I have released EffekseerForYMM4. This is a plugin that allows you to use effects created with the game effect creation tool “Effekseer” directly as video decorations in YMM4 (Yukkuri Movie Maker 4).

The official Effekseer samples are CC0 (Public Domain), so they can be used as video materials as is. Please note that I apologize if YMM4 crashes due to the use of this plugin.

Ideally, debugging by continuously playing effects within an explanation video would improve quality, but finding the video template I used before is a hassle (I’m finding it hard to get started), so I haven’t gotten around to that.

Thoughts on Development Using LLMs

I used LLMs for development this time, but there were two major points where things didn’t go smoothly.

1. Lack of Domain Knowledge and Context Issues

Effekseer is a popular repository with 1.7k stars, and YMM4 is also popular software among “Yukkuri Jikkyo” (Yukkuri commentary) creators in Japan. However, perhaps because YMM4 is unique to the Japanese cultural sphere, the LLM had only vague domain knowledge about both, leading to issues where it couldn’t generate code well.

I think I was able to prevent the LLM from getting lost by extracting only the “necessary parts” from libraries and sample code and providing them. Looking back, I should have summarized the specifications in AGENTS.md, but at the time, I didn’t grasp which parts of the code were being used, so I couldn’t give appropriate instructions. deepwiki was quite useful for understanding the repository. I also wanted to use codewiki, but I gave up because my repository registration application was not accepted.

2. Feedback Loop for Video and Audio

The next problem is debugging video and audio. Currently, LLMs cannot directly check “visuals” or “audio,” so a process was essential where a human looks and listens, and then returns that result as feedback in words.

Companies are claiming that “anyone will be able to develop software” this year, but I’d be happy if this part of human-mediated feedback (visual and auditory confirmation) also evolves.

LLMs Used: In addition to Gemini, Codex, and Claude available from Antigravity, I also used Gemini CLI and the free period of Codex.