AUTONOMOUS Half-Life 2: Episode 2
LEVEL OVERVIEW
Development InfoRole: Sole Developer
Genre: First-Person Shooter Game Mode: Single-Player Mission Engine: Source Development Time: 180 manhours |
Level Features
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High Concept
Defend a Combine teleporter against six increasingly difficult waves of zombies by utilizing three unique defensive summons.
Design Summary
“Autonomous” is a single player level for Half-Life 2: Episode 2 that takes place roughly between events of Episodes 1 and 2. In “Autonomous”, players assume the role of Combine Technician 343, the singular soldier sent in to reactivate an abandoned teleporter in Ravenholm. Unfortunately for 343, the unique energy signature emitted by the teleporter seems to attract every zombie in Ravenholm. Thus, as the teleporter charges up, players must defend it from six waves of zombies. If the teleporter takes too much damage, the player loses the game. However, as 343, players obtain the ability to summon three different types of Combine war machines: manhacks, turrets, and hunters. Players may place these summons wherever they deem fit in order to help them defend the teleporter from the zombies. Each summon costs a different amount of resources to build, and there is a finite amount of resources. So in order to achieve success, players must place their units wisely.
Design Goals
- Create a first-person tower defense level within the Half-Life 2 universe
- Give players the ability to summon three different defensive units (manhacks, turrets, and hunters) to help defend against the zombies
- Create a fully functional resource system for gathering supplies and building units
- Support multiple playstyles and strategies
Level Highlight: Defending the Tower...I mean...Teleporter
In “Autonomous”, players must defend a central point (a teleporter) from six waves of zombies. During each round, zombies spawn from four different locations across the map and path towards the teleporter to destroy it. The player loses the game if the teleporter takes too much damage.
Zombies Hate Inanimate Objects
In Half-Life 2, zombies by default attack the player without provocation. “Autonomous” utilizes creative use of AI relationships and navigation toward the teleporter to create a gametype where players could focus more on maintaining the defenses of a central point instead of constantly avoiding death from overly aggressive AI.
Here we see two misguided zombies getting shot in the back as a result of their teleporter obsession.
Creating Defensive Units
In order to defend the teleporter, players possess the ability to build three different units: manhacks, turrets, and hunters. A major design feature players experience in “Autonomous” is the ability to summon units wherever they want to. Granting this mobility and flexibility required creative uses of scripts and pre-existing console commands originally designed for debugging. This unique feature also allows for faster, more intense combat situations, since players are capable of summoning units on the fly.
In "Autonomous", the flying manhacks are the least expensive defensive unit to build. If players have a reasonable amount of resources, they can effectively spam these little creatures of havoc Though they deal very little damage, they excel at distracting and annoying approaching zombies. These guys can buy players valuable time in a pinch.
Placeable turrets are the second most expensive units to build. Turrets output a decent amount of damage, but their real virtue is that players can pick them up and move them to a new location at any time. This is extremely valuable when the attack front suddenly shifts. Additionally, turrets can not be killed, unlike the other two summons. That said, their biggest drawback is that zombies or headcrabs can knock them over quite easily, rendering them utterly useless until the player picks them back up.
Hunters are the final summon players can build. These aggressive units cost ten times more than manhacks, but are by far the most powerful. Hunters can take a tremendous amount of damage before they go down, and can effectively hold an entire corridor by themselves. If players save their resources, they should be able to afford one of these powerful units by the third wave.
Level Highlight: Supporting Multiple Strategies
Another crucial design goal of “Autonomous” was to allow players to play the game in multiple different ways. I wanted to avoid creating one particular dominant strategy that established itself as the only way to win. To achieve this, careful thought, planning, and tweaking went into not only choosing the three units the player can spawn, but how many of those units they can actually create at any given time. Thus, each of these units fulfills a different role and has different advantages and disadvantages as previously described.
The result of all this work allows players to create new strategies each time they play: one time they could build only manhacks and rely on their abilities at distraction to slow the zombies, while other times they could choose to save up for hunters and decimate the enemies with raw power.
The result of all this work allows players to create new strategies each time they play: one time they could build only manhacks and rely on their abilities at distraction to slow the zombies, while other times they could choose to save up for hunters and decimate the enemies with raw power.
Level Highlight: Building a Resource System
“Autonomous” features a fully functional resource system that keeps track of how many resources players gather from pods scattered around the map in order to determine if they have enough resources to build the particular unit they so desire. Half-Life 2’s editor features no efficient way of capturing and storing variables, so recording a constantly changing number such as a resource count and then accessing it whenever the player attempts to build a unit took a significant scripting effort. However, the result is that players can only summon units if they have enough resources and do not actually lose resources if they try and build something that is too expensive. The additional layer of unique resource costs for each defensive unit also adds to the complexity and depth of this system.