As requested, here's an in-depth explanation of what caused the AI in Airships: Conquer the Skies to build outdated ships. I've tried my best to keep it relatively non-technical.

So in the game, the AI builds airships (and landships and buildings), and it researches technologies. Of course, it should use these new technologies in the construction of better ships. But a lot of the time, this was simply not happening, with the AI still deploying muskets and grenades late into the game.

After multiple tries, I finally figured out what was causing this bug, and also why it was so hard to diagnose.

First, some context: compared to other real-time strategy games, units in A:CtS are much more complicated. Instead of a single entity with one HP pool, an airship consists of dozens or hundreds of modules and tiles, all with their own stats. This is what makes the game fun, but it also causes performance problems.

This means that when the AI wants to build a ship, it's expensive to check every ship to see if it can be built. So instead, the AI keeps a list of ships that are buildable, and a list of techs it had when it made that list.

Whenever the AI wants to build a ship, it checks whether its list of ship techs is the same as the list of techs it's researched. If they're not the same, it's developed some new technology, so it re-checks all the ships and makes a new list of ships to build, and updates its list of ship techs with its current technologies.

So, step by step:


That last step is where the bug was: It should have made a copy of its current technology list and filed it away as the ship technology list. Instead, it just used the same list, the "live" one. So now, whenever it researched a new technology, it would be instantly in the ship tech list as well. Meaning that whenever it checked, the two lists would be the same, and so it would never notice technology had changed, and would never rebuild its ship list.


And so, the ship list stayed the same, with the same old ship designs, and the AI did not actually benefit from the research it was doing.

The fix was very simple: just make a copy of the tech list rather than use it directly. But what caused the bug in the first place? An optimization pass I did three years ago. These tech lists are used all over the place in the game, as they need to be consulted frequently to check if something is available. I discovered that the game spent a lot of time making pointless copies of them, and so I got rid of all that copying - including in this place, where there was a very good reason for it!

So why did this take so long to track down? You might have noticed that there were multiple previous updates where I claimed to have fixed this bug. Well, to be able to fix a bug, you have to first observe it in the wild. There's a bunch of confounding factors: perhaps the AI has outdated ships because it doesn't have the money to upgrade them, or they haven't made it to a shipyard because they've been too busy fighting.

And there's a lot of moving parts to ship management: I long thought the code for upgrading, rather than building new ships, was broken. So I asked players to send me saves of games where the AI had failed to build modern ships.

Here's the thing: the game doesn't store the ship list in the save file. It doesn't have to, because it can recreate the list, right? So when you loaded a save game with this bug, the bug would go away as the ship list would be freshly recreated and up to date. So I'd inspect the game and see correct ship lists, and hence assume the problem was with using the lists, not the lists themselves. The bug took so long to find because it was covering its tracks.

So here you have it: optimization always carries the risk of introducing new bugs, and sometimes bugs hide from you.

I think I've finally tracked down and fixed the long-running bug where the AI would fail to upgrade its ships or use new technologies it researched. Many thanks to everyone who sent in example saves. If there's interest, I can also write up an in-depth explanation of what small, stupid thing caused this bug.

• The AI now updates what ships it builds based on the technologies it has researched.
  
• The AI now correctly upgrades ships and buildings.
  
• Dead governors no longer stay at their assigned cities, gently decaying.
  
• Fixed a missing German translation.
  
• Flipped some defensive buildings that were facing the wrong way.
  
• Mod loading progress bar is no longer too short.

• Significant performance improvements to conquest mode: larger games should now run much more smoothly.
  
• Fixed a bug where the AI would fail to upgrade very outdated ships because even their upgrade was outdated. (Finally!)
  
• Off-road fleets with landships being stuck is now less likely, and is explained when it happens.
  
• Updated the Kingdom of Whalton AI fleet.
  
• Heroes and Villains: You can no longer use a spy action convince Bui to join your side if you're her nemesis, nor can you hire or convert Father Tesseract if you're a cultist.

Now Airships: Lost Flotilla is out I've finally been able to turn my attention to some long-standing bugs in Airships: Conquer the Skies:

• Made AI significantly better at managing money: it no longer builds and then instantly scraps supply ships, it does scrap useless city upgrades, it handles local defense budgets better, and it's more willing to fire overly expensive heroes. All in all, the AI should have a lot more money in mid to late game to compete with you.
  
• The AI no longer bothers you with boring requests to cancel treaties.
  
• You can now award medals to ships when heroes are set to none in setup.
  
• Half panels now flip with the ship.
  
• Fixed some missing text.
  
• When you capture an enemy ship under direct control, you don't then assume direct control of it.
  
• Cultists now start with only 30 reputation.
  
• Extra $10 local defense budget for capitals.

By the way, this is the last day where you can get Airships: Lost Flotilla for cheap through the bundle with Conquer the Skies.

https://store.steampowered.com/bundle/49670/Airships/

Celebrate the Release of Airships: Lost Flotilla with a Special Bundle! 🎉

I’m excited to share that Airships: Lost Flotilla is officially out now! To celebrate, I’ve put together a special bundle featuring both Airships: Conquer the Skies and Airships: Lost Flotilla.

https://store.steampowered.com/bundle/49670/Airships/

This bundle is a great way to explore both games set in the same universe:

In Conquer the Skies, you design and command your own fleet of airships in epic battles.
In Lost Flotilla, you control a single airship in an arcade-style autoshooter, battling waves of enemies, upgrading your ship, and charting your path to safety.
🎁 Bundle Deal: Save 10% on top of the 20% launch discount for Lost Flotilla!

If you already own Conquer the Skies, the bundle automatically adjusts its price so you only pay for the new game.

If you’d like to support the game, here’s how you can help:

• Write a review on Steam.
  
• Recommend Lost Flotilla to a friend.
  
• Share your favorite moments with me.
  
• Get the Airships: Lost Flotilla Supporter Bundle

I’m so happy to finally release Lost Flotilla and can’t wait to hear what you think.

Steam introduced a change to their launcher that broke the game on Linux. Version 1.2.7.4 fixes it again.

Airships: Conquer the Skies is part of the Planes, Trains, and Automobiles Fest which starts today. As part of this festival, the main game, the DLC and the soundtrack are discounted by 25%.

Also, I've made a small update for the demo of my second game Airships: Lost Flotilla. A torpedo boat! Check it out here:

https://store.steampowered.com/app/2978530/Airships_Lost_Flotilla_Demo/

The game now hides shortcut info when on Deck, in accordance with Valve's requirements for Deck compatibility. Also, if you are on Linux and the game incorrectly thinks it's on Deck, you can disable Deck support by adding the following line to vmArgs in config.json: "-Ddeck=false" (don't forget to add a comma after the previous line).

Oh look, another hotfix!

• Added missing buildings to an AI fleet.
  
• Updated Russian translation. (Thanks, Meowskyi!)
  
• Fixed clockwork zombie appearance.
  
• Fixed large dome decals.

Loading no longer hangs if you are not subscribed to any workshop items. Oops.