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April 24, 2018

Gameplay Variety and Modularity

Gameplay Variety and Modularity

Let's look at gameplay variety. The number of possible gameplay scenarios a player can experience in Co-op is proportional to [#commanders] x [#commanders -1] x [#maps] x [#enemy races]; where "#" means the number of. Plus there are other less significant factors such as player and enemy unit compositions or map specific patterns which increase the number further. The cooperative nature and progression system help too, and the potential of mutations shouldn't be underestimated either.

This relatively high number of possible gameplay scenarios leads to a greater replayability than is usual for campaign missions. Those are often limited to one scenario per map with small variations provided by global upgrades and unlocks. However, even with this, Co-op can't measure to the competitive Versus mode, which has almost unlimited replayability through player contest and self-improvement.

Because of its non-competitive nature, having enough content is particularly important for a game mode like Co-op. In this post I will argue that having high modularity is a good way to provide more gameplay variety. However, it might not be the optimal thing to do in Co-op now. It would be easier to take advantage of tools that are already available. And by that I mean weekly mutations, which were abandoned for some time, and custom mutators, as there is little incentive to play them. The first step could be going back to making new weekly mutations, creating a lobby system for custom mutators, adding a matchmaking queue with random mutators or something completely different.


A system is modular when it can be subdivided into smaller parts "modules" that will work in a variety of configurations. Modules are connected in a standardized manner, and their main strength is that they can be easily changed and reused. While the term modular is usually found in connection to games in modular level design, it might be helpful to think of certain parts of a game as modules. Then we could look at gameplay variety as a number of all possible module combinations. Modularity might be reminiscent of systemic game design, but modules usually lack the level of awareness and interactivity systems have.

Co-op maps are already very modular. Commanders are created separately and are not restricted to certain maps. Enemy compositions and most of the functionality are shared between maps. Mutators are a great example of a module that affects all maps and commanders and yet functions almost independently. If I put Just Die! mutator on a newly released map and play it with a new commander, it will mostly likely just work.

It's generally better to build a system from the ground up with set modularity. Increasing it later takes a lot more time, and it's likely not a realistic change for Co-op now. However, it's interesting to try to learn from the current game, and see what could be improved. Let's look for places that would be suited for the modular approach and see what their hooks would be. I will use the term "hook" as a place or an event where modules communicate between each other or with the main system. Hooks have to be universal enough to fit all possible configurations. For example, many mutators come into effect when a unit is created, takes damage or dies.

Bonus Objectives

Bonus objectives are prime targets for becoming modular. They stand alone and do not significantly affect the difficulty of the main mission. Mixing them up would greatly increase the gameplay variety. They could be even completely replaced by other events.

To make them modular, all bonus objectives' data and triggers would be moved in the Allied Commanders mod which is shared between all maps. Each separate map would then call for bonus objectives through a function distributing them. This way, every map would have access to all bonus objectives and their assets. The advantage of this approach would be that a simple change to the distributing function could switch a bonus objective for another bonus objective or event. Also, new bonus objectives could be easily introduced into older maps.

Apart from randomizing and introducing new bonus objectives, there could be more interactions with mutators, and bonus objectives could be temporarily altered or replaced by special events such as in-game or cross-game promotions. Players could hunt pirate ships because of a new World of Warcraft or Hearthstone expansion, or they could collect parts from bonus objectives in a time-limited event, which would reward them with a new skin, mount or a companion in any Blizzard game. Daily or weekly quests could alter bonus objectives. Overall, modular bonus objectives would open a lot of options.

Problems with randomizing bonus objectives
  • Hooks have to be implemented carefully to ensure good compatibility. The most important part is choosing the best location. Even then, some bonus objectives, such as destroying trains, could only appear on some maps.
  • Voice lines for map specific announcers have to be flexible to accommodate for various bonus objectives. Optionally, there could be announcers just for bonus objectives.
  • Bonus objectives are often tightly integrated in a map so they fit the theme and gameflow. While it should be possible to maintain gameflow, not every bonus objective's theme is compatible with all maps.
  • Randomized bonus objectives have to be communicated early enough so players can adjust their gameplay (managing input randomness).

Even if these issues had proven to be too difficult to overcome or randomized bonus objectives didn't fit the game direction, having modular bonus objectives would still be an advantage.

Other hooks

Mutators are a special in that they have almost zero hooks in co-op maps themselves. Many mutators react to units, structures and resources, but that's automatic and map-independent. "Blizzard" mutator is one of few mutators that is affected by maps – namely the direction in which storms travel is different and hardcoded. Introducing more hooks in Co-op maps would make it possible to produce content that is more tightly woven into missions. The more hooks maps have, the more options there are.

Some possible hooks
  • Attack wave spawns. Currently, attack waves are called in several different ways. "Heroes from the Storm" mutator which is tied to them should "just work" on all maps, but unfortunately it doesn't.
  • Checkpoints marking players progress through the main mission (e.g., 25%, 50% and 75%).
  • Areas of main bases and expansions (useful for example for environmental mutators).
  • Areas of enemy bases.

Overall, this post is neither a critique nor a request for changes. Co-op has evolved spontaneously and is exploring relatively unknown sub-genre. It's interesting to learn what works, what doesn't and what could be improved. And while having modular bonus objectives would bring interesting options, it probably wouldn't be worth it now and development time would be better spent on something else.

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