Advent Mirror is copyright 2022 by Andrew Plotkin (firstname.lastname@example.org). It may be distributed for free, but not sold or included in any for-profit collection without written permission from the author.
Advent Mirror is sort of a sequel to Advent Door, but you don't need to play that game first. In fact, there's nothing to say which of them comes first. For all I know, Advent Door is the sequel.
This game was written for the Confounding Calendar 2022, a collaborative Advent Calendar puzzle collection. Most of the games in this project are grid-based puzzles (typically PuzzleScript), but I decided to enter a parser game.
The only provided theme was a shared color palette. If you play Advent Mirror on this web site, you'll see that I used the palette for displaying the game text. If you play in another interpreter, you won't get the colors. (Don't worry, they're purely decorative.)