Today’s culprit intro sequence.

Hello and welcome to another installment of our series! It’s been a while since we presented the last part to you, but we’ve had a lot of work in the meantime. We attended Gamescom 2018, where we had the opportunity to meet some of you and we’ve been working on the recently announced Nintendo Switch port of X-Morph: Defense! We are back on track though, aiming to deliver articles on all of our boss designs. Let’s take a look at one of the most complex designs we had, the KM-2 REDWING ekranoplan.

A COLD WAR RELIC

KM2- REDWING model in-game. The screenshot comes from an early prototype, hence the shadow quality.

First, a little bit of history. An ekranoplan is a machine that’s something between a plane and a ship. It uses the ground effect to generate enough drag to lift off from the ground, or from the water surface, to be precise. Machines like these were supposed to revolutionize water cargo, by combining the speed of a plane with the capacity of huge container ships. Since research on ekranoplans was done mostly in the Soviet Union during the cold war, being undetectable by radar and immune to most navy weapons were additional advantages. The KM ekranoplan was a top secret project. Several iterations were made, more or less weaponized, but none reached the stage of mass production and the project was discontinued. 

The boss is able to drop multiple ground units to the battlefield. The cargo nature of its protoplasts shows.

In our version of reality, however, the research did not stop and the X-Morph attack pushed humans to deploy their newest gunship to the battlefield. The KM-2 REDWING ekranoplan is a spiritual successor to the earliest KM model, dubbed the ‘Caspian Sea Monster’. It is powered by multiple jet engines, which generate thrust and exhaust the air under the wings, generating the massive lift force required to carry this giant war machine. Equipped with lasers, rocket launchers, and anti-aircraft weapons it is the boss enemy of the Russia stage in X-Morph: Defense.

BOSS FIGHT DESIGN

Hitbox map of the boss. There were a lot of active parts at first. Later revisions reduced their numbers quite a bit.

Now that you have a general idea about the ekranoplan, let’s talk about what we wanted the fight to look like. The model is quite complicated, representing all the different systems the boss is equipped with. The player may choose what kind of approach they would like to take to fighting the boss - destroying the wings, engines or weapon systems are all viable strategies. We wanted all of those to lead to different outcomes, but more on that later. The fight itself would take place on a map that’s situated near a harbor. This decision was made both to emphasize the naval capabilities of the KM-2 and to give us possibilities of incorporating ground units into this fight.

The boss can fire multiple kinds of missiles at the core, each with a bit different characteristics. 

Even though all of the above is still true, a round of testing has shown an issue with our design. The number of hitboxes on the ship was much too high. This caused the fight to go on for a very long time if the player did not focus on dealing with the gunship. Since there were many distractions, such as the ground units dropped from the ekranoplan, or missiles fired at the core, the players felt threatened by too many things at once and often did not manage to get a decent hit on the boss. Thus, the number of hitboxes and distractors was severely reduced, leading to a more fun player experience overall.

The level design did not change much. Flight patterns have been reworked, other than that, we managed to stick to our early design.

Similarly to the bomber concept that we presented to you earlier, the boss would follow predefined flight patterns. At first quite far from the X-Morph harvester core, but getting closer as the fight progressed. In X-Morph: Defense we give the player perfect information about the wave they are about to face off against. It means we show all the possible attack paths, enemy numbers, spawn points etc. The first playable version of this boss fight, however, had so many possible paths that the ‘perfect information’ we wanted the players to have turned the screen into complete chaos. It was also around the time when we invited several people from outside the studio to help us test some ideas and all of them were confused upon seeing this. That is why we decided to limit the number of possible attack angles.

WEAPON SYSTEMS

Artillery barrage is one of the toughest attacks the boss has to offer. Without anti-air defenses, it is really difficult to counteract.

We decided to use a mixture of direct and indirect attacks against the core, each telegraphed to the player by a dialogue line. One of the marquee features of the KM-2 were powerful lasers, able to scorch everything in their path. The only means of defense against those was dealing enough damage to the laser cannons to temporarily disable them. 

A textbook definition of ‘scorched earth’ tactics.

The second type of direct attack were several types of projectiles fired directly at the core. The gunship would have a choice of using a swarm of small missiles, a couple of larger and tougher cruise rockets or artillery shells dealing splash damage. The small missiles are fairly fragile and the player can take them down in a number of ways, such as the EMP defense field. Bigger rockets can take a couple of hits or can be disabled by an EMP shockwave. The shells from an artillery barrage aren’t affected by EMP but can be shot down directly. Such a variety of attacks would require the players to have a decent network of anti-air defense towers or, thanks to the fixed flight patterns and clearly announced barrages, to counter those attacks directly with the X-Morph fighter. 

The player must find the balance between protecting the core both from the missiles and ground threats.

Not only the alien core was in danger while fighting against the REDWING KM-2. We gave the boss the ability to bomb the terrain, clearing the defense towers placed by the player and clearing other terrain obstacles. That last point was especially important, given the fact that the boss could drop ground units onto the battlefield. Apart from introducing another layer to the fight, this feature was connected to the cargo nature of the early concepts of real-world ekranoplans. The numbers of the dropped units weren’t spectacular, as we did not want to distract the players too much, just enough to keep them on their toes.

The boss is not defenseless if you try to backstab it. Air mines are quick and very effective.

The attack package wouldn’t be complete without actions aimed directly at the player ship, so we mounted miniguns, rocket launchers, and AA cannons onto the gunship. The problem with all of those was that they could fire in a limited radius, leaving the KM-2 defenseless if the players managed to position themselves directly behind the boss. The problem was essentially the same as in the case of the bomber, but given the lower flight altitude of the ekranoplan, we managed to find a solution this time. Taking deep-sea mines as an example, we equipped the REDWING with air mines. They would be dropped behind the boss, directly on its flight path, making sure the players weren’t able to easily exploit its vulnerabilities.

KILL IT WITH FIRE

It wouldn’t be an EXOR Studios game without explosions.

As for the kill conditions, we decided on three different ways the players could deal with this monstrosity. The first one was going after its engines. As the players dealt damage to engines, the boss’ behavior would become progressively more aggressive, as the crew would want to destroy the aliens before they completely lose all power. If the X-Morph survived the onslaught and managed to destroy most of the ekranoplan engines, the remaining ones would go into overload, leading to a spectacular series of explosions, concluding in an epic catastrophe.

A rudimentary schematic of the wing fragment hierarchy. The player must destroy the wing fragments in order.

The second way to get rid of the gunship was to destroy the wings. The players were able to destroy them piece by piece, lowering the lift force capabilities and eventually leading to the plane spiraling down and crashing into the ground. As in the previous example, the crew would anticipate this and become more pervasive in their attack patterns and barrage intensity. 

A well-timed EMP blast can damage multiple systems at once.

The last way the players could defeat the gunship was to destroy all of its weapons. All of the individual defense systems had their own hitboxes, making them targetable and destructible by the X-Morph. Once all of the KM-2’s guns were dealt with, the boss would switch into a kamikaze attack mode, going straight at the alien core in the last effort to stop the alien invasion. In order to make this preventable, the overall toughness of the ship would be lowered at this stage, giving the players the chance to destroy the ekranoplan before it hit the harvester core. In the end, due to time and resource constraints, we had to scratch the multiple endings idea. In the current version of the game, upon receiving serious damage to any set of components the REDWING first changes the attack pattern. Then, it attempts a direct core attack with lasers, similar to the kamikaze run, only to finally attempt it in its last stand.

IMPLEMENTATION PROBLEMS

This is NOT working as intended. We added an invulnerability shield to the core to prevent feel-bad moments.

A large number of targetable elements was also an attractive idea when the game was a pure shoot’em up. When we had transitioned to introduce the tower defense elements another problem arose - which part of the REDWING were the towers meant to shoot at? This problem required us to assign each individual part a targeting priority. First, they will shoot the elements with the highest risk factor or the closest one if all target priorities are equal. The only exception to this rule is the laser attack - when it is active, only the laser emitters are the targetable element.

The defensive towers switch between targets on the go, but according to a specific ruleset.

As we downscaled the complexity of the boss fight and the number of elements, the death sequence has been unified for all player approaches. The dialogues will acknowledge the damage done to the gunship, however, the fight phases are exactly the same. First, the boss tries attacking from a distance with long-range missiles. After that, it attempts to pressure the core by adding missile and artillery barrages to its repertoire. Lastly, it may attempt a suicide run at the alien base, unless it is defeated before it can go on a collision course. 

The player is able to defeat the boss even before it is capable of launching the final, kamikaze attack.

Of course, the plans we had in our heads at the beginning of the project were quite ambitious and due to time constraints and the game’s redesign we had to cut down on some things. This resulted in the version of the boss you encounter in the game today. The attacks remained largely unchanged. A large number of solutions were reused from our previous boss designs. 

CONCLUSION

The KM-2 model without textures. The perspective on this image makes it easier to spot the different weapon systems.

All in all, the REDWING KM-2 was not the most difficult boss to implement, technically speaking. We managed to reach most of the design goals we set for ourselves. The true challenge here was to show to the players how to fight this machine effectively and evoke positive feelings during the fight. After all, the challenges we set for our players are meant to be pleasant and gameplay is supposed to be fun. Without external testing, this would not have been possible, as it opened our eyes to many problems we previously did not think of. 

The cruise missile barrage is very dangerous, especially when launched close to the core.

Join us next time, as we continue on our journey through the 5 years of X-Morph: Defense development history. We will dig up a concept of a boss which did not make it past the design phase. Also, if you enjoyed reading this article and would like to ask us questions, leave comments here or join us on our live streams! We love hanging out and chatting with you!

Until the next time!
EXOR Studios

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