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Infiltration of the Submarine Base

A Third-Person Stealth Action Experience


The goal was to create a level where the player arrives at an abandoned/powered down base where through exploration, they are led to a mechanism that powers the base back up. Once this happens, enemies will spawn in and the player then has to reclaim the base through a combat encounter.

Basically, I needed to design a level containing areas that worked both for exploration and combat.


Created in 9 weeks half-time

What I did:

  • Level Design

  • Combat Design

  • Certain Whitebox Meshes

  • Level Scripting

Software used:


Getting Started

I had a rough idea of creating a facility of some sort near the sea. The player would start on a low point outside and make their way up inside the upper floor. The player would then reach the lower floor, a huge room underground where the main combat encounter would take place.

Gathering References

When it came to creating the environment and architectural style, I took inspiration from photos of factories and train stations from the late 1800’s to the early 1900’s. I also looked at various pieces of dieselpunk and steampunk artwork.

I started by jumping into the engine to quickly visualize my idea in 3D

I wanted to get a sense of space from the player's perspective early.

Blockout to Whitebox

Early blockouts and old layouts before redesigns

Final whitebox

Layouts and redesigns

All of the areas went through numerous changes in terms of layout, the most significant of which happened around the two interior combat spaces.

Through feedback from playtesting I found that the early versions of the lower floor were too cluttered and offered too many detours. I tried to fix this by narrowing down the playable area, trying to lead the player to the midst of the action instead of leading them to dark side alleys.

The initial upper floor layout was rushed and worked poorly as a combat space. I ended up deleting everything in the room and starting freshDesigning this room was challenging since you would play through the area twice; first as an exploration area where the objective is the maintenance elevator, and then as combat space with the submarine boarding platform as objective.

The upper floor, before and after redesign and iteration.


An intensity curve that roughly shows the level's intensity over time across the three acts.

Three Acts

The experience is split up into three acts. It starts off slow and builds suspense in the first act, before rapidly increasing in suspense as the second act plays out. The third act starts with some breathing room before increasing the suspense once again, and then decreases again before the level ends.

Cover to Cover 

When designing the combat spaces, I focused heavily on making sure the player always had access to cover. I set cover metrics to make sure that all low covers covered the player when crouching and all high covers covered the player when standing. I assigned a light brown colour to all low covers and a dark brown colour to all high covers for readability.

Enemy Movement

In order to manage the level difficulty and the enemy AI behavior, I divided their navmesh into zones in order to limit their movement. Some of them walk along a spline path, but most of them walk around randomly within their zone.

Rising Water Level

I had the idea early on to make the lower floor slowly flood as the player enters. I wanted to add a bit of time pressure, as the player would not be able to stay in one place for too long. But also to change the prerequisites of the level as certain areas become unreachable as time passes. Definitely the most experimental feature of the level.

Multiple Playstyles

Allowing the player to use different playstyles and take different paths was important to me. It’s possible to take a direct approach and run in guns blazing but it’s also possible to take the more stealthy routes. As such, the combat areas offer a variety of alternate paths the player may take as well as a few different weapon options if the player chooses to explore. I wanted to reward players who discover alternate paths. 

An example is when the player returns to the upper floor. Having killed the guard, the player is given three choices of how to proceed, each choice offers a different playstyle. A cautious player may take the side door since they are already familiar with that path. A bold player may open the big main door. It’s not very discreet but it makes for a cool moment. A stealthy player could enter through the broken window and take the enemies by surprise from the high ground.


First thing the player sees.

Story Premise

I imagine that this takes place in a dieselpunk world in the midst of a war between two factions. You play as a lone agent, tasked with infiltrating an enemy submarine base and stealing a submarine. As you arrive you find the base deserted with the bodies of researchers scattered about. The base’s robotic guards have gone rogue, killing anything in their path. The researchers managed to shut the base down before abandoning it. In the process of stealing the submarine, you accidentally reactivate the robot guards and are forced to engage them in combat in order to escape with the sub and complete your mission.

Act 1
Arrival and Discovery

The level starts with the player standing aboard a wooden boat overlooking the facility exterior. Having swam ashore, the player enters the facility premises. They quickly discover the bodies of workers who seem to have been thrown from the platform above. The player is led to the platform where more bodies are discovered after turning around a corner.


The area is damaged from a battle. Among the bodies the player finds a destroyed red robot guard. Foreshadowing of what’s to come.

The Upper Floor

As the power is out to the big door, the player enters the upper floor via a service door to the side. Upon entering they find a seemingly abandoned factory floor.


The large room is filled with red robotic guards that seem to be offline for the moment. As it’s quiet, the player will quickly reach a maintenance elevator at the end of the room. They also get some time to familiarize themselves with its layout. It will be useful later.

Act 2

The elevator takes the player down to a dark control room on the lower floor. Through a large window in the dark, the yellow submarine can be seen along with the rest of the floor. There’s a switch on the control panel and upon activation the lights come back on and the whole facility seems to power back up. With this, the robotic guards also come back online. The sequence ends with a level transition. 

The Lower Floor

Exiting the room to the left, the player reaches a balcony overlooking the entire lower floor. It’s a huge space filled with pipes, machinery and guards. The submarine is clearly seen down in the middle. The player needs to raise the submarine in order to be able to board it from the floor above. This is done from the second control room that is located up on the opposite end of the room and this is where the player needs to go next.


As part of the boarding procedure, water slowly starts to flood the room, so time is of the essence. There are two ways to proceed. The player can either descend the stairs and tackle the level head on, or they can jump to a platform to the left to try and remain on higher ground. Either way the player needs to traverse the lower floor, avoid or kill the guards and reach the second control room.

Combat Encounter

The robot guards come to life along with the rest of the facility. They are all armed with automatic rifles and will shoot on sight. The player stands little chance against them head on, making the best way to tackle them to either utilize covers or to do stealth kills.


The room offers a variety of different paths, some are riskier than others but they ultimately lead to two possible exit points. The one on the right is clearly visible but takes some time to traverse. The one on the left is a bit trickier to find but offers much quicker passage up to the control room.

Raise the Submarine

Upon reaching the second control room the player activates another switch that raises the submarine to the boarding platform stairs above. When the animation finishes, a level transition is initiated, which marks the end of act 2. The player now needs to return to the upper floor and board the submarine.

Act 3
Retracing Steps

Having exited the control room through a maintenance door, the player is now back at the battle damaged corridor outside. By retracing their steps the player finds that the stairs to the upper floor have collapsed.


By clearing some rubble, they find an alternate path which leads to some rooftops. Before jumping to the rooftops, the player can pick up a better assault rifle behind some rubble. After some platforming on the roof the player reaches the upper floor exterior. A robot guard is standing by the maintenance door with its back turned, an indication of what awaits inside.

Three approaches

The guard outside is a hint that things will be different once they get inside. The player is now presented with a choice of how to proceed.


The safest choice is to enter using the same side entrance as before, since it’s a route the player already is familiar with. Another route that is more risky is to go around the left corner and open the big main entrance door. It’s more spectacular but enemies will quickly be alerted to the player’s presence.


A more stealthy route is to go up the ramp to the left and climb up through the window. By taking this approach the player gets an advantage as they reach a high ground that allows them to plan their moves more carefully.

Upper Floor Revisited

For the second time the player enters the upper floor area. The main path is mostly the same as before, but this time the goal is to reach the boarding platform for the submarine. Guards are patrolling most of the room and the player needs to engage them in a second combat encounter. 


Gameplay may vary depending on how the player enters. If they enter via the big main door it won’t take long for the enemies to find them, as such the player is at a slight disadvantage when entering the area. If they enter via the broken window, they will find themselves at a covered high-ground with a good view of the first cluster of guards. Additionally, there is a sniper rifle which the player can use throughout the level, giving the player a major advantage.


Once again the player works their way forward by running and shooting from cover to cover. Upon reaching and activating the switch for the boarding platform, the player proceeds to the submarine and gets to look back at the level before descending the stairs and ending the level.


Full Playthrough

Closing Thoughts

This is definitely the biggest level I’ve ever done in terms of content and presenting it all in a somewhat compact way was challenging. While I am overall pleased with the results, I think downsizing and compressing the experience would have made it easier to both present and design.

Looking back, there are things I would like to change. For instance, the level does not look very much like an actual submarine base. Space planning in many cases could use some more work. It is definitely a case where believable space planning took a hit in order to make room for fun gameplay. The level is also filled with an open railing mesh that I added for aesthetic purposes. This became a problem later since they wouldn’t provide any cover in a combat scenario. I ended up having to replace the railings in critical gameplay areas. Lesson learned: open railings in a shooter level should be avoided.

Again, I am pleased with the results overall and I’m proud of what I managed to accomplish. I especially like that the entire experience can be played in full from start to finish

To end I've included a Google Drive link below where you can download and try it out if you're interested. I'd be glad to hear what you think!

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