The game itself is built using 2D matrices to track positions of different ASCII characters, with movement simulated by moving the characters across the rows/columns of the matrix. I ended up saving a lot of space by using programmatic sound effects via the AudioContext web API rather than using mp3 sound files, which was pretty cool to learn. Also, getting the jumps in the game to feel somewhat "moon-like" was sorta fun, and I think make it a bit more challenging.
Anyways, the source code is all available here: https://github.com/benbusby/tiny-moon-runner. Looking forward to seeing everyone else's (likely more complicated) submissions!