The Kingdom games are a fascinating development in the genre of 4X (“eXplore, eXploit, eXtend, eXtinguish”) games.

For example, instead of taking place on a grid or plane, they happen on a line. They are also games of hard resource management, and in the case of the first one, of endurance gameplay.

Thomas "noio" van den Berg and Coatsink recently released a sequel, Kingdom Two Crowns, that plays with the formula in interesting ways, adding in multiple kingdoms to run, a second currency, and even a co-op mode. We talked with creator van den Berg about the game and some of its unique ideas. Also chiming in with his own opinions is creative director for Two Crowns, Gordon van Dyke.

Edited for length and clarity.

Why indies gravitate to "roguelike" design

The original Kingdom is billed as being inspired by roguelike modes of gameplay. We asked about how those ideas inspired the original game.

van den Berg: I'm not very well versed in classic game design vocabulary, but for me "roguelike" is a very natural consequence of a design methodology used by indies. It is an effective way to 'automatically' scale the difficulty of the game so that each run goes from "too easy" to "too difficult," and that there is thus always a part with interesting difficulty in between.

Additionally, for indies, it allows you to make effective use of assets because certain parts of the game will be repeated. One might even be able to avoid having complex savegame mechanics because the game restarts.

[F]or Kingdom, the rinse/repeat nature of the game is more of a consequence of how the game was designed, rather than a goal from the start. We discovered throughout Kingdom's lifetime that there is a great satisfaction that comes from building things up in a more permanent way, so Two Crowns reflects that.

van Dyke: I came into the project to help with design after the "roguelike" design was in place, and for me it felt like the natural choice for Kingdom. There was a puzzle element to it where you mastered it with strategic decisions over impulsive ones, no different than Tetris. And like Tetris, impulsive choices always caused your journey to end sooner than later. So, for me "roguelike" became an easy term to use when explaining the basic design loop to a broader audience.

Like Thomas mentions, we saw a lot of players forming a natural attachment to their Kingdom. And with Kingdom Two Crowns having a lot of big changes it was the perfect time to move towards an experience that was more about protecting what you built rather than only defeating, or escaping.

As a big fan of Infinity Blade, [that game's] descendants narrative was a means to soften the edge on roguelike design [and was] an inspiration for the decay design we adopted. This let players in Two Crowns keep a majority of what they built after inevitably losing their crown(s), and [was] a bigger motivation to continue playing.

Exploring a one-dimensional world

The maps in Kingdom are unique in that they each only go left and right and are one-dimensional.

van den Berg: I like the panoramic visual aspect of it, as well as the fact that it equates moving through the world with "panning" the map. Actual platforming movement (e.g. jumping) would get in the way of the strategy aspect, I think.

However, in terms of strategy, it can be hard to find gameplay mechanics that allow very complex tactics by the player. Units are either in-range or out-of-range on a one-dimensional line, there's not much more to gain from squad placement.

What is also interesting is that when units are placed on a one-dimensional line, you are forced to allow them to "overlap," which means that multiple units can be in the same place. That has some consequences for the design behind area-of-effect weapons (like the catapult boulder in kingdom). When you add hard defenses (walls) to that mix, it means that 20 enemies will pile up in the same spot and are all hit at the same time by a boulder. This makes some game mechanics much less predictable/controllable.

van Dyke: My background before Kingdom was designing in 3D worlds, and a majority of that was on Battlefield. So, for me it was an amazing challenge and that is my favorite aspect of sticking to the one-dimensional design. It forces you to be much more creative in the design and lends to solutions that keep in line with the core of Kingdom very nicely. This also means I don’t dislike anything about it.

Moving beyond Civilization

van den Berg: I think to make "another Civilization," you really have to want to make another Civ. Those games are very well thought/planned out, and my guess is that their development process is not super experimental.

Kingdom started off with the king on the horse, riding through a world. Then I started adding elements to this world that would be interesting to find/fight. The enemies were a relatively late addition to the original Flash game.

"1:1" design

Kingdom and Two Crowns both use a very interesting visual metaphor for your money: it’s represented as a little money pouch in the corner of the screen. Income goes into the pouch as physically-active coins; debits disappear from the pouch individually; if the pouch fills to the top, coins spill out and lands in the water, lost. The sequel expands this by adding a second kind of currency, gems, that goes into the same pouch.

van den Berg: The money pouch is a result of a "1:1" design methodology. Everything in the world is represented by an entity, there are very little "aggregate numbers." As such, each coin is one coin in the bag, and not a number on your screen.

The maximum number of coins is quite generous, so it never limited us. Now that we're expanding the tech tree (upwards) things tend to get more expensive, so the size of the bag might be more of an issue, but it's OK so far.

I've always resisted having an additional separate currency, so adding the gems into the bag was an idea by Gordon and Coatsink to mix in a currency without introducing complication. I think there are some "gotchas" around this combination (you cannot drop gems until the bag is empty of coins first), but then again, those are also fun things to learn to deal with.

Kingdom's intricate and expressive pixel art

van den Berg: I used pixel art because it is fun to learn and make, and it is economical. Especially when I was working on Kingdom alone, I needed an art style that has the shortest possible path between sketch/production/in-engine.

I suppose I was influenced by some retro graphics, but I like pixel art most for the "impressionist" feel that it gives. The viewer fills in the details with their imagination. I do not think it introduces many challenges compared to other visual styles. Some issues that everybody will run into are aliasing that results from rotating pixel art. Finding a font and UI design of the right size also took some work, because pixel art does not let itself be scaled to arbitrary sizes (without losing consistency).

van Dyke: Personally I never worry about someone who would look down on pixel art, or look down on anything or anyone. They aren’t the kind of player we’re looking for anyway. For example, when Two Crowns began we never once considered moving away from pixel art. For us it is part of the DNA.