Suggestion/ideas
Readability!!!
* Color & buildings: Even if I like the idea that everything is of your colour, it is very hard to read your territory. It is also hard to read if a mountain is settled or not.
* Buildings all the same: With a bit of dezoom, all the building look the same, not possible to quickly differentiate university from village. The shape/size and secondary color shall be quickly recognizable.
* Unit barely differ from another visually: not possible to recognize cavalry from horse archers with dezoom. One way to easily handle this maybe to have several miniatures to represent a single unit, for instance infantry is made of 3 miniature, and an archery of 2.
UI:
* Units hard to select, and ironically, hard to spawn a unit on an occupied territory sometimes
* Unclear if ranged unit or 2 moves units already attacked.
* What is the third characteristics of the units?
Improvement of the game as it is:
* Sacrifice units, to free population limit
* Handicap/Bonus system for a player/AI (ressource % or starting hex)
* You shall not need to kill all mine & port to win
* Upgrade for cannons!
* Allow to make roads over mountains, which only connect 2 of the neighboring hexes.
* Allow to simultaneously swap 2 neighboring units at the cost of one move for each, this will make your cannons definitely more valuables.
Concept to change the game :
* Linear upgrades: it is usually not very critical which upgrade you take because you always do the same at the end (If I think infantry man is the best, I will rush their upgrades). It is better to offer choices which allow to counter the enemy strategy: you do mass infantrymen? I will have an upgrade which allow my horsemen to attack before your infantrymen move.
* More upgrades, with incremental prices (e.g. Infantry attack 1: 10 coins, 2: 25 coins, 3: 100 coins, ...), so you cannot have them all, and decide the one you want to have
* Some Terrains may influence fight, so that you can have more strategic depth. Example: doubled defence in the wood.
* Limit the overspawn of cheap unit? this make the cannon more interessant. => for instance unit which just died still count in limit.
* A capital city, buildings/territory not connected to the territory embedding capital not produce?
* Capture enemy buildings?
* Unique civilisations? With different voices language, as per Age of Empires!
* Co-op, alliance? => can my units travels through my ally territory? I recommend
* Units which produce bonuses to neighboring unit?
Game mode: (as per your other post):
* scored (terrain, ressource, units, ... customisable what bring how much point), after a certain amount of round come automatically to an end.
* Allow to combine all several game mode, you may have flags AND king.