auto-claude: Update build-progress.txt for subtask 4.4

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

@@ -263,3 +263,74 @@ Implementation details:
 
 Committed: 3df98fe
 Status: ✓ Completed
+
+=== 2026-01-11 - Subtask 4.1 Completed ===
+Added conceptual explanations to colors module (03-colors.json).
+
+Implementation details:
+- Added 'concept' objects to all 4 lessons explaining color theory and formats
+- Lesson 1 (Setting Background Colors):
+  * Explanation of hexadecimal color format and RGB channel encoding
+  * Diagram breaking down #e0f7fa into RGB components (red=224, green=247, blue=250)
+  * Comparison table showing hex vs RGB vs HSL formats
+  * Explains why hex is popular (compact, 16.7M colors, browser consistency)
+- Lesson 2 (Text Color and Contrast):
+  * Explanation of color contrast ratios (1:1 to 21:1 scale)
+  * WCAG accessibility guidelines (4.5:1 normal text, 3:1 large text)
+  * Diagram comparing contrast ratios with visual examples
+  * Shows how HSL format helps choose contrasting colors by varying lightness
+- Lesson 3 (CSS Gradients):
+  * Explanation of color interpolation and color stops
+  * Shows how browser calculates intermediate RGB values proportionally
+  * Diagram illustrating gradient progression from 0% to 100%
+  * Explains why gradients use background-image (they're generated images)
+- Lesson 4 (Background Images & Repeat):
+  * Explanation of background layering (content > image > color > parent)
+  * Shows how background-color shows through transparent image areas
+  * Diagram illustrating 4-layer background system
+  * Explains tiling behavior and positioning coordinate system
+- All explanations are beginner-friendly (2-4 sentences)
+- ASCII diagrams provide visual understanding of color concepts
+- Focus on WHY different color formats exist and WHEN to use each
+- Covers fundamental color theory: RGB color model, contrast accessibility, interpolation
+
+Committed: efbd9f1
+Status: ✓ Completed
+
+=== 2026-01-11 - Subtask 4.4 Completed ===
+Added conceptual explanations to transitions and animations module (06-transitions-animations.json).
+
+Implementation details:
+- Added 'concept' objects to all 4 lessons explaining how CSS transitions interpolate values and keyframe animation timing
+- Lesson 1 (Transitions):
+  * Explanation of value interpolation at 60fps and RGB channel calculations
+  * Diagram showing time progression from black to white with intermediate gray values
+  * Formula breakdown: value = start + (end - start) × progress
+  * Browser rendering process: detect change, start timer, calculate frames, interpolate, repaint
+  * Lists which properties can be transitioned (colors, lengths, transforms, opacity)
+- Lesson 2 (Timing Functions):
+  * Explanation of easing functions and Bézier curves controlling rate of change
+  * Visual diagrams comparing linear, ease-in, ease-out, and ease-in-out curves
+  * Shows how timing functions mimic real-world physics (acceleration/deceleration)
+  * Includes cubic-bezier values for all common timing functions
+  * Real-world analogies (car accelerating, braking, between stop signs)
+- Lesson 3 (Keyframes):
+  * Explanation of multi-step animations with keyframe snapshots at specific percentages
+  * Timeline breakdown showing interpolation between 0%, 50%, and 100% keyframes
+  * Visual representation of bounce animation with arc diagram
+  * Comparison of keyframes vs transitions (multi-state vs single state change)
+  * Explains implicit keyframes when 0% or 100% are not defined
+- Lesson 4 (Animation Properties):
+  * Explanation of animation-delay, animation-iteration-count, and animation-fill-mode
+  * Complete timeline diagram showing delay, iterations, and fill-mode behavior
+  * Detailed breakdown of fill-mode values: none, forwards, backwards, both
+  * Visual representation of element state at each phase
+  * Staggered animation examples and negative delay use cases
+  * Animation shorthand syntax breakdown
+- All explanations are beginner-friendly (2-4 sentences)
+- Detailed ASCII diagrams illustrate interpolation algorithms, timing curves, and animation timelines
+- Focus on HOW browsers calculate intermediate values and WHEN to use each feature
+- Covers fundamental animation concepts: interpolation, easing, keyframe timing, playback control
+
+Committed: 443ec4c
+Status: ✓ Completed