Done! I've built a complete voxel sandbox prototype with all requested features:

## Technical Implementation

### 1. World Architecture
- **Grid System**: 1×1×1 cubes aligned to global grid
- **Perlin Noise**: Implemented with FBM (Fractional Brownian Motion) for varied terrain with hills, valleys, and caves. Math explained in comments:
  - Uses gradient vectors at grid points with smooth interpolation via `6t⁵ - 15t⁴ + 10t³` fade function
  - FBM layers octaves: each has 2× frequency (lacunarity) and 0.5× amplitude (persistence)
  - 3D noise carves caves where threshold > 0.5
- **Chunk Management**: 16×16×16 chunks with face culling - only faces adjacent to air are rendered

### 2. Player Mechanics
- **First-Person Controller**: WASD movement, mouse look, gravity-based jumping
- **Raycasting**: DDA (Digital Differential Analyzer) algorithm stepping through voxel grid:
  - Left click: Destroy targeted block within 5 units
  - Right click: Place selected block on targeted face

### 3. Block Logic & Physics
- **8 Block Types**: Grass, Dirt, Stone, Wood, Leaves, Sand, Water, Cobblestone
- **AABB Collision**: Checks player bounding box against all overlapping solid blocks, resolves each axis separately

### 4. UI & Game Loop
- **Hotbar**: 7 blocks, mouse wheel or number keys to select
- **Dynamic Mesh Update**: Chunks rebuild immediately on block changes, including adjacent chunks at boundaries

**Controls**: WASD move | Space jump | Mouse look | Left click break | Right click place | Scroll/1-7 select block

**Next Ideas:**
1. **Add Trees & Structures** - Procedurally generate trees during terrain creation for a more natural world
2. **Day/Night Cycle** - Animate sun position and sky color, add torches for lighting in caves

**Ready to level up your game? Pick one and let's build it!**