In Castles, the player must construct anywhere between 3 to 8 castles (depending on difficulty), with each castle comprising a single "mission" in the game. Starting with an empty field, you must design your castle using various set-pieces of walls and towers. Then, laborers of different professions must be recruited to construct the various stages of each piece. Taxes must be raised, and naturally an army built to protect the castle from attacks by various local factions (as well as some supernatural armies, when the game's "fantasy" mode is activated).
The game itself runs in Real Time. Occasionally, it is interrupted with cutscenes presenting a very short Dialogue Tree in which various characters appear at your court to request audience with you. Combat also runs in real time, with your hired defenders trying to prevent the enemy from toppling your built-up castle segments. Once the castle is complete (preferably with a moat dug around it), a massive battle erupts in which the locals make one final attempt to overwhelm you with great numbers. Successful defense at this stage will finish a "mission" and move on to the next castle.
The game was highly acclaimed, and received a reasonably good sequel that took the castle-building business one step further, mixing in "grand strategy" elements as your faction vied for control of Medieval France.
This work includes examples of the following tropes:
- Always Chaotic Evil: Celts, Picts. Then again, you are invading their land.
- Archenemy: King Charles of Bretagne is this to the original castle-building king.
- But Thou Must!: A messenger comes to you from Parliament, demanding that you change your taxation policy to adhere to the Magna Carta. Your options are to imprison him, ignore him, or say you'll do something but actually do nothing.
- Conservation of Ninjutsu: Sort of. The more soldier units you place on the map before a battle, the weaker each unit will be. That's because your total soldiers available will be split up into as many units as you've placed. Of course, having fewer units means it'll take longer to clear all enemy units, giving them more time to destroy your castle segments.
- Corrupt Church: In the sequel, one way to become king is by gaining the Pope's favor, and the main way to do this is by bribery (i.e. buying indulgences). Exactly what you'd expect for a game set in medieval France.
- Deliberate Values Dissonance: Quite a few of these moments exist in the game.
- You can respond to the King of Bretagne sending you tennis balls by declaring war on him.
- You can exile all Moneylenders (Jews) from Albion at the request of a Archbishop who just wanted you to tax them.
- You can burn down a Celtic village in response to rising banditry.
- Dialogue Tree: A special kind of tree that runs its course over several hours of gameplay, closely resembling how story events are handled in Crusader Kings and other Paradox Interactive strategy titles. Every once in a while the game goes into dialogue mode, showing someone visiting King Edward at court. A short narrative presents the situation, allowing the player to choose from one of a handful of responses. The game then briefly describes any immediate reaction or consequences, and returns to the main screen to continue building the castle. Some time later the game goes back into dialogue mode, with a new narrative showing how the player's previous choices caused the situation to develop in a certain direction. The player is once again given several reactions to choose from, et cetera. Though some of these mini-trees contain only one or two dialogue "sections" and effectively conclude as soon as the player makes a decision, most trees unfold gradually over the span of an entire mission - which can take hours.
- Expy: Exchange "Albion" for "England", "Gwynedd" for "Wales", "Pictland" for "Scotland", and on and on. Other than the names, everything else is pretty much the same. The manual acknowledges it outright.
- Golden Ending: You manage to conquer Wales, the Picts (Scotland), most of Northern Bretagne, and liberate Flanders. Your son can end up on the throne of Bretagne in the sequel as well.
- You manage to conquer all of France, establish trade with Africa, get yourself in with a rabble rouser, and also have the blessings of The Illuminati (no, seriously).
- Historical In-Joke: A lot of these exist in the original game, where you're basically Edward I.
- Homing Boulders: All projectiles. Also see No Arc In Archery, below.
- The Illuminati: The Brotherhood of the Eye is a potential friend in the second game.
- Immediate Self-Contradiction: In the Castles II scenario where the Queen proposes an alliance through marriage, she begins her speech by pointing out that you and she are both widowed. At the end of the speech, however, she says that accepting her offer will require you to put aside your current wife, Edna. Apparently you are widowed and married at the same time.
- Kingmaker Scenario: In Castles II, the Pope is the Kingmaker. However, you can Take a Third Option.
- Knight in Shining Armor: The entire family of the Westhampton Duchy. You can pretty much count on them to be loyal and trustworthy, and their advice should be heeded... in most cases.
- Medieval European Fantasy: What happens when you turn on "Fantasy" mode. Done very much in line with Briton/Celtic/Welsh folklore, and includes the Seelie Court, Ogres, black magic, etcetera. Church-figures who come to visit your court often seems befuddled and displaced as a result.
- No "Arc" in "Archery": None whatsoever. Arrows fly like bullets.
- One-Word Title
- Romancing the Widow: You can do this to King Charles's wife in Castles II, though she's much older than you and you have to put aside your own wife.
- Shoot the Messenger: When an opponent sends a diplomat to you in Castles II, one of the options is "Kill him."
- Siege Engines: Your worst nightmare. They seldom appear, usually only in the last battles of your last few castles in the campaign, on Hard difficulty. When they do, you'd better do your best to take them out pronto.
- Take a Third Option:
- You can conquer all of the Pope's lands in Bretagne and get the Antipope to declare you King of France rather than relying on the actual Pope's blessings.
- You can actually avoid a peasant uprising by just ignoring whenever a regular poacher flagrantly violates the law. Since he's an expy for Robin Hood. Eventually, he'll decide you're best friends and forget about uprising against you. He also gets murdered when he tries this on another nobleman.
- Video Game Cruelty Potential: You can exile all of the Moneylenders (i.e. Jews) from England, burn down a Celtic village, betray your allies, and numerous other terrible misdeeds. This aspect of the game was largely removed from the sequel.