The initial idea was to create a survival horror co-op experience set aboard an abandoned spaceship, where players must share each other's light sources to survive illusions caused by anomalies.

I used Unreal Engine 5 and the First Person Shooter Template Pack (FPSTP). Being a dad, I could only spare about 5 hours a day over the weekend for the game jam, totaling around 10–15 hours. It went horribly, as I spent most of my time debugging replication blueprints.

Looking back, the prototype was clearly overscoped given my speed (or lack thereof) in writing replication code. Here's what I initially planned:

• A generator emitting light to maintain both players' sanity, which could be picked up and dropped.

• Each player equipped with a headlamp providing a cone of light to resist sanity loss.

• An enemy that spawns from an alien sac when touched or shot, featuring basic AI.

• A spawn manager to handle random distribution of ammo, alien sacs, and fuel barrels.

• Sanity-draining volumes assigned to dark zones.

• An engine room that accepts fuel to trigger the end-game condition and update the UI panel in the pilot room.

• A basic circular layout containing around six rooms (excluding tunnels).

• Sanity-dropping screen effects.

• Alien sacs or enemies spawning based on player sanity.

All of this needed to be fully replicated. Debugging replication was extremely slow, and testing the core loop was painful — it was tricky to control two windows at once just to keep the headlight trained on the other player.

While most features were technically implemented, some didn't replicate correctly, breaking the gameplay loop by the end of the 72 hours. I soon decided to return to the drawing board and move the game to the Extra category.

This time, I chose to start small, focusing on a simple but immersive single-player experience. After playing a few other jam entries in the Jam category, I decided to pivot to a lonely space scavenger concept—salvaging junk in the hope of bringing something valuable back to the ship.

The new, smaller scope included:

• A gravity gun to attract and launch space junk.

• A gravity-switching room to separate two drastically different experiences: flying in space and walking inside the ship.

• Doors that could be locked and unlocked at runtime.

• A few junk foods (no pun intended), like fries, which could be interacted with using the gravity gun.

I spent a fair amount of time ensuring that the atmosphere—especially during gravity transitions—felt right and immersive. This even involved some early SFX work, which I felt was essential to establish the game's tone and help me move forward with confidence.

After that, I allowed myself to "noodle"—experimenting without a concrete plan, guided only by the immersive experience I wanted to build. The idea was to let the feel of the game steer development toward mechanics worth exploring. This creative phase involved frequent shifts between prototyping and light market research to ensure there was some novelty in the ideas. It was far more effective than sketching on paper, because every small experiment could be immediately played and evaluated.

Attracting junk food in space unexpectedly inspired a shift in perspective—toward something like Slime Rancher in space. Capturing alien creatures by feeding them the right food, layered on top of the scavenging loop, felt both quirky and fresh. 

Since there are so many asteroids in space that you can attract for free, I let myself noodle a bit more. One idea led naturally to another:

✦ Mining ores from asteroids

↳ Led to using ore to upgrade the maximum oxygen capacity of the container

↳ Led to needing ore for ship repairs (finally ditched)

          ↳ Which introduced the concept of damage from meteor impacts

                    ↳ Which led to preparing for space jumps to dodge incoming meteors and respawn space junk with a higher chance of spawning a rare alien creature

          ↳ Led to knocking out alien creatures with asteroids

                    ↳ Which led to feeding specific aliens to lure and capture rarer ones

✦ Adding new junk types

          ↳ Which led to feeding specific junk to capture specific alien creatures

I then faced a key design choice: Should I give players a clear end goal, or leave it as an open sandbox?

I opted for a soft end goal—something that could gently motivate players without compromising the game's atmosphere. My first idea was to show a “total estimated scavenged value” at the end. But it felt shallow. Worse, it encouraged players to rush through the game, undermining the meditative, lonely vibe I had worked so hard to build.

That’s when I realized: the heart of the game wasn’t about speed. It was about soaking in the eerie, quiet beauty of space junk drifting in the void. 

Just before submission, I had the idea: “What if capturing the rarest alien earned you a nickname as your legacy?” It felt like a soft motivation, but still compelling enough to invite replayability. But since I was nearly out of time, I compromised by implementing a nickname system at the end screen, roughly based on what players had collected. It was a fun touch—though admittedly rushed and still in need of refinement, should I ever continue this project.

Many of the noodling mechanics made it into the final prototype through iteration, but more importantly, they helped me shape the design in a practical way. They gradually strengthened my vision of keeping the game sandboxy, where every bit of curiosity or experimentation could be rewarded with more content.

That pretty much sums up the journey of Cosmic Junker Simulator!
Big thanks to the Ludum Dare community—your passion and feedback mean a lot.

🔧 Key Takeaways:

• Online co-op games are risky for game jams unless you’re extremely efficient with networking coding. Debugging eats up precious design time fast.

• Letting mechanics grow from an immersive experience first made design iteration easier and helped the game develop a stronger, more unique identity.

• Giving yourself time to “noodle” really matters, even in a short jam. Some of the most creative ideas surfaced through this playful, low-pressure exploration.