itch.io

That sounds about right. Graphics are, to put it gently, limited.

I had the extra line below the code because the site's copy-paste is a little shaky on line endings. But I can see how that would cause other problems. A semicolon would eat anything typed before hitting Enter. A colon inserts more hex, or... treats an address as reading from tape? I don't want to end with a 300R, because the game starts right up, and the Load interface obscures it.

Ending with a 300 in the buffer should better handle whatever people do with my vague instructions.

In my defense (for the instructions, unrelated to the game) it is a stretch to say this machine had published software. Concise explanations are a step above providing a soldering diagram. 

You hit things below the ground floor because you're underground.