Gameplay
Background
Back in late 2016, DOOM absolutely blew me away with its incredible gunplay and frenetic action. Although the game would not feature mod support, id Software implemented a map/gamemode editor akin to Halo's forge mode as an apparent stopgap solution. Snap Map (as the editor was dubbed) boasted a suite of assets to mess around with and, more excitingly, a physicalized "coding" system that allowed players to build logical structures and call functions to create their own game mechanics. Eager to get my hands on the tool, I set out to create a fun project with it -- a Call of Duty Zombies style horde map replete with purchasable weapons, upgrades, secrets, and unique encounters. Enter, Horde Mode: Hell Station!
Map Layout
One aspect of Call of Duty Zombies that I really enjoy is that each map is essentially a puzzle that can be solved, where secrets and story elements are revealed to the player across multiple playthroughs. Backtracking is often utilized really well in these maps -- a switch on one side of the map might reveal secrets all the way back at the start. Hints are delivered through environmental storytelling, which adds to the play experience in both atmosphere and functionality. Backtracking is heavily utilized and, if done well, compels the player to make full use of the space and pay attention to every detail, allowing the designer to really push the interstices of the map without losing player attention. It's essentially a metroidvania-style approach to map design that I absolutely love in an endless mode like Zombies. This design paradigm also lends itself well to a mapping tool that is heavily asset constrained like Snap Map, since you can build a lot of content into a comparatively smaller space. As such, I wanted to make a map that adhered to these design principles and supported the idea of multiple engaging playthroughs.
The map itself is divided into two distinct areas. In true DOOM fashion, the player begins the game in the Hell area, and can unlock the ability to travel between the two areas by activating the teleporter.
The portal is located in the starting room along with a locked door that contains the double points upgrade. In this kind of level design, I like to situate mysterious "locked door" motifs right at the beginning to serve as hooks for player interest, encouraging them to seek out a solution while they play and return once they think they've found one.
The portal is essentially the primary objective of this part of the map, and is unlocked in two stages. First, the player must find the key and unlock the corresponding door. Second, the player flips the power switch and returns to the portal in order to use it. Since this is primary to the design of the map, the key is placed conspicuously along the most direct path to the door.
The rest of the map is saturated with various powerups and weapons that can be unlocked either through discovery (metroidvania shenanigans) or spending souls that players can earn by damaging or defeating enemies. I placed these points of interest to prompt player movement through the full length of the map, and to provide meaningful choice for players looking to strategize on repeat playthroughs.
For example, a player might be keen to unlock the double points upgrade as quickly as possible after discovering it on a previous playthrough. This will require them to rush through to the far end of the map, retrieve the key, and then return to the starting room to unlock the upgrade. They might discover in the key room that there is a powerful weapon available to purchase -- the Super Shotgun. This weapon is very difficult to afford without the Double Points upgrade, so the player will have to return to the key room again in order to acquire it. Alternatively, the player can work their way to the opposite end of the map to retrieve the Damage powerup, or simply take the portal the space station early to score some other powerful weapons in that location instead. The idea is to prevent the player from camping in a single location and to keep them in a constant state of decision making -- maintaining engagement and presenting discoverable objectives.
The station keys are used to unlock powerful weapons in the Space Station area. Players might return to the area to grab them after discovering their corresponding "doors" in the Space Station.
The station keys (power cores that slot into color-coded receptacles) are required to access the chainsaw and the BFG. The BFG receptacle is located inside the boss room, where the chainsaw receptacle is directly in front of the door. The Gauss Cannon is the weakest of the three super weapons and is therefore available to purchase repeatedly for a large amount of souls. The station also hosts a number of powerful upgrades and weapons for souls.
Snapmap Logic
A quick primer on SnapMap: In the editor, we can drop nodes into 3D space. These nodes represent functions and variables, and can be connected in order to interact with each other. We can use this system to create trees of functions that execute during run/load time.
One of the simplest trees I created for the map is the shop tree. The shop tree consists of 6 nodes, with a console acting as both a 7th node and an in-game object. When the player interacts with the console and selects the purchase option, it uses a "spend resource" function to attempt to subtract a number of souls from the player's collected souls. If the spend function is successful, a defined item is spawned on the location of the final node in the tree.
Of course, the trees you build can get quite a bit more complex than that. For example, here is the tree that controls the spawning logic during runtime:
This tree controls all of the spawning logic for the wave-based enemies and the corresponding UI elements that communicate some of this information to the player. The tree functions as a loop, fully executing with each round. At the start of each round, enemies are spawned in, and continue to spawn in waves as the player defeats them. When the round timer expires, the remaining enemies explode and the next round begins after a brief break period. Difficulty variables are incremented at the end of each round, and the small helper tree to the right uses these variables to modify the stats of enemies as they are spawned. A different tree handles player resource and scoring variables.
The upside of the SnapMap system is that the implementation is intuitive, visual, and fairly flexible in what you can do with it. An obvious downside is the fact that the organization of nodes can be pretty challenging, especially when many nodes need to link together...
The above is the tree that controls the room containing The Lost One, a custom boss fight I created. In order to implement the mechanics I wanted, I needed to connect a lot of nodes to the primary boss fight tree. Since there is no way to customize how these connections and nodes are rendered, it creates a bit of a visual mess. I was hoping to see more tools and features that assist with organizing and displaying nodes in DOOM Eternal's SnapMap, but alas, SnapMap was removed from the sequel and this is the way things are.
As for the fight itself, the Lost One spawns in when a player enters the room, putting a forcefield over the door and pausing the current wave. Ammo will spawn at regular intervals on top of a random platform. A ten second countdown will appear onscreen, indicating an incoming surge of demonic energy. At the end of the countdown, explosions of enemy will cover the floor of the arena, forcing the player to get to higher ground or risk taking extra damage. Meanwhile, the Lost One (a significantly stronger version of a revenant demon from the base game) will fly around the room firing off volleys of high-damage missiles at the players. Upon defeating the boss, the exit door is opened and the power core receptacle that unlocks the final weapon of the map becomes accessible.
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