Complete 3.1.2: 12-Column System - Implement comprehensive 12-column CSS Grid system with responsive variation classes, expanded gap spacing system, and grid utility classes for common patterns

UI_UPDATE.MD

@@ -286,10 +286,18 @@ Always come back and update UI_UPDATE.MD once complete with task and task item.
 
 **Notes:** Added comprehensive CSS Grid utility classes to utilities.css including grid template columns, spanning utilities, alignment classes, and auto-fit/auto-fill responsive grids. The current flexbox implementation was analyzed and determined that main layout structures (theater-container, video-section) are appropriately using flexbox for their use cases. Grid utilities provide foundation for future responsive layouts and component arrangements.
 
-#### 3.1.2: 12-Column System
-- [ ] Create responsive grid variation classes
-- [ ] Implement grid gap and spacing system
-- [ ] Add grid utility classes for common patterns
+#### 3.1.2: 12-Column System - COMPLETED 9/29/2025
+- [x] Create responsive grid variation classes
+- [x] Implement grid gap and spacing system
+- [x] Add grid utility classes for common patterns
+
+**Notes:** Implemented comprehensive 12-column CSS Grid system in utilities.css with:
+- Expanded grid column spans (col-span-5 through col-span-12)
+- Added col-start-* and col-end-* utilities for precise column positioning
+- Implemented responsive grid classes (.sm\:grid-cols-*, .md\:grid-cols-*, etc.) for all breakpoints
+- Enhanced gap system with gap-*, gap-x-*, and gap-y-* utilities
+- Added grid-flow utilities and additional alignment classes
+- Created responsive grid variation classes for sm (640px+), md (768px+), lg (1024px+), xl (1280px+), and 2xl (1536px+) breakpoints
 
 #### 3.1.3: Layout Utilities
 - [ ] Create container and wrapper utilities