according to the leaderboards.
Now I can get on with enjoying the game! \o/
I deleted my saves and started again, paid close attention to the tutorial, and beat the double bonds puzzles in a matter of minutes.

It turns out I was trying much too complex solutions for the double bonds puzzle. I kept it simple and ended up using far fewer cycles and symbols than the average player according to the leaderboards.
Now I can get on with enjoying the game! \o/