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Caelium Alpha was something that I always wanted to make, interactive software for making imaginary solar systems. I think this was my more favorite Ludum Dare event yet. I made something decently playable within the 72 hours, but also made a Post-LD build that has more features and bug fixes.

I really appreciate all the people who played the game and gave feedback! The feedback will help me greatly in determining what features to add to the game and what should be fixed. I intend to keep making this after the event’s over, but it will have to progress very slowly.

What Went Well

• I’m happy with the complex object hierarchy that allows each of the planets to orbit around the star with different orbit speeds and rotations. It can even support tilt (like the planet Uranus), but this was an experimental feature that was not released as of yet.
• The UI could always improve, but I don’t use Unity’s UI features that much, so having the changeable UI with sliders feels like an accomplishment.
• Planet selection with the mouse. Doesn’t sound like a big deal, but it’s fundamental in order for this game to work.
• The particle effects help with depth perception and adds visual cues to the game.
• Got great feedback from the Ludum Dare community. Thanks again!
• Object-based data system that allows stars, planets, and moons to have adjustable properties that they all have in common while also having unique features.
• Decoupling between a planet’s data and the scripts controlling the properties of a planet.
• (In the Post-LD Version) My implementation of auto-padding between planets allow planets to change size or have additional moons without other planets colliding them.
• (In the Post-LD Version) Being able to use a musical piece from Stephen Tanksley. Adds nice atmosphere to the game!

What Went Badly

• Towards the end of the jam, I encountered a weird bug where multiple planets would spawn the more you add planets. This bug was fixed because someone told me that I could fix important bugs after the jam. The bug was caused by a prefab referencing itself, which is apparently a big no-no in Unity; I wrote a blog post explaining this problem in depth.
• Did not have time for sounds in the LD Version, but they are fortunately available in the Post-LD Version.
• Many people were not fans of the camera controls (especially zooming). I myself do not like my own camera implementation, but I couldn’t spend the entire jam making the perfect camera controls ;p
• My code organization was okay, but it could still use a minor refactor if I intend to develop this game further.
• Could not get moons implemented during the jam, but fortunately they are available in the Post-LD Version.

Features I’ll Consider in the Future

These desired features are not listed in any particular order, and are only up for consideration. They may or may not eventually be implemented:

• The ability to tilt a planet’s orbit and rotational axis (these are partially implemented, not made available to the user).
• More music and sound effects
• More realistic orbital speed dynamics based off orbital distance
• Better camera movement controls (including better zoom (no more fisheye), “anchoring” on selected objects, and top-down view)
• Different types of planets (rocky, terrestrial, gas giant, etc.)
• Rings around planets
• Ability to remove planets and moons
• Procedural textures with adjustable color properties (very long term feature)
• Procedural space skyboxes (very long term feature)
• Realistic rim shader for planets and moons
• Flare and light effects for stars
• Rename planets, stars, and moons
• Pause planetary movements

Once again, I thank everyone who played the game and gave feedback. If you want to follow further development, you can either follow me on Twitter, follow the game on Itch.io, or bookmark Caelium Alpha’s project page on this blog.

I am happy to announce that the Post-LD Edition of Caelium Alpha is now avaliable on Itch.io. Last post, I mentioned about a bug where planets would clone multiple times. Fortunately, that bug was fixed, and I also added the ability to add moons, which wasn’t supported in the original Ludum Dare entry.

The Post-LD Edition also features a soundtrack from the composer Stephen Tanksley (great music for modern games) and sound effects from Glitchmachines. Audio really does make a big difference!

If you are interested in reading more about the original Ludum Dare version of Caelium Alpha, you can read about it on its Ludum Dare page.

On the previous weekend was the 38th Ludum Dare game jam, which has now been going on for 15 years. This time around, the theme was “A Small World”. As I thought about how to design a game around a small world, I remembered a project that I always wanted to do.

A little history first, I always wanted to make a “game” involving building your own solar system (or planetary system, which is the general term). It would always be more of a sandbox, akin to Minecraft or SimCity. I’ve called this game idea Caelium (which originates from a word “caelum” for “sky or heavens”). I’ve wanted to make a serious prototype of this game, but for various reasons I couldn’t (life, college, grad school, etc.)

So concerning the game jam theme, I figured that I could probably make Caelium resemble “a small world” by trying to imitate an orrery, which is a model of the solar system. By participating in this game jam, I finally made serious progress with this idea. Since it’s still early, I called the game Caelium Alpha.

Unfortunately, the current version of the game has a strange bug where multiple planets spawn when trying to spawn one planet. This was due to a prefab reference problem in Unity I mentioned in another post. I intend to make an improved version of Caelium Alpha that fixes this problem and also add the ability to spawn moons (which is currently not supported).

If you want to try out the game prototype, you can go to the game’s Ludum Dare page, or the game’s Itch.io page.

In Unity, I wanted to set up a situation where there is a prefab, and it contains a script, and that script references back to the prefab. The reason for this strange setup was because, once cloned, that GameObject can keep cloning itself as instructed by the script.

When I started cloning this prefab, I discovered that mutiple objects started popping up (instead of one). I tried breakpoints and logging messages, but I couldn’t figure out why many clones were popping up from one invocation.

I eventually went into the object hierarchy and found that the root prefab clone had a very important GameObject reference mysteriously changed. The original prefab would have this reference pointing to itself, but when cloned in the scene, the clone would no longer point to the original prefab, but instead to the clone itself, automagically!

After a ton of searching, I found a discussion on the Unity Forums pertaining to this problem. It was here that I found out that any prefab that references itself and then get cloned, the clone will reference itself, not the original prefab.

I frankly consider this unexpected/undesireable behavior, but on the forum thread, someone from Unity said that it was by design. Perhaps I can understand that the underlying implementation of Unity is complex, and they had to make decisions that can look strange to an outsider. But I still would consider this to be a bug, because it cost me a ton to time to fix this issue. I was working on a game called Caelium Alpha when I encountered this problem, which happened around the last 2 hours. I was not able to fix it before time was up.

So the moral of the story is that you should never have a prefab that references itself in its own scripts. It can cost you your development time!

If you are curious to know a workaround, personally I just resorted to loading the prefab from a Resources folder in the Unity project, and loading the prefab with Resources.Load(). This is actually not my prefered way to solve a problem like this, but I decided to go for it, because there was only 1 prefab I wanted to clone, not a hundred different prefabs.

One of the hardest classes in grad school was a class where you make Space Invaders. You would think that would be easy, but it was actually very difficult (although rewarding in the end). From basically nothing (other than a barebones OpenGL graphics API written for C#), students were to recreate the famous game Space Invaders.

You can read more about that at the project’s page, and get the source code from there too (Windows only).

I made a game a while ago for Ludum Dare called Gyra. It’s my most polished Ludum Dare game yet. You can play it here.

You can see what other Ludum Dare games I made here.

I recently participated in the 33^rd Ludum Dare online game jam.

My entry was called Galactic Space Crusher. You play as a giant spaceship who must wipe out fleets of enemies with an arsenal of weapons.

I couldn’t develop it enough the way I wanted, but if I decide to develop this, I’ll try to make it much better.