Restructure challenges into organized monthly system

- Create challenges/ directory structure with monthly subfolders
- Move October challenge to challenges/October-2025/readme.md
- Create challenge template in challenges/readme.md
- Add November 2025 placeholder in challenges/November-2025/readme.md
- Convert challenges.md to summary page with links and archive
- Update image paths for October challenge screenshots
- Add comprehensive challenge participation and development info

challenges/October-2025/readme.md

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+---
+gitea: none
+include_toc: true
+---
+
+# October 2025 Challenge: "Is it Glass or Clearly Natural?"
+
+### Challenge Overview
+
+Experience the clarity of 3D Fuel's "Clearly Natural" filament in this transparency-focused challenge! Participants will attempt to create the clearest possible print, testing the limits of clear filament printing techniques.
+
+### Challenge Rules
+
+#### Materials & Constraints
+
+- **Filament**: 3D Fuel "Clearly Natural" - Available in two variations:
+  - PCTG (Polyethylene Terephthalate Glycol)
+  - PLA (Polylactic Acid)
+- **Maximum Filament Usage**: 250g per entry
+- **Model Specification**: Cylinder - 25mm diameter × 50mm height
+- **Print Mode**: Vase mode (approximately 6 grams of filament)
+
+#### Competition Categories
+
+- **PCTG Division**: For prints using Clearly Natural PCTG
+- **PLA Division**: For prints using Clearly Natural PLA
+- **Overall Winner**: Best clarity across both divisions
+
+#### Judging Criteria
+
+1. **Clarity & Transparency** (40%): How clear and glass-like is the final print?
+2. **Print Quality** (30%): Surface finish, layer adhesion, and overall structural integrity
+3. **Technique Innovation** (20%): Creative printing techniques to maximize transparency
+4. **Challenge Adherence** (10%): Following material constraints and using supplied model
+
+#### Submission Requirements
+
+- **Model Compliance**: Cylinder must measure 25mm diameter × 50mm height
+- **Vase Mode**: Must be printed in vase mode (single perimeter wall)
+- **Weight Verification**: Should use approximately 6 grams of filament
+- **Documentation**: Include photos showing transparency (with light sources)
+- **Settings Documentation**: Share printer settings used (layer height, temperature, speed, etc.)
+- **Process Notes**: Brief description of techniques used to achieve clarity
+
+#### Evaluation Process
+
+- **Transparency Test**: Prints will be evaluated under controlled lighting conditions
+- **Comparative Assessment**: Side-by-side comparison with actual glass reference
+- **Community Voting**: People's choice award for favorite clear print
+- **Technical Review**: Expert panel assessment of print quality and technique
+
+### Prizes & Recognition
+
+#### Awards
+
+- **PCTG Division Winner**: Recognition + prize
+- **PLA Division Winner**: Recognition + prize  
+- **Overall "Glass Master" Winner**: Grand prize + recognition
+- **People's Choice Award**: Community favorite
+- **Innovation Award**: Most creative clarity technique
+
+#### Documentation
+
+- Winner photos for social media sharing
+- Video documentation of winning techniques
+- Settings and process sharing for community learning
+
+### Timeline
+
+- **Challenge Announcement**: October 1, 2025
+- **Model Specification Released**: October 13, 2025
+- **Submission Deadline**: October 28, 2025
+- **Judging Period**: October 29-30, 2025
+- **Winner Announcement**: October 31, 2025
+
+### Creating the Cylinder Model
+
+#### Using Bambu Studio
+
+**Step 1: Add Primitive**
+
+1. Open Bambu Studio to a new project
+2. Right-click on the build plate
+3. Select "Add Primitive"
+4. Select "Cylinder"
+
+![Adding Cylinder Primitive](../../.images/Oct-Comp-ss1.png)
+
+**Step 2: Resize the Cylinder**
+
+1. Click to resize the cylinder
+2. Uncheck "uniform scale" if checked
+3. Set X and Y to 25mm
+4. Set Z to 50mm
+
+![Resizing Cylinder Dimensions](../../.images/Oct-Comp-ss2.png)
+
+#### Alternative Methods
+
+- **Fusion 360**: Create cylinder sketch, extrude to 50mm height
+- **Tinkercad**: Use cylinder shape, adjust dimensions
+- **FreeCAD**: Create cylinder with specified dimensions
+- **Any CAD Software**: Simple cylinder 25mm diameter × 50mm height