Mechanic Idea: Buildable Terrain, such as Chinese City Walls

While working on civ balancing for my “high effort rage post” on Chinese DLC implementation, I managed to overcome the Farming yield problem by means of much lower Chinese taxation rates, however, I ran into another major problem.

This photo is an eroded section of the Nanjing city walls, dating from the Ming dynasty, not so megalithic as earlier sites, but still immense and noted for resisting WWII-era artillery for many days in late 1937.

Buildable Terrain: Chinese City Wall

There is one big problem in this game’s timeframe and fortifications, and that is Chinese walls.

Chepstow Castle with 6-meter walls is considered thick, and Borl Castle with 12-meter walls is an outlier. City walls peaked under the Roman Empire, often reaching 10m heights (commensurate with Chinese towns) but only 1.5-2.5m thicknesses. The Theodosian Walls of Constantinople were 4.5-6m thick at the base and 12m high for the thickest, tallest inner wall.

Shang dynasty Chinese city walls, 15th century BC, were about 20m thick at the base. The Qi state during the Warring States period had its capital of Linzi, established 859 BC, enclosed by walls of 20-43m thickness. These walls would be about 10-15m tall for most major cities (I only found the number for Handan’s walls which would convert to 15m tall). Ming prefectural and provincial capital walls were 10-20m thick at the base, and 5-10m thick at the top, and these were mostly newly built since the Mongols had demolished city walls throughout most of northern China during the Yuan. The rammed-earth cores of Chinese city walls were also extremely effective at absorbing the energy of artillery impacts, and their design even resists all reasonable sapping attempts that don’t involve a lot of explosives. As in… a 10m tall trapezoidal cross-section wall collapsed down by 2m, to give 8m tall trapezoidal cross-section barrier, wow, such a big deal!

The editor only allows cliffs to be placed in 3x3 sub-grids of the map, which is also why the map edge sizes are normally always multiples of 3. As I envision them, Chinese City Walls can only be built on these same 3x3 positions that cliffs are arranged by.

This would be the first “buildable terrain” in the game. It cannot be Delete-demolished, and repair can only be done by auto-repair (from idle villagers finding work) or by the Repair command, otherwise they will simply walk on it if your right-click on its surface. Units may move onto/through the wall (which counts as higher elevation when shooting off it) via any unlocked gate adjacent to the wall—Gates gain the auto-lock option (i.e. when enemies approach) when built next to a Chinese City Wall. Siege Towers will deposit troops directly onto the wall when instructed to target the wall. Towers (and only towers) may be built on top of the wall and gain +1 range and +3 vision when thus constructed. If you build or have these walls, pay attention that the enemy doesn’t build a ramp (represented by a gate building) next to it and come rushing up your walls! The icon is normally found in row 3 slot 3 on the civilian buildings tab (Where Feitoria is for Portuguese, in case I need to use Row 1 slot 5 of military buildings for something else).

Now, considering some terrain like Kaifeng’s many waterways… City wall build permissions/variant checks may be ruled as below, with the idea that you cannot just wall off a huge bay, it can at most span a small river or bay mouth with two water gates. We know walls can transform because wall “towers” can turn into linear wall segments when you extend the wall. And linking two walls can cause both “towers” to vanish. However, this does not occur when you have two neighbouring wall “towers” next to each other, and you build another wall segment touching both of them. The game can clearly judge these proximity rules.

On at least one land tile: Buildable, becomes Water Gate 水门 if situated over at least 6 water tiles (modelled with visible portcullis arches on the two visible faces, passable to ships in all directions, may be locked against ship traffic)

On no land tiles but adjacent to a City Wall (but not Water Gate): Buildable, becomes a Terminus Tower, see Shanghai Pass’s Old Dragon Head for example. If you connect this to a City Wall on the other side, it will be remodelled into a Water Gate.

On no land tiles, between two City Walls or one City Wall and one Water Gate: Buildable, automatically becomes a Water Gate.

Adjacent to (i.e. between) only Water Gates or Terminus Towers and on no land tiles: Not buildable.

If destroyed, all units and on top take half HP damage and structures on top take 80% HP damage in the collapse (potentially fatal), and it is replaced by Chinese City Wall Ruins, which are indestructible and passable by units, but are unbuildable except rebuild or clearing away. The rebuild occurs by placing the same Chinese City Wall building on the ruins (NOT by right-click!) which will not remove the ruins until the building completes, and gives 50% refund on completion (if the construction is cancelled or fails, the Ruins are left untouched). Clearing occurs by mining the 10 stone value in the Ruins away, but Villagers work at a massive debuff in mining rate (something approaching 2% work efficiency, multiplicative AFTER all other calculations, so it takes as long to excavate as 500 regular stone would take to mine). Fishing Boats can also mine it away at a similar individual work speed, but will not carry any stone.

Once built, the Chinese City Wall DOES NOT OFFER VISION (we know this is possible with the AOE1 Blind Lame Priest unit), so you need to patrol it with units or place buildings along it (only Outposts and Towers can be built here, so no “walls on walls” to spot enemies. Attacker notifications still work, because the noise of trying to bring down the walls should draw attention, but if the enemy sneaks up and over unguarded walls, then they could just get in.

The properties of the Chinese City Wall should be something like so:

15000 base HP (upgradable by Masonry and Architecture), 20 stone / 120 seconds cost (mostly rammed earth, with stone outer facings, so it’s cheap but takes a lot of time), 150/150 melee/pierce armor (Trebuchets can still do some damage), same armor classes as Fortified Walls (so Standard Building, Building, Stone Defenses, and Walls and Gates) with 80% bonus damage resistance (Petards and Trebuchets can still do some damage, everything else just scratches).

I strongly advise you get yourself some siege towers for an assault, or suppress defenders using siege equipment, then build yourself a ramp (i.e. a Gate on your side of the City Wall) to continue the escalade, followed by another ramp on the other side that will let you across, instead of getting locked down by the enemy. Or distract the enemy elsewhere along the walls and suddenly storm a gate among a merchant convoy to force it open. Or you could just seize other parts of the map.

It REALLY is basically Buildable Terrain. In fact, if not for the “trying to breach the walls will make so much noise anyone would notice” problem, I would have it default to Gaia ownership (though repairable by all parties)!

What do you guys think of the idea of buildable terrain? The same item could simply be named something more neutral such as “colossal walls” for other civs to use. If the “other buildings” buttons were removed we could also use that space (row 3 slot 4) to implement buildable (and destructible) bridges in-game for all civs.

The aforementioned “high effort rage post” this idea would be used in may be found here:

So, after much consideration, I’ve come up with a solution for gatehouses that is more authentic than “slap a gate AKA ramp on each side of the wall and call it a day”, because going through the wall and up and over it are different.

First, remove the More Buildings button, the problem after adding Palisade Gates to AOE2HD is that the Civilian Buildings has 12 slots taken up out of 15 (13 for Portuguese with Feitorias), and Military buildings has 12 taken up out of 15 (only top right slot open).

Removing the More Buildings button leaves 2 slots open in each of civilian and military, freeing up more space for civ customization.

Chinese City Walls should be civilian as it’s neutral terrain once built, with anyone able to repair it or build on it, and not supplying vision to anyone. Under-attack alerts are sent out to all players with units within a certain radius (TBD) as it’s LOUD trying to dismantle these colossal walls.

Gatehouses are 3x3 military buildings, and when built in line with a City Wall or cliff automatically orient their passage tunnel (like other gates). When built alone they act as smaller fortifications. The access ramps on the Gatehouse (for foot units only, build a gate/ramp if you want to bring up cavalry or siege engines) can be determined for free and very quickly the first time after they are built (so that units don’t have to run past on top of other units passing below)), but remapping the access ramps or tunnel orientation afterward is very slow and costs some resources.

Gatehouses may be locked/unlocked (locking can be automated), filled/emptied. Once damaged enough, a locked gatehouse will transition to a Broken Gatehouse state which allows all units to pass, but can still fight until destroyed. A filled Gatehouse, however, will never transition to a Broken Gatehouse state, but filling the tunnels costs resources and is slow, while emptying is much slower and refunds only part of the resources spent. Broken Gatehouses cannot be filled. Broken Gatehouses can be distinguished visually by the huge doors being ajar and possibly thrown off their hinges to the sides of the entrance.

This means for enemies to get through one of these gates, a rapid assault by rams or petards is needed to break the gate down and let your forces through, or optimism by the enemy to not fill in the gate tunnels until it’s too late. The HP, armor and resistances of gatehouses are much lower than regular wall sections due to mechanical complexity being delicate, and if you destroy the garrison (visually shown by destruction of the actual gatehouse building over the gate) by damaging the gate enough (ascending the ramps to attack the gatehouse from wall-top level is a quick way to do this) the gate flips to neutral. Whichever party repairs the building enough to restore the gatehouse to functional state (so probably up to the Intact-Broken Gatehouse threshold) will gain control of the gate.

This state does not occur if it is built independently, where it behaves as a regular fortification until pounded into ruins (at about the same point as the gatehouse on top would have collapsed as part of a wall).

The Intact to Broken threshold should be around 75% HP, while Broken toe Neutralized occurs around 25% HP. So you have to repair for half the Gatehouse HP before you take it over (or it gets re-established as a defensive tower on your gate).
Gatehouses built alone as isolated fortifications simply get 25% less max HP.

Might require some sort of repair multiplier on these buildings as I’d rather an army of repeaters not be able to abuse 1 damage per arrow to down them too quickly. Or just not that much HP.

Filling the gate costs about 10 stone, and takes about 30 seconds. Balance so 4 Battering Rams, the most that can be reliably brought to bear on a 3x3 building as part of a wall, can approach and force a breach if the player is inattentive. Emptying the gate takes about 45-60 seconds and refunds 5 or more stone once completed. Has to be better value than a villager throwing up three Fortified Wall tiles behind the gatehouse (villager can be sniped).