Complete 3.3.1: Mobile Layout Optimization - Implemented mobile-first redesign with touch-friendly navigation and responsive chat overlay behavior.

UI_UPDATE.MD

@@ -338,10 +338,12 @@ Always come back and update UI_UPDATE.MD once complete with task and task item.
 
 ### Sub-task 3.3: Mobile-First Redesign
 
-#### 3.3.1: Mobile Layout Optimization
-- [ ] Redesign mobile interface prioritizing content
-- [ ] Implement touch-friendly navigation
-- [ ] Create mobile-specific component layouts
+#### 3.3.1: Mobile Layout Optimization - COMPLETED 9/29/2025
+- [x] Redesign mobile interface prioritizing content
+- [x] Implement touch-friendly navigation
+- [x] Create mobile-specific component layouts
+
+**Notes:** Implemented comprehensive mobile-first responsive design. Updated layout.css to use BEM class names, added vertical stacking layout for mobile (flex-direction: column), chat slides up from bottom as modal overlay on mobile instead of collapsing to the side. Enhanced touch-friendly navigation with 44px minimum touch targets already in place. Updated ui-controls.js to handle mobile chat overlay behavior. Desktop remains side-by-side layout while mobile prioritizes video content with chat on-demand.
 
 #### 3.3.2: Touch Interaction Optimization
 - [ ] Ensure 44px minimum touch targets