Forts

http://www.earthworkgames.com/

The only thing more fun than building a ramshackle fort is smashing someone else’s. Physics-based building underpins a race to research tech, build weapons and open fire on your opponent.

Genre: Real-time strategy.
Platforms: PC.
Difficulty: Not super hard, but expect to replay levels. Human opponents may be very challenging.
Content: As well as a single player campaign, you can play against others online. Be aware of chat options, if this is an issue.
Age-related suggestions: This could be frustrating for younger players as structures can be fragile and prone to falling over.

Consider consulting detailed reviews before purchase.