Wow, so quiet! Took me some time to understand what to do but it seems I enjoy working, transfering messages for strangers :-)
The level design is really nice and I liked how you used the notes to explain the game.
Two things I'd have changed.
1- Allow to see the target while operating a system (maybe a button to get into "aim" mode and then WASD to actually aim?).
2- Allow to climb from further away.
Great game!