Coding Challenge - Line Rider

This is a physics "game" where a person draws lines that a Line Rider will ride on:
https://www.linerider.com/

A follow up might be to draw lines based on song's rythm - like the bass beat. Here is a video where a Line Rider "rides" a song: https://www.youtube.com/watch?v=qasxqKScOfY

Start by reviewing the Line Rider website and the linked video to understand the proposed physics game and its song-synchronization follow-up. The issue does not name project files, tests, entry points, or a concrete completion condition, so the scope and definition of done would need to be established before implementation.

索引モデルが issue の本文から書いたものです。