Update challenges for December 2025 and add January 2026 placeholder

challenges.md

@@ -9,31 +9,29 @@ Welcome to our monthly 3D printing challenges! Each month features a unique them
 
 ## Active Challenge
 
-### November 2025: "Wait, This Was Printed?"
+### December 2025: "Bring Your Test Models"
 
-**Theme**: Achieving the smoothest, most layer-line-free surface finish possible.
+**Theme**: Sharing and comparing printer calibration and test models.
 
 **Key Details**:
 
-- **Model**: 25mm x 25mm x 25mm cube (2 walls, 0 top layers, 0% infill)
-- **Goal**: Create a surface so smooth it doesn't look 3D printed
-- **Judging**: Based solely on surface smoothness and lack of visible layer lines
+- **Model**: Your favorite test/calibration print (Benchy, Cube, Torture Test, etc.)
+- **Goal**: Share why you use it and what it helps you tune
+- **Voting**: Group vote for "Best Test Model" (Usefulness, Uniqueness, Coolness)
 
 **[View Full Challenge Details](https://meetup.fargo3d.com/Fargo3d/3DPrintMeetup/wiki/Current-Challenge)**
 
 ## Upcoming Challenge
 
-### December 2025: "Bring Your Test Models"
+### January 2026: "[Challenge Name TBD]"
 
-**Theme**: Sharing and comparing printer calibration and test models.
-
-**Status**: To be announced at December 10th Meetup.
+**Status**: Planning in progress
 
 **Expected Timeline**:
 
-- **Announcement**: November meeting (November 12th, 2025)
-- **Submission Period**: TBD
-- **Judging**: TBD
+- **Announcement**: January meeting (January 2026)
+- **Submission Period**: February 2026
+- **Judging**: February 2026
 
 **[View Challenge Placeholder](./challenges/November-2025/readme.md)**