A few months ago, some of us started tossing around the idea of a new collaborative IF project. Something like Cragne Manor, although more sensibly scaled. (That is: much smaller.)
The goal was an IF Advent Calendar -- pun intended! -- with one game for each day of Advent season. Since an Advent calendar has you opening a door each day, we'd create games in the old Planescape setting: Sigil, the "City of Doors".
The project wound up not coming together. So I'm posting my game on its own today. (A misplaced calendar day would turn up on February 29th, right?)
Advent Door is a snack-sized IF puzzle written in Inform 7. There's not much to it beyond the single puzzle. Imagine a series of games like this, each one ending at a planar portal that leads to the next game in the series.
The only other Advent Calendar game to be released -- as far as I know -- is Gateway of the Ferrets by Feneric.