Block squares of an opponent's city

Unfortunately, progress with Settle the World is very slow at the moment.
However, there has been a little progress in my development version.

It is now possible to besiege another city with military units.

If a player places his combat units on fields that are being managed by another player's city, the city no longer receives resources from these occupied fields.
This works with military land units as well as with warships.

If a player blocks the production of food for another player, this can quickly lead to famine in the affected city.
The affected fields are outlined in red in the city view.

If the military unit blocking the field is moved away, production can continue as normal on the previously occupied fields. The player does not need to take any action here.

This functionality is of course inspired by the games Colonization and Civilization ;-)
And it will be important on my way to create a computer controlled opponent.