I'm working on my first game, and taking the opportunity to brush up my C++ (I want to make as much of it as portable as I can.)

Whilst working on the technology tree and how it affects actors (spaceships, planets, crew, buildings, etc) I can't find a pattern that decouples these entities enough to feel like a clean approach.

Just as an idea, here's the type of effects these actors can have on one another (and techs too)

• An engineer inside a spaceship boosts its shield
• A hero in a spaceship in a fleet increases morale
• A technology improves spaceships' travel distance
• A building in a planet improves its production

The best I can come up with is the Observer pattern, and basically manage it more or less manually (when a crew member enters a spaceship, fire the event; when a new building is built in a planet, fire the event, etc etc.) but it seems to be too tightly coupled to me.

I would love to get some ideas about how to approach this better.