THRESHOLD EXPERIMENT
Defense Against Invasion.
System & Technical Design Focused Project
Project Pitch.
Experience Goal:
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Create a tower defense experience for Fallout 4 players.
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Easy to learn, hard to master.
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Encourage strategizing for different enemy encounters.
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Encourage the player to determine the best solution to earn the most rewards.
According to the 2-month development schedule, I designed three types of turrets for the level. The machinegun turrets are for living creatures. The laser turrets are for robotic enemies. The cryo turrets are for slowing down the speed of all enemies.
Building a new system requires new ways to provide feedback on players' actions. I scripted this progression light to tell the player how many shots a turret needs to upgrade.
A basic of programming is preparing a factory function that executes all methods of different functionality. In this level, the factory is spawning a wave. The whole system starts to work whenever the player presses a button in the game.
According to the 2-month development schedule, I designed three types of turrets for the level. The machinegun turrets are for living creatures. The laser turrets are for robotic enemies. The cryo turrets are for slowing down the speed of all enemies.
Key Responsibilities:
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Documented and iterated level to shippable quality
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Designed and scripted the tower defense system, scripted special conveyances and feedback for the tower defense system
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Designed and balanced the level currency system
Project Information.
Threshold Experiment is a Fallout 4 mod level designed for tower defense gameplay. The level features utilizes 3 different types of turrets to fight against 10 waves of invasive enemies with a balanced Kill & Purchase system.
In this level, the solo survivor needs to assist a scientist from the Institute Advanced System in completing a test for their new turret system. Technical-wise, the level includes a fully polished tower system consisting of the following scripted functionality:
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​Activate turrets
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​Switch turrets
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Upgrade turrets
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Multiple wave spawners and escape points
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Invasion route conveyances
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Next invasion conveyances
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Ammo-based Reward & Purchase system
Engine: Creation Kit: Fallout 4
Mod for: Fallout 4
Work Time: Jun 4, 2023 - Jul 17, 2023
Team Size: Individual
Play Time: 30 - 45 minutes
Features:
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Fully Scripted Turret Defense System with clear conveyances and feedback
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10 waves of invasion with different routes
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Anytime to In & Out for the best reward
Feature Techniques.
Wave Spawner
Wave Spawner is implemented via a struct array that stores the ActorBase of the spawnee, when (wave index) to spawn, and where (spawn location) to spawn.
A public data set script storing all the independent variables is also used in the level for reference. Other scripts have their local copies of these variables when they are initialized.
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Whenever I want to change an independent variable, I can do so here, and all its references throughout other scripts will update automatically. This saved me a great deal of time in the later balancing work.
Whenever the player spawns a wave, if all conditions are met, the execution will first go into a "Factory Function" that triggers all other functions that relate to the functionality "Spawning a Wave".
Whenever an entity is spawned, it will register itself to a global list and global "On-Death Event, so that the system can trace its death. In addition, some enemies are scaled up by the system so that the player can easily see them in the arena.
Turret Interaction
To create a tower defense system, creative ways of handling I/O were designed so that the player is given three guns, Activator, Switcher, and Upgrader, to handle tower building, tower switching, and tower upgrading. The basic logics for these guns is similar:
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On-hit a target
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Apply functionality by scripted Magic Effect
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Inform updates of Feedback and Conveyance
Conveyances and Feedbacks
A new system requires new ways of Conveyance and Feedback. Several scripted conveyances regarding invasive routes, subsequent waves of enemies, turret type indicator, and enemies presenter are implemented.
#1 Dynamic.
Muti-Dimension Strategy Space
Three types of turrets
To prompt players to consider their turret choices for each wave, I designed and scripted three types of turrets: Machinegun, Laser, and Cryo. Each type of turret has its strengths and weaknesses.
Laser works better against robotic Synth
Their features:
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Machinegun Turret: do well in dealing with biotic enemies
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Unlock On-hit burning AOE on Level 3
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Laser Turret: do well in dealing with Non-biotic enemies one by one
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Unlock On-hit reducing energy resists on Level 3
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Cyro Turret: Deal no damage but is the best for slowing down enemies
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Unlock On-hit freezing nova on Level 3
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Dynamic Invasion Routes
Wave 1 - 4
To reduce the dominant strategy of surrounding the escape spot with a turret, I designed 10 waves of enemies invading from different spawn points and following different routes. This also challenges the player in terms of how to place different types of turrets.
#2 Clearness.
Turrets Conveyances and Feedbacks
Lights indicating the current level of the target turret
Challenge 1: Fallout 4 is a first-person shooter game that is incompatible with a tower defense system, especially regarding Conveyance and Feedback tools. To solve this issue, I designed and implemented several scripted conveyances and feedback mechanics for the turrets.
Routes and Waves Indicators
Invasion routes in the next wave
Challenge 2: Because of Fallout's limited visibility, the player cannot view the entire battlefield. So I designed and scripted the following conveyances to help with the system:
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Light up routes for each wave before the player starts the wave.
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Have "display cages" showing enemies in the current and the next waves.
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Let the player decide when to start a new wave, allowing them to spend more time observing the routes and building up strategy.
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#3 Balanced.
Balanced Enemies vs. Defensive Tower System
I put all the turret variants and the enemies together to make a matrix so that I was able to analyze the relationship among them. With these data, I retrieved the other two tables of dependent value, Dps (Damages per Second) and Spk (Seconds per Kill).
Later, because of this data outlined in the Level Design Document, I successfully crafted a first-pass, well-balanced level for further testing. As a result, in the later iterations leading up to the level launch date, my focus was primarily on addressing issues related to the low hit rate caused by the enemies' movement speed.
Postmortem.
What Went Well?
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Create a tower defense system in the Fallout world
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Successfully built a tower defense level using generic turrets and enemies.
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Have a good balance among invasive enemies, defensive turrets, and the kill & buy system.
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The system is robust and easy to reuse.
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Using structs and global variables to structuralize data​
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Public definitions are stored in a separate script, which provides an easy way to adjust and reuse.
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Conveyance and Feedback are good.
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Innovative use of a spawned route cat and display cage to convey the next wave's information.
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What Went
Wrong?
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Designed a tower defense level that is too classic.
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The player finds it hard to overlook the whole field because Fallout is a first/third-personal shooter.
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There is a dominant strategy in this level.
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The route design allows a dominant strategy where the player can only build the defense lines around the escape point.
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The cognitive Load is too high at the beginning,​ and the player has little things to do after figuring out the dominant strategy.
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Because of limited development time, the player needs to learn lots of things in a short period at the beginning of the level.​
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What I
Learned?
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Having an initial value matrix is helpful for later balance​
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I spent extra time setting up a basic matrix specifying how many enemies each wave and some dependent values, helping me analyze balance in the latter. development milestone
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Teaching a new system to the player required more levels or content than I expected.
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Recalling the tower defense game I played before, all of them use two or three levels to teach a single mechanics for the game before bringing in more depth.
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Gallery.
