This is a larger than normal update. I've added several features related to unexplored and unseen terrain.

New

For starters, both you and the enemy now begin with no knowledge of the map. This is represented by black squares:

As you move your tank around, the black squares are revealed. For instance, here we have found a nearby neutral city:

While you are exploring, the enemy is also exploring. Eventually you will find him (her? it?):

Finally, at the end of each round, you also see the amount of the map you have explored:

Postponed

I was also going to add a "visible" feature. That means you would explore to see landscape and cities, but you would only see enemy units if they were within your range of vision. The vision range is 1 square for tanks, 2 squares for cities.

For coding the AI, including "not visible" terrain is pretty easy. In fact the AI team in this release is using this method. This gives the AI worse knowledge than the human team, and puts the AI at a disadvantage.

For the human team, my idea  is to cover the explored-but-not-visible tile with a gray square, then draw a slightly transparent tank/city/terrain tile  over the gray tile. This gives a visual cue of what the human last saw on that tile. The gray plus transparency would give a fogged-looking version of the city, unit, or tile.

The complicated part for the human team UI is identifying the city, unit, or tile. The city and unit are a bit complicated but still doable. However to check the tile, I have to find the  tile corresponding to a tile map coordinate, find its tile map atlas image, and... oh I give up already. I'll revisit this again in the future.

For now I want to move onward to something else new and excigint. Specifically: I want to add a new unit type. Here goes!