What are the secret achievements in Machineers?

I have completed the main story mode of Machineers, earning an achievement (Google Play Games) for each puzzle, but there were still 5 secret achievements left. After a bit of poking around and trying alternative solutions, I managed to snatch two of them: "The tank" and "Ruby's birthday". These are fairly straightforward and their titles are good clues as to where to find them, but in any case, if you are reading this and would like some hints, I'll gladly tell about them. For the other three I only managed to learn their titles and the puzzles they can be earned in:

Landing Lights - found in Lorry's Oil puzzle.
The Safest Course of Action - found in the Train Tracks puzzle.
Efficient Invasion - In the Intruders puzzle, getting the aliens to move using the smallest number of parts.

For 1. I tried making the letters scroll by one by one from left to right, and scrolling from the two ends towards the middle, but none of these were what the developers thought.

For 2. I have yet no idea, but will keep on plucking at it.

And for 3. I have a solution that uses the trivial parts outside the main logics box, and only 2 belts + 1 gear in the main logics. Yet this is still not enough (or maybe I have some other error in there?)