Mirror matchups

Why do I find mirror matchups generally less interesting both as a player and a viewer? Is there something inherently more enjoyable about non-mirror matchups? I tried to pinpoint few reasons explaining this.

FIRST THINGS FIRST

1. Mirror matchups can be awesome too (see the linked game of Serral vs Rogue).
2. Balance doesn't equal fun. A perfectly balanced game can be boring, pain to play or extremely volatile. However, imbalances will hurt a good game.
3. Mirror matchups aren't affected by racial imbalances. Better players will usually win depending on the randomness of the game and the matchup.
4. If players choose vastly different strategies in a mirror matchup (e.g. bio vs mech in TvT, standard opening vs cannon rush in PvP, or roach-hydra vs muta-ling-bling in ZvZ). The game will behave more like a non-mirror matchup from the point when those strategies diverged.

Serral vs Rogue - game 4 (WCS Global Finals 2018) (32:35 – )

Potential reasons

1. From the viewer perspective, a game is more engaging if you are rooting for one side. If you don't have any preference for currently playing players, it's easier to root for one race or a distinct strategy. If both players are doing the same thing, it's harder to root for one side.
2. There might be some innate drive to compare different things, let them clash and see what comes atop. Seeing two knights fight is interesting, but seeing a fight between a knight and a samurai is even better.
3. When players use the same unit compositions or strategies, they will have the same strengths and weaknesses. This makes both strategic and tactical gameplay less interesting.
   • Armies favor similar arcs, and share the same preferences for open or narrow terrain
   • The same movement speed can make engagements more prone to snowballing
   • Both players are trying to do roughly the same thing. When one player gets ahead, neither player can take advantage of their distinct race mechanics (adds volatility).
   • Power-spikes will mirror each other (more about this later) (adds more volatility).

     (Note: I'm speaking about general trends. Mirror matchups can be very interesting both tactically and strategically if they are well-designed and balanced.)

4. Perhaps some volatility of mirror matchups stems from less clearly defined defender-aggressor roles (described in TerranCraft article). Players have to rely more on scouting, and it can be tricky even later in the game. This adds volatility to the matchup, and is harder to follow for viewers. In non-mirror games players will still often misjudge their current role, but those roles are more fixed in different game phases and easier to navigate.
   
   A rather special case were mass Mutalisk engagements that used to be almost impossible to predict when even few more Mutalisks could snowball the fight.

Destiny's special tactics with a Mutalisk cloud (19:50 – )

1. The number of combinations of viable strategies and openings will be usually lower for mirror matchups due to symmetry.
   
   Mirror matchups might also have fewer viable openings and strategies for each player. However, I don't think this has a significant impact. This number will vary a lot based on the current metagame, and StarCraft II is very focused on execution. Having fewer more enjoyable options is generally better than more options that are not as fun.
   
   Having fewer viable openings and strategies might be an inherent property of mirror matchups or a side-effect of balancing primarily for non-mirror matchups. Balancing three races is extremely difficult, and mirror matchups will always take a back seat. Balance changes can't affect the balance of mirror matchups, but there might be more concessions in order to balance non-mirror matchups.

game phases

With non-mirror strategies players will have different strengths in different parts of the game – game phases. This leads to more clearly defined defender-aggressor roles and a better story for viewers.

For example when a Zerg player gets Brood Lords, it's a clear power spike that changes how both players are going to approach the game (→ new game phase). A similar event is when a Protoss player is transitioning from a defensive role into an all-in. Even some upgrades can significantly change how the game plays as presented in the GDC talk by Dustin Browder.

(Note: It's an interesting talk especially when looking almost eight years back.)

Game phases (~18:28 in the GDC talk)

If both players are doing a mirror build, their timings will be very close. In high-level tournaments like GSL, production tabs can look almost identical for a long time. This will result in less game phases since power-spikes and other events will happen at around the same time.

Production tab seven minutes into the game (Maru vs Gumiho)

Furthermore, the fact that these events will likely not exactly coincide adds even more volatility to mirror matchups. Even slightly faster Zergling's speed, Stalker's Blink or Marine's Stimpack can shift the game in one player's favor.

StarCraft II's Game Design: How to Build an eSport (GDC 2011, Dustin Browder)

Wrap up

I think there are some good arguments why non-mirror matchups are more enjoyable. Most RTS games transitioned from early times—when there was just one race re-skinned several times—into more asymmetric designs. Starcraft led the charge in 1998 with 3 heavily asymmetric races. This significantly increased gameplay diversity spread out between 3 mirror and 3 non-mirror matchups, and brought other benefits to the game.

What are your thoughts? Do you prefer mirrors on non-mirrors? Any special reason why?