docs: Update plan and progress for subtask 3.5 completion

.auto-claude/specs/001-conceptual-explanations/build-progress.txt

@@ -168,3 +168,98 @@ Implementation details:
 
 Committed: 3c08b45
 Status: ✓ Completed
+
+=== 2026-01-11 - Subtask 3.2 Completed ===
+Added conceptual explanations to all 6 CSS Grid lessons.
+
+Implementation details:
+- Added 'concept' objects to all Grid lessons explaining the 2D grid system, tracks, and cell placement
+- Lesson 1 (Grid Container Basics): 
+  * Explanation of 2D layout system, tracks (rows/columns), 1fr units, and gap property
+  * Diagram showing grid container with 3 equal columns and 2 rows
+  * Container vs Item: display: grid, grid-template-columns, and gap are container properties
+- Lesson 2 (Grid Template Areas):
+  * Explanation of ASCII-art layouts and named grid areas for spanning
+  * Diagram showing visual layout with header, sidebar, content, footer regions
+  * Container vs Item: grid-template-areas (container) vs grid-area (item)
+- Lesson 3 (Spanning Grid Cells):
+  * Explanation of spanning multiple cells with grid-column/grid-row span keyword
+  * Diagram showing 2x2 spanning featured item with auto-flow around it
+  * Container vs Item: grid-column and grid-row are item properties
+- Lesson 4 (Automatic Grid Placement):
+  * Explanation of auto-fit with minmax for responsive grids without media queries
+  * Diagram comparing wide vs narrow viewport behavior
+  * Container vs Item: grid-template-columns with auto-fit is a container property
+- Lesson 5 (Grid Alignment):
+  * Explanation of justify-items (horizontal) and align-items (vertical) alignment
+  * Diagram showing items centered within grid cells on both axes
+  * Container vs Item: justify-items/align-items (container) can be overridden by justify-self/align-self (item)
+- Lesson 6 (Overlapping Grid Items):
+  * Explanation of overlapping items in same cell using explicit positioning and z-index
+  * Diagram showing layered items with z-index stacking
+  * Container vs Item: grid-column, grid-row, and z-index are item properties
+- All explanations are beginner-friendly, 2-4 sentences
+- ASCII diagrams provide visual understanding of grid concepts
+- Clear distinction between container and item properties throughout
+
+Committed: 29c019b
+Status: ✓ Completed
+
+=== 2026-01-11 - Subtask 3.3 Completed ===
+Added conceptual explanations for CSS selector specificity and cascade.
+
+Implementation details:
+- Added 'concept' objects to 4 lessons in lessons/00-basic-selectors.json
+- Lesson 7 (Type + ID): Explains specificity boost from combining type and ID selectors
+  * Shows how p#special has higher specificity than #special alone
+  * Diagram demonstrates both conditions must match (type AND id)
+  * Emphasizes enforcement pattern for IDs on specific element types
+- Lesson 8 (Selector Lists): Explains OR logic and independent matching
+  * Shows how comma-separated selectors are treated independently
+  * Diagram demonstrates each selector matches separately
+  * Clarifies that selectors maintain individual specificity
+- Lesson 9 (Universal Selector): Explains wildcard matching and descendant context
+  * Shows how * matches all element types
+  * Diagram demonstrates descendant relationship with space
+  * Explains difference between global * and contextual .container *
+- Lesson 10 (Specificity): Explains CASCADE and specificity point system
+  * Introduces point system: IDs=100, classes=10, elements=1
+  * Diagram shows specificity calculation with example selectors
+  * Demonstrates how higher specificity wins the cascade
+- All explanations are beginner-friendly, 2-4 sentences
+- ASCII diagrams provide visual understanding of selector matching and cascade resolution
+- Focuses on WHY certain selectors match and HOW conflicts are resolved
+
+Committed: 39f1fb5
+Status: ✓ Completed
+
+=== 2026-01-11 - Subtask 3.5 Completed ===
+Added conceptual explanations to advanced selectors (02-selectors.json).
+
+Implementation details:
+- Added 'concept' objects to all 4 lessons explaining advanced selector concepts
+- Lesson 1 (Element Selectors):
+  * Explanation of DOM traversal and how browser matches tag names
+  * ASCII diagram showing browser checking each element type
+  * Specificity: 0,0,0,1 (lowest - easy to override)
+- Lesson 2 (Class Selectors):
+  * Explanation of attribute matching independent of element type
+  * Diagram showing class matching across different element types
+  * Specificity: 0,0,1,0 (10x stronger than elements)
+- Lesson 3 (ID Selectors):
+  * Explanation of unique ID matching and high specificity
+  * Diagram showing single match and specificity comparison table
+  * Specificity: 0,1,0,0 (100x stronger than classes)
+  * Explains why developers prefer classes over IDs
+- Lesson 4 (Combined Selectors):
+  * Explanation of AND logic (no space between selectors)
+  * Diagram showing both conditions must match
+  * Specificity addition: div.note = 0,0,1,1 beats .note = 0,0,1,0
+  * Emphasizes how cascade resolves conflicts with specificity
+- All explanations are beginner-friendly (2-4 sentences)
+- ASCII diagrams provide visual understanding of selector matching
+- Focus on WHY selectors work and HOW specificity cascade resolves conflicts
+- Explains the fundamental CSS specificity point system throughout
+
+Committed: 3df98fe
+Status: ✓ Completed

.auto-claude/specs/001-conceptual-explanations/implementation_plan.json

@@ -66,36 +66,41 @@
           "id": "3.1",
           "title": "Add concepts to flexbox.json",
           "description": "Add 'concept' objects to all 6 Flexbox lessons. Explicitly explain container vs item distinction. Include simple ASCII diagrams showing axis direction.",
-          "status": "pending",
+          "status": "completed",
-          "notes": ""
+          "notes": "Successfully added 'concept' objects to all 6 Flexbox lessons with:\n- Beginner-friendly explanations (2-4 sentences) for each lesson\n- ASCII diagrams showing main/cross axis direction for visual learners\n- Clear container vs item distinctions for each property\n- Lessons covered: display: flex, flex-direction/flex-wrap, justify-content, align-items, flex (grow), and align-self\n- All concepts follow the schema requirements (explanation required, diagram and containerVsItem optional)\n- JSON validated and committed: 0cf25b6",
+          "updated_at": "2026-01-11T03:44:06.818262+00:00"
         },
         {
           "id": "3.2",
           "title": "Add concepts to grid.json",
           "description": "Add conceptual explanations to CSS Grid lessons explaining the 2D grid system, tracks, and cell placement.",
-          "status": "pending",
+          "status": "completed",
-          "notes": ""
+          "notes": "Successfully added 'concept' objects to all 6 CSS Grid lessons with:\n- Beginner-friendly explanations (2-4 sentences) for each lesson\n- ASCII diagrams illustrating 2D grid system, tracks, and cell placement\n- Clear container vs item distinctions for each property\n- Lessons covered: grid container basics, template areas, spanning cells, auto-fit responsive, alignment, and overlapping items\n- All concepts follow the schema requirements (explanation required, diagram and containerVsItem optional)\n- JSON validated and committed: 29c019b",
+          "updated_at": "2026-01-11T03:48:22.575319+00:00"
         },
         {
           "id": "3.3",
           "title": "Add concepts to 00-basic-selectors.json",
           "description": "Add explanations for CSS selector specificity and cascade. Help beginners understand WHY certain selectors match elements.",
-          "status": "pending",
+          "status": "completed",
-          "notes": ""
+          "notes": "Successfully added 'concept' objects to 4 lessons in 00-basic-selectors.json with:\n- Beginner-friendly explanations (2-4 sentences) for each lesson\n- ASCII diagrams showing selector matching and specificity\n- Clear explanations of CSS cascade and specificity point system\n- Lessons covered: Type + ID combination, Selector Lists (grouping), Universal Selector (*), and Specificity basics\n- All concepts follow the schema requirements (explanation required, diagram optional)\n- JSON validated and committed: 39f1fb5",
+          "updated_at": "2026-01-11T04:08:03.241534+00:00"
         },
         {
           "id": "3.4",
           "title": "Add concepts to 01-box-model.json",
           "description": "Add explanations for the CSS box model - content, padding, border, margin. Include simple diagram showing the layers.",
-          "status": "pending",
+          "status": "completed",
-          "notes": ""
+          "notes": "Successfully added 'concept' objects to all 8 box model lessons with:\n- Beginner-friendly explanations (2-4 sentences) for each lesson\n- ASCII diagrams illustrating the 4-layer box model (content, padding, border, margin)\n- Visual comparisons of margin vs padding, content-box vs border-box, and margin collapse\n- Clear explanations of shorthand notation patterns and individual side targeting\n- Lessons covered: box model components, borders, margins, box-sizing, margin collapse, margin shorthand, padding shorthand, and individual border sides\n- All concepts follow the schema requirements (explanation required, diagram optional)\n- JSON validated and committed: 435381b",
+          "updated_at": "2026-01-11T04:13:22.379924+00:00"
         },
         {
           "id": "3.5",
           "title": "Add concepts to 02-selectors.json",
           "description": "Add explanations for advanced selectors including pseudo-classes and combinators.",
-          "status": "pending",
+          "status": "completed",
-          "notes": ""
+          "notes": "Successfully added 'concept' objects to all 4 lessons in 02-selectors.json with:\n- Beginner-friendly explanations (2-4 sentences) for each lesson\n- ASCII diagrams showing DOM traversal, attribute matching, and specificity comparisons\n- Clear explanations of specificity point system (ID=0,1,0,0, class=0,0,1,0, element=0,0,0,1)\n- Lessons covered: Element selectors, Class selectors, ID selectors, and Combined selectors with specificity\n- All concepts explain WHY selectors work, not just syntax\n- Emphasis on CSS cascade and how specificity resolves conflicts\n- JSON validated and committed: 3df98fe",
+          "updated_at": "2026-01-11T04:19:15.816366+00:00"
         }
       ]
     },
@@ -219,5 +224,5 @@
   },
   "created_at": "2025-01-11T00:00:00Z",
   "updated_at": "2025-01-11T00:00:00Z",
-  "last_updated": "2026-01-11T03:40:28.748942+00:00"
+  "last_updated": "2026-01-11T04:19:15.816374+00:00"
 }