Custom Arcade Game JavaScript Optimization

I've developed a simple arcade game in HTML, and I need it remade in JavaScript with a keen focus on efficiency. The original version is several MB, and I need it rebuilt to be under 400KB. You will have access to the original game's source code, so you can use that as a reference. The remake should be exactly the same as the original.

Ideal Skills:
- Experience in game development
- Proficient in JavaScript
- Skilled in file size optimisation

If you have the relevant experience, let's discuss this project further!