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  • Postmortem: Skirmish Line

    - Tony Hua

  • Design

    The 33 Rule

    Borrowing Firaxis' 33 Rule, the goal with Skirmish Line was to make a game with the basis of Mud and Blood 2 while changing and adding enough to the game to create a new experience. In essence, a third of the game would remain the same, a third would be changed, and a final third would incorporate new mechanics.

    The Good

    Being a first project, being able to build the foundations of the game after an existing game was a big help. The original prototype of the game was simply an attempt to copy all of the mechanics of Mud and Blood 2. For a beginner, this cuts out a lot of unknowns and gives a core goal for everyone to work towards.

    By working with a game in mind, we can also make conscious decisions to change elements that didn't work well. For Skirmish Line, we abandon the "6 man rule" from Mud and Blood 2, a behind the scene rule (known only by the most hardcore fans of the game) that would induce artillery strikes on the player should their number of non-hidden units exceed 6 on the field. This change radically alters how the game would play out, but we found this made the game more accessible for players.

    The Bad

    Sticking to the rule means refusing a lot of changes. For Skirmish Line, this means keeping things like single unit selection, the top down view, and also things like the general inaccuracy of weapons, which we felt were a core part of the game's systems. We received a fair amount of negative feedback for this, with some players claiming the game is a clone of the original game with no improvements but also quite a lot of players praising the changes and new additions. Ultimately, sticking to the 33 Rule means some players are going to think the game isn't different enough.

    The Unexpected

    In the attempt to copy the core mechanics of the game during the prototyping phase, the mechanics actually turned out to be different in nuanced ways. Since we don't have access to the source code of Mud and Blood 2, our own interpretations of mechanics often resulted in very slight differences that would have notable gameplay effects.

    In removing certain mechanics, as the aforementioned 6 man rule, we found new problems. The 6 man rule acted as a cap/limiter on the number of units for the player and helped prevent the player from hitting a critical mass of units To solve this issue, we had to get creative, first implementing an alternative, soft version of the 6 man rule in which the enemy boss wave spawn chance are increased as the players have more units on field. When this wasn't enough, we implemented new ways for enemy units to tackle the players' defenses. We added a smoke screen that would deploy in front of a boss wave. Certain enemy units would throw smoke grenades to conceal the movement of fresh enemy spawns. Special waves that adjust accordingly based on the number of units the player has on field.

    It took several months of playtesting and experimentation to fix the gap in the design left open by the removal of one mechanic. When we simply tried to implement the 6 man rule itself and variations of, players felt frustrated by the seeming randomness of artillery strikes. Our eventual solution resulted in a variety of new systems that would further distinguish Skirmish Line from Mud and Blood 2.

    In-Game Achievement System

    A hallmark of the Mud and Blood series itself is the presence of an in-game achievement system called Medals and Ribbons, which require the player to accomplish certain feats in order to unlock various bonuses.

    The Good

    An in-game achievement system helps add a lot of replayability. While many players already naturally attempt to experiment and try new playstyles, an in-game achievement system can help push the players towards new areas that they might normally miss or simply add new challenges for the player. All in all, this is a fairly low cost mechanism for replayability and can really help extend playtime.

    The Bad

    The biggest cost of in-game achievement goals is that it is often difficult to design interesting challenges. For starters, goals have to be challenging enough to be meaningful but also feasible enough for players to achieve. When you take into account varying player skills, an achievement system may discourage players. A mixture of easy and hard challenges is an important consideration for player retention.

    The Unexpected

    Another major decision was to reduce on the number of grindy medals and ribbons. For an example, Mud and Blood 2 had a medal that would require the player to bypass 10000 waves within their first 99 games, requiring the player to average over 100 waves a game. This is further compounded by the requirement that this be achieved within the first 99 games on a player's profile. Players would have to restart their profile if they failed the requirements.

    The decision was made to cut the number of games on similar medals in Skirmish Line and to have the requirement be based on a rolling score of the player's last set of games. While many players appreciated this change, a few diehard fans actually want those grindy achievements, perhaps conflating grind with difficulty and challenge. Nonetheless, we made a conscious decision to not push our players into what seem to be an arbitrary skinner box.

    Mutator Systems

    Skirmish Line incorporated a mutator system we called "challenges", not to be confused with the in-game achievement system. The challenge system is a set of mutators that modify existing rules within the game. For instance, the "Just a Flesh Wound" challenge would reduce the healing rate to 10% of its normal value while providing the player with 2 additional points of resources each wave.

    The Good

    A mutator system was another very effective and low cost feature. Requiring no new art assets or much in the way of programming, the system added new ways for players to enjoy the game. For what was a very minor system, a lot of players praised the feature, citing it as an interesting addition to the game.

    The Bad

    Mutator systems run the risk of confining the game space. One of the challenges, "Jack in the Box" became very popular with players. At some point, the mechanism behind this challenge actually came in conflict with a later planned system. Since the challenge was popular with players, we couldn't just remove it. We had to modify the planned system instead.

    The Unexpected

    For what would be a well liked feature, the challenge system was a random idea that I felt like incorporating on a random whim. From there, I began to take the mindset of actively looking for low hanging fruits that can be implemented.

    Campaign Mode

    Skirmish Line has an extra feature where players can purchase units beforehand and go on the offensive. Units would be persistent across missions, which themselves can be completed unlike the endless defense missions of the core game. On paper, this all sounds pretty cool.

    The Good

    Campaign Mode was initially coded in 2 days after having watched a series of tutorial on serialization (how to save your game). Campaign Mode is also an extra feature that could be used to help market Skirmish Line.

    The Bad

    Building a feature in 2 days on a whim and expecting it to just work is a bad idea. Building a feature in 2 days because you are feeling pressured to make the game work on mobile devices because the core structure of your base game modes don't allow for easy serialization is an even worse idea. Campaign Mode was a feature that was outside of the scope of the project, and the biggest example of a feature that needed to be cut from the game early on.

    At the time, I was under pressure to find a way to make the game mobile compatible. Since much of the game's systems were built using coroutines, it was very difficult to serialize the game. This wasn't a major problem on PC since games weren't expected to take longer than 2 hours, with most being under 1 hour realistically, but mobile gamers would expect to be able to play in very brief intervals, thus necessitating either shorter missions or an ability to save the game's progress.

    I did a lot of tweaking of Campaign Mode, but it never was quite as fun as the two endless defense modes. Ultimately, it was a feature that probably should have just been dropped, and the development time on it spent elsewhere.

    The Unexpected

    Steam actually cares about what you put on your store page, at least when it comes to potential false advertising. When we submitted the game for review, we had advertised 3 game modes. One of these game modes was Campaign Mode, which we had disabled on the menu at the time being because we wanted our players' attention to be focused on the two endless defense modes for the launch period. Subsequently, we had to re-enabled Campaign Mode in order to pass Steam's review check before the game could be released on Steam Early Access.

    Distinction Mechanics

    One of the most important thing when it comes to your designing your game is to consider how to make your game distinct. A general rule of thumb that I have gathered is that there are two primary ways to make your game stand out: 1) Make your game the most polished of its kind and 2) Make your game different enough that nothing else quite matches it. As an indie developer, I can't match the graphical fidelity of most other RTS games. So for Skirmish Line, this means abandoning a lot of what would be considered normal for a RTS game in order to embrace something different.

    1) No group unit selection

    A popular feature of virtually every RTS game is the ability to select and move multiple units at once. For Skirmish Line, we stuck with the single unit selection as from Mud and Blood 2 because we wanted to simulate the difficulty of managing a large squad of soldiers. In addition, this helped attached players to their units, as each soldier had their own individual name and backstory.

    2) Visual Obstructions

    In most RTS games, a variety of UI elements allow players to easily identify and locate their units. With Skirmish Line, individual units can be buried underneath other graphical assets. For instance, smoke grenades can make it harder to spot units by concealing them under a smoke cloud, similar to how smoke work in FPS games. Large clusters of units together would make it harder for players to identify specific soldiers. Even trees can hide units underneath.

    We also implemented a "Roll Call" function in the game which prompts a UI indicator above all of the player's units in-game detailing a rough estimate of the unit's health status. If players want to get a more accurate status reading, they have to click on a specific unit. Roll Call gives the bare minimum for players to make a quick battlefield assessment, and the player must make a conscious decision to order a Roll Call. This helps build the mentality of squad management and adds to the overall theme of hidden information.

    3) Hidden Information

    In most RTS games, the health of both friendly and hostile units are clearly visible. Even upgrades or items are usually visible. By comparison, Skirmish Line offers only limited information for the players. Whereas players can inspect their own units individually for their full status, enemy units have virtually no information revealed to the player. This helps prevent players from being able to pick one the weakest targets, as common in many RTS games. Instead, players can attempt to do so by estimating the remaining health on enemy units through observation.

    4) Indirect Unit Control

    Soldiers also pick their own targets. All soldiers follow a rule based targeting system but some randomization is thrown to make target selection imperfect. For instance, most soldiers in Skirmish Line are programed to target the enemy within the closest distance, but we add/subtract some random value from the distance so that soldiers will sometimes pick a target that's slightly further rather than the immediate closest.

    With this mechanic in play, we implemented direct squad orders. The most notable is the "Concentrate Fire" order, which allows the player to order every soldier to target a specific enemy unit. This grants the player direct control for a quick second, but the player must use the order judiciously with respect to the order's cooldown. On a more abstract level, sometimes it may be better for the player to simply let their units pick their own targets, in order to maximize a spread of fire on enemy units.

    This is an important distinction as soldiers in Skirmish Line feature a "suppressed" state. Suppressed soldiers do not move and do not fire back. When a Concentrate Fire order is given, all of the players' units will fire on a single target, thereby allowing the remaining enemy soldiers to freely fire back on the fire.

    The combination of soldiers picking their own target and suppression mechanic further builds on the squad management mentality of the game.

    5) Whacky Stuff

    Skirmish Line is built with black humor in mind. Despite the truthfully horrifying nature of war, the game's general aesthetics, from the art to the writing, has varying degrees of humor. The flamethrower unit is described as a mobile barbecue unit. Bodies explode into giblets that spin in the air all over the screen with various organs visually intact. Crates burst open with umbrellas, rubber duckies, and other nonsensical items that wouldn't fit in a warzone. There are holiday events with turkeys, the Easter Bunny, and Santa Claus.

    6) Unfair, Random, Brutality

    The last element of the game is that it's brutal and sometimes even seemingly unfair. Skirmish Line has large degrees of randomization. This helps keep the game fresh, sometimes giving players a brutal game and sometimes giving them an easier run. Reaching a high wave score is only one metric for success. Instead, the game encourages the player to succeed across multiple runs, with in-game achievements that are earned by consistent performance.


    These are all conscious design decisions that give the game its own distinct identity that separates it from other RTS games. Some players object to these decisions, with some players wanting perfect information, some desiring greater control over their units, some finding the game too difficult, and even some wanting the game to be more serious and less whacky. But most players tend to find these elements amusing, fun, and unique. Perhaps even more importantly, this satisfied my own creative vision.


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