feat: Complete 2D Visual Overhaul - Isometric to Flat Top-Down

- NEW: Flat2DTerrainSystem.js (375 lines)
- NEW: map2d_data.js procedural map (221 lines)
- MODIFIED: GameScene async create, 2D terrain integration
- MODIFIED: Player.js flat 2D positioning
- MODIFIED: game.js disabled pixelArt for smooth rendering
- FIXED: 15+ bugs (updateCulling, isometric conversions, grid lines)
- ADDED: Phase 28 to TASKS.md
- DOCS: DNEVNIK.md session summary

Result: Working flat 2D game with Stardew Valley style!
Time: 5.5 hours

docs/2.5D_TERRAIN_GUIDE.md

@@ -0,0 +1,159 @@
+# 🏔️ 2.5D TERRAIN SYSTEM - COMPLETE DOCUMENTATION
+
+## 📋 OVERVIEW
+
+Complete 2.5D terrain system with procedural hills, height-based collision, and visual polish.
+
+---
+
+## ✅ PHASE 1: HEIGHT GENERATION & VISUALIZATION (COMPLETED)
+
+### Implementation:
+- **Height Generation:** Perlin noise (0.05 frequency) generates smooth hills
+- **Height Range:** 0-5 discrete levels
+- **Visual Effects:**
+  - **Tint:** `0x666666` (dark valleys) → `0xffffff` (bright peaks)
+  - **Scale:** `1.0x` → `1.5x` (50% size increase on peaks)
+  - **Y-Offset:** `0px` → `-75px` (massive elevation)
+
+### Code Location:
+- **Generation:** `TerrainSystem.js` - `generateChunk()` line ~504
+- **Visualization:** `TerrainSystem.js` - `updateCulling()` line ~1031
+
+---
+
+## ✅ PHASE 2: WALKABILITY CONSTRAINTS (COMPLETED)
+
+### Implementation:
+- **Height-Aware Collision:** Can't walk over height difference > 1
+- **Cliff Detection:** Checks `Math.abs(toHeight - fromHeight) > 1`
+- **Console Feedback:** Logs "🏔️ Blocked by cliff!"
+
+### Code Location:
+- **Collision Check:** `TerrainSystem.js` - `isSolid(x, y, fromX, fromY)` line ~1262
+
+---
+
+## 🎨 PHASE 3: VISUAL POLISH (OPTIONAL)
+
+### Planned Features:
+
+#### 1. **Cliff Edge Sprites**
+```javascript
+// Detect cliff edges (height diff > 1)
+if (heightDiff > 1) {
+    // Add cliff edge sprite between tiles
+    const edgeSprite = this.add.sprite(x, y, 'cliff_edge');
+    edgeSprite.setRotation(angleToNeighbor);
+}
+```
+
+#### 2. **Shadow Effects**
+```javascript
+// Add shadow to lower tiles near cliffs
+const shadowAlpha = Math.min(heightDiff * 0.2, 0.6);
+const shadow = this.add.rectangle(x, y, tileWidth, tileHeight, 0x000000, shadowAlpha);
+```
+
+#### 3. **Gradient Blending**
+```javascript
+// Smooth color transitions between heights
+const neighborAvgHeight = (h1 + h2 + h3 + h4) / 4;
+const blendedTint = interpolateColor(currentTint, avgTint, 0.3);
+```
+
+---
+
+## 🎮 USAGE
+
+### Reset World (New Seed):
+```javascript
+// In browser console (F12):
+localStorage.clear();
+// Refresh → New procedural world with hills!
+```
+
+### Test Height System:
+```javascript
+const scene = window.gameState.gameScene;
+const tile = scene.terrainSystem.getTile(50, 50);
+console.log('Height:', tile.height); // 0-5
+```
+
+### Test Collision:
+```
+1. Walk around the map
+2. Try to climb steep hills (height diff > 1)
+3. Console: "🏔️ Blocked by cliff!"
+```
+
+---
+
+## 📊 CURRENT STATUS
+
+| Feature | Status | Description |
+|---------|--------|-------------|
+| Height Generation | ✅ Complete | Procedural hills with Perlin noise |
+| Visual Height | ✅ Complete | Tint + Scale + Y-offset |
+| Walkability | ✅ Complete | Height-based collision |
+| Cliff Edges | ⏳ Optional | Visual borders (Phase 3) |
+| Shadows | ⏳ Optional | Shadow effects (Phase 3) |
+| Gradients | ⏳ Optional | Smooth blending (Phase 3) |
+
+---
+
+## 🔧 CUSTOMIZATION
+
+### Adjust Height Intensity:
+```javascript
+// In TerrainSystem.js - generateChunk()
+const heightNoise = this.noise.noise(x * 0.05, y * 0.05);
+const rawHeight = (heightNoise + 1) * 2.5; // Change 2.5 to 5.0 for more extreme (0-10 range)
+```
+
+### Adjust Visual Effects:
+```javascript
+// In TerrainSystem.js - updateCulling()
+const tintValue = 0x666666 + (height * 0x333333); // Adjust contrast
+const scaleBonus = 1.0 + (height * 0.1); // Adjust size (0.1 = 10% per level)
+const elevationOffset = -(height * 15); // Adjust elevation (15px per level)
+```
+
+### Adjust Walkability:
+```javascript
+// In TerrainSystem.js - isSolid()
+if (heightDiff > 1) { // Change to 2 for more permissive, 0 for stricter
+    return true; // Blocked
+}
+```
+
+---
+
+## 🐛 TROUBLESHOOTING
+
+### Hills not visible?
+1. Clear localStorage: `localStorage.clear()`
+2. Refresh page
+3. Check console for "🏔️ HEIGHT GENERATION" logs
+
+### Can walk through cliffs?
+1. Ensure player movement uses `terrainSystem.isSolid(x, y, fromX, fromY)` with 4 parameters
+2. Check console for "🏔️ Blocked by cliff!" messages
+
+### Tiles look glitchy?
+1. Reduce elevation offset (try `height * 10` instead of `* 15`)
+2. Reduce scale bonus (try `height * 0.05` instead of `* 0.1`)
+
+---
+
+## 📚 FILES MODIFIED
+
+- `src/systems/TerrainSystem.js` - Height generation & visualization
+- `docs/HEIGHT_SYSTEM_PLAN.md` - Implementation plan
+- `docs/2.5D_TERRAIN_GUIDE.md` - This file
+
+---
+
+**Implementation Date:** 2025-12-14  
+**Status:** Phase 1-2 Complete, Phase 3 Optional  
+**Author:** Antigravity AI Assistant