I’ve started working on a new computer game. I initially envisioned it as a cross between Dungeon Keeper 2 and FTL; you build a dungeon, gain monsters, and move them around your dungeon to respond to adventurers that try to invade. By surviving over several rounds, you gradually corrupt and take control of the land you are in, and a run involves corrupting several such lands.
In contrast to Icewords, for which development was very ad-hoc, I’ve decided to plan this game out in advance. I am making a game design document in as much detail as possible to have a clear picture of where I am going. I am also experimenting with test-driven development, using the Godot unit testing framework WAT.
Understanding the genre expectations of players is crucial when making a game. You don’t have to adhere to all of them, but it is easier for players to understand a game when they are already familiar with aspects of it. Dungeon Keeper 2 is the best example of the genre I am targeting. Some of its features that I see as essential are building a dungeon out of different types of rooms, attracting a variety of monsters to your dungeon, and using those monsters to fight off heroes that try to invade. Mining for gold while building tunnels is another iconic mechanic that would be good to replicate.
I decided to start my brainstorming with the concept of rooms. A large part of the progression that I envision in my game comes from unlocking, building, and upgrading many different types of rooms. Each room has a different effect and spawns a unique minion type. Some rooms can also transform when connected to others, an idea I got from Loop Hero. For example, placing a Library next to a Graveyard transforms it into a Haunted Library. Players like having little secrets to discover.
My initial vision for the rooms was as square tiles placed in a grid, like in Galaxy Trucker. When designing any spatial game about building something, I always ask: “Why does it matter where I place things?” In Galaxy Trucker, many threats come from a predictable direction and are more likely to occur in some rows or columns than others. While this makes sense in space, I didn’t see an obvious way to do something similar underground.
There are all sorts of ways you can make positioning matter based on the abilities of certain rooms. I object to relying exclusively on room abilities, however. It places a burden on new players; to make intelligent decisions about placement, they need to learn the nuances of each room. Therefore their heuristics are not transferable when exposed to new room types. I wanted to provide a reason to put a room in a particular location independent of what the room did.
I decided to try using tetrominoes instead of uniform square tiles. Most games that deal with tetrominoes ask questions about how efficiently they tile the board and what is on the spaces they cover-up. The latter focus is perfect for a game about building a dungeon because it is naturally suited to mining mechanics: you can print resources on the board for the player to harvest by covering them up.
Cover-up mining is probably enough to justify tetromino placement, but I wanted to make efficient tiling a focus too. In Dungeon Keeper 2, you gain a mana resource based on the area of your dungeon. In thinking about implementing a similar system, it occurred to me that rewarding the playing for dungeon area and penalizing them for dungeon perimeter naturally incentivizes efficient tiling. Mechanically, the player gains energy for each tile in their dungeon and loses it for each adjacent empty tile. Thematically, rooms generate mana and radiate it off into the environment. Mana thus obeys similar rules to real-world heat, which I like.
Such a system gives players two contradictory guiding reasons for tile placement. They want to spread out to harvest resources on the map, but they want to stay compact to minimize mana radiation loss. On top of this, they need to consider room evolution and any room abilities that care about proximity or adjacency. Overall, I think this gives enough reasons to care about where they place their rooms to make tile positioning meaningful.
At this point, I decided to try out unit testing in Godot while implementing classes to handle tetromino rooms and maps. I tried using GUT first but didn’t like that I couldn’t use arguments in my constructors with it, so I switched to WAT. I also prefer WAT’s integration with the editor over GUT’s requirement that you launch a scene to run your tests.
The biggest unexpected thing I learned is that unit testing is great for giving you feedback without having to implement example scenes. Previously, when making games in Godot, I would rush through a slapdash setup to get something I could play, leading to messy code that I would have to refactor. Psychologically, we want to see results for our work, and it is hard waiting for thousands of lines of code before you see anything happen – plus, you are almost sure to have an error somewhere. But being able to write a unit test and then immediately see results reduced this need a lot. Unit testing doesn’t just help you catch errors; it also helps you stay motivated.
Combat is the next consideration, which I am still debating. The planned structure of the game is that you cycle through the phases of building rooms, preparing for the heroes, and fighting the heroes. At first, I imagined this working like FTL boarding mechanics where monsters and heroes in the same room will automatically fight each other, and the challenge is allocating your monsters. Heroes would enter the dungeon from doors that lead out, so the layout would influence where threats appear. Battles would happen in real-time, perhaps pausing to cast spells or issue orders.
However, I’m not sure how interesting I can make that without becoming inaccessible. Crew combat is simple in FTL because you have to manage other things simultaneously, like weapons and power allocation. But if the focus is on fighting alone, I’m not sure it would be interesting enough to justify the phase. The issue with idle combat is that aside from the choice of where to allocate forces, the player has very little to do. Also, the idea of independent heroes invading from many different points feels off; capturing the traditional feel of a party venturing through a sequence of encounters would be better.
Another problem with real-time combat, in general, is that it severely limits the feedback you can give the player about differences between units. For instance, I recently played a newly released game called Hero’s Hour, where you recruit armies comprising many different types of units. However, combat involves a real-time battle where your entire army fights the enemy army, and it is difficult in the chaos to tell how each type of unit differs from the rest. I have observed this with RTS games as well; real-time combat smooths over the unique properties of each unit. I want the different monster types to have personalities, not blur together into generic minions. Therefore, I realized that I needed to have turn-based combat.
Currently, I am considering a system where a single party of adventurers encounters one room of your dungeon at a time, and you deploy monsters (and traps and spells) to that room as though you are playing cards. I was thinking about a turn-based idle system where heroes and monsters alternate dealing their damage, but that adds a lot of time to the game, and I’m not sure how your choices would change between combat rounds. If a spell is good to play, wouldn’t you spam it? And if you can’t, then why have multiple turns? Instead, my current vision is that there is one round of combat in which you play your cards and hit resolve, and then the heroes progress to the next room.
I’ve been playing a lot of Spirit Island lately, so it occurred to me that the power thresholds mechanic would work well with such a combat system. Each room and monster in the room provides elements, and each room, monster, trap, and spell has two effects – a weaker default effect and a better effect that applies when used in a room with the matching elements. I still need to figure out what makes the most sense thematically for how traps work.
I love reading or listening to post-mortems and designer diaries, but my games often have few records about why I made the choices I did or what issues I encountered. I think recording my reasoning as I go is valuable not just for looking back but also to help understand my design choices as I make them, so I will make more of an effort to post about it here.
