Updating Gun Rocket through 10 years of Unity Engine

Join me as I update a project through 10 years of Unity editors. Along the way I will talk about my process, Unity tips and tricks, and the tech changes of Unity Engine - several of which I observed firsthand while working at Unity.

About 10 years ago I made Gun Rocket.

It was early in my game development journey. I had released 5 prototype games on Game Jolt, and it was time to sit down and make something worth paying for. I started with the idea "What if n++...but with the Asteroids ship?"

Development took about a month. The result was a game with 100 levels, multiple ships with different stats to pilot, and even a LAN multiplayer combat mode. Gun Rocket also stands out as my most lucrative personal project. After a successful Steam Greenlight process I was approached and licensed the Steam distribution rights for the game for a few years.

Recently I was reflecting on my game development journey. I tried to boot up Gun Rocket to play it. But it refused. No matter how hard I clicked the game would not open. The log is empty. I guess some driver or Windows API just doesn't work anymore.

So it is time to roll up my sleeves and bring Gun Rocket into 2026. Come along won't you? I could use the company.

Gun Rocket won't launch. What to do?

Let's start by opening the game in Unity Editor. We'll test the game in its current editor version and re-acquaint ourselves here before moving on. The version of a Unity project is stored in /ProjectSettings/ProjectVersion.txt. It's a simple file with a simple purpose. Here's what I see:

m_EditorVersion: 5.5.0f3

Looking back at the git history of this file, I can see that I actually developed the game in 4.6.0p1 in 2015. The ProjectVersion file was created when migrating from 4.6 to 5.5 in 2018 hoping it would fix a bug (it didn’t). So there's our first interesting factoid about how Unity has changed. Crazy how time flies.

Anyway! Looks like Gun Rocket was most recently developed in Unity 5.5.0f3. The current Unity tech stream is 6.5 beta. That doesn't seem so bad! Just one major version bump, right?

WRONG!

Some time around 2017, Unity decided that its numbering was not corporate-friendly. At that time they were trying to expand from gaming into more verticals. I guess corporations love versioning their software by year, so that's what Unity did. It makes the messaging about long-term support easier. Let's say Unity supports a release for 3 years. When does that end? It's much easier to talk about that for Unity 2017 (2017 + 3 = 2020) than for Unity 5.5 (???).

Nowadays Unity is back to simple numbers. Today’s major version number is 6. At least...that's what the website says. Unity version numbers now look something like 6000.4.1f1. I find this hilarious. It reminds me of Loony Tunes technology naming. Roadrunner Catcher 3000 anyone? Again, there is a good reason for this. 6000 > 2023. 2023 is Unity's last year-named version. So all of the version sorting code will continue to Just Work TM. A Good Reason. But I still find it funny.

So I open Unity Hub and look for 5.5.0f3. It's not one of the readily available options. Unity presents Official Releases (long-term support and the latest supported minor release 6000.4.1f1), Pre-releases (currently just the 6000.5.0b1 beta), and ArChIvE. We'll be spending a lot of time in the archive. I like to think of it as the back room in the basement where folks store things they just can't bear to part with yet. It's super excellent that all of these versions are kept around. It means my ambition to bring Gun Rocket into 2026 has legs - if only barely. The archive only goes back to Unity 5. Good thing I upgraded from 4.6 in 2018!

Wow, all this history and we haven't even opened the editor yet. Let's try that now.

Uh Oh. Gun Rocket won't open in 5.5.0f3.

It does the same thing as the game build on Steam: just closes with no information in the log. Shoot.

Some Google research tells me this might be related to the license check. Unity 5 pre-dates Unity Hub. So sure, it makes sense that it could be a license check issue. I try to open from the Unity.exe rather than through Hub as suggested. No luck.

Ok then, let's try a newer version. I wanted to verify the game in 5.5, but I guess I am out-of-luck. I nab the most recent Unity 5: version 5.6.7f1. Again, it doesn't launch from Unity Hub, but that's what I expect at this point. What about launching from the Unity.exe?

Wow, what a wave of nostalgia this is. Familiar and yet…feels old? Unity 5.5 absolutely feels dated to my eyes. I am sure it felt modern and sleek at the time, but opening it now...it just doesn't. One thing I remember is that the UI doesn't scale with Windows Display Settings. I have my screen UI scaled to 125%. Unity is absolutely not respecting that and all the UI feels small.

Another thing I notice here is the Standard Assets folder. If I recall correctly you could choose to put StandardAssets in your project when you created it. It includes some particles, scripts for camera and interactions, and a toon shader. Boy, look at this fire!

Cool cool cool. I have Gun Rocket open. Let's pay it forward and leave a comment on Unity Forums and then move on.

So Let’s Play!

I am grinning from ear to ear. The music was created by my friend Peter Dmitrieff and boy does it still hit. What a great nostalgia hit!

I don't have any saved game data on this computer so I move through the tutorial and then into the first level. Care to watch me flail around?

Aaaand...I explode after loading into the first level? That's not good.

After trying a few times I realize if the ship isn't moving for about 0.5 seconds it explodes. Has that bug existed all this time? Oh bother. I hope not!

Do I want to tackle bugs as they come, or should I focus on the engine migration and then tackle bugs? For better or worse I decide to keep track of bugs and fix them at the end. I'll have enough work just migrating the game through the Unity Engine changes to come without giving myself more to do in the middle.

I play a bit more to make sure that nothing is horribly broken. The save system works. I play through maybe 15 levels. I can change ships. Settings changes work. Gun Rocket doesn't have a huge UI/UX surface to cover. I play long enough to feel good about it and then decide to move on.

The Plan

Knowing all of the tech changes to Unity Engine over the years, I decide my strategy is to step one major version at a time.

5.6.7f1 → 2017.4.40f1

We get off to a great start. This transition was completely uneventful. I even had 2017.4.40f1 installed already.

Looking at the git commit…really nothing happened. ProjectVersion.txt updated

Oh, and we have a new file called UnityPackageManager/manifest.json. This must be where Unity introduced the package manager. Hilarious: it’s completely empty. I don’t remember ever seeing this before. It’s so beautiful.

{
"dependencies": {
}
}

Unity introduced package manager as the engine grew to serve at least these 3 purposes that I can remember off the top of my head:

Get C# code out of the engine core to where folks could see it and modify it if they need to.

Allow people to select which Unity packages they wanted…or didn’t! As the engine features grow allow folks to opt in/out so they can be in control of their disk space.

Provide a standard for C# modules to be used by 1st and 3rd party teams.

I was at Unity during the great packagification. The goals were noble, but it turns out keeping dependencies between all the teams’ various packages became its own daily bother. Maybe I’ll write about that some time, but this isn’t that post.

Anyway, this upgrade was nothing. This is going to be easy.

Narrator: chuckles

2017.4.40f1 → 2019.3.15f1

I’m feeling pretty full of myself, so I skip Unity 2018. I’ve got Gun Rocket on source control. I can always revert if I need to. I just so happened to have 2019.3.15f1 i