I Entered an AI Game Competition

What the report says

This article is the third entry in the series, following Making a Game with Vibe Coding: Part 1 and Part 2.There was good news.'Twilight Mountain Defense,' a game I created, won the Grand Prize at our 'In-House AI Game Development Contest 2026.' Since I happened to be serializing articles under the theme of 'Making a Game with Vibe Coding,' this contest brought an unusually heavy burden.Although I had never learned game development or coded before, I felt I had put in enough hard work to really want an award. The result turned out far better than expected, and to be honest, I was thrilled.However, the joy was short-lived."Congratulations.

Also, an AI game development event is taking place in August called 'OpenAI Game Builders Seoul.' Why don't you enter it with that game?""Pardon?""I'll give you work hours for it and support you with AI tools.""...Got it."And just like that, game development, which I thought was finished, began anew.Deciding to Remake the Award-Winning Game from ScratchI was flustered, but I didn't hate the idea.Making the first game was genuinely fun. Iterating through conversations with AI, seeing the project gradually take shape, and realizing the things I had imagined one by one completely absorbed me.So when given the opportunity to make a game again with guaranteed work hours, I had no reason to refuse.The problem was time.

There were only about two weeks left until submission. Looking at the competition criteria, simply tweaking an existing game didn't seem like enough.The event required submitting a game prototype developed with Codex along with the development experience. While using an existing project was allowed, 'Twilight Mountain Defense' was primarily made using Claude. I decided to use this opportunity to rebuild it from scratch using Codex.Since I was rebuilding it anyway, I decided to try something new. Instead of creating a single HTML file, I chose to use a proper game engine. I selected the Godot Engine, which has been frequently discussed among indie developers recently.My interest in Godot came from an interview I conducted in the past with a solo developer.

Key details

Having left Nexon to develop games independently, he praised Godot as quite a solid engine for indie game creation. The thought of trying it out someday had stuck with me ever since.Of course, I don't know how to use a game engine (laughs). So it was only possible if AI 'did it for me.' Fortunately, Codex replied that it could create a web game using Godot Engine.Now, there were two goals to achieve over the next two weeks.First, remake 'Twilight Mountain Defense' from scratch using Codex.Second, complete a browser-executable game using Godot Engine for the first time.And so, the second game development project began.Coding and Image Generation in One Place… Why Codex Was GreatWorking with Codex was far better than expected—to the point where I found myself thinking, "It can even do this?"First, making a game with Godot Engine.

I didn't even know the difference between nodes and scenes. After downloading the Godot Engine, I provided Codex with the installation directory and project path. Codex then ran the engine directly to carry out the work. All I did was download the engine, yet before I knew it, I was building a game with a proper engine. Haha.Another great thing was the seamless workflow. When making the original, I entrusted the code and game systems to Claude while generating graphics with a separate AI like Grok. Switching back and forth between two AIs was extremely tedious.

Downloading images, removing backgrounds, and adjusting sizes were all manual labor. I had to feed those images back to Claude for feedback and repeat the production process multiple times.With Codex, everything from character design to background removal, resizing, applying graphics in-game, and modifying code flowed seamlessly within a single workflow. When I requested, "Make the Pyromancer throw flames and the Cryomancer spread ice," it modified not only the visuals but also the attack effects and damage mechanics altogether.There was also a huge difference in graphical work.Previously, I had to manually remove the backgrounds from AI-generated images.

More from the announcement

Lacking professional image-editing skills, background colors often remained along character outlines, or parts of hair and weapons got cut off. Zooming in on images inside the game made those flawed crops stand out even more clearly.This time, I left image creation, post-processing, and in-game application all to Codex.