Convert UIGrid perspective from index to weak_ptr<UIEntity>

Major refactor of the perspective system to use entity references instead of indices:

- Replaced `int perspective` with `std::weak_ptr<UIEntity> perspective_entity`
- Added `bool perspective_enabled` flag for explicit control
- Direct entity assignment: `grid.perspective = player`
- Automatic cleanup when entity is destroyed (weak_ptr becomes invalid)
- No issues with collection reordering or entity removal
- PythonObjectCache integration preserves Python derived classes

API changes:
- Old: `grid.perspective = 0` (index), `-1` for omniscient
- New: `grid.perspective = entity` (object), `None` to clear
- New: `grid.perspective_enabled` controls rendering mode

Three rendering states:
1. `perspective_enabled = False`: Omniscient view (default)
2. `perspective_enabled = True` with valid entity: Entity's FOV
3. `perspective_enabled = True` with invalid entity: All black

Also includes:
- Part 3: Procedural dungeon generation with libtcod.line()
- Part 4: Field of view with entity perspective switching

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

roguelike_tutorial/part_3.py

@@ -0,0 +1,299 @@
+"""
+McRogueFace Tutorial - Part 3: Procedural Dungeon Generation
+
+This tutorial builds on Part 2 by adding:
+- Binary Space Partition (BSP) dungeon generation
+- Rooms connected by hallways using libtcod.line()
+- Walkable/non-walkable terrain
+- Player spawning in a valid location
+- Wall tiles that block movement
+
+Key code references:
+- src/scripts/cos_level.py (lines 7-15, 184-217, 218-224) - BSP algorithm
+- mcrfpy.libtcod.line() for smooth hallway generation
+"""
+import mcrfpy
+import random
+
+# Create and activate a new scene
+mcrfpy.createScene("tutorial")
+mcrfpy.setScene("tutorial")
+
+# Load the texture (4x3 tiles, 64x48 pixels total, 16x16 per tile)
+texture = mcrfpy.Texture("assets/tutorial2.png", 16, 16)
+
+# Load the hero sprite texture
+hero_texture = mcrfpy.Texture("assets/custom_player.png", 16, 16)
+
+# Create a grid of tiles
+grid_width, grid_height = 40, 30  # Larger grid for dungeon
+
+# Calculate the size in pixels to fit the entire grid on-screen
+zoom = 2.0
+grid_size = grid_width * zoom * 16, grid_height * zoom * 16
+
+# Calculate the position to center the grid on the screen
+grid_position = (1024 - grid_size[0]) / 2, (768 - grid_size[1]) / 2
+
+# Create the grid with a TCODMap for pathfinding/FOV
+grid = mcrfpy.Grid(
+    pos=grid_position,
+    grid_size=(grid_width, grid_height),
+    texture=texture,
+    size=grid_size,
+)
+
+grid.zoom = zoom
+
+# Define tile types
+FLOOR_TILES = [0, 1, 2, 4, 5, 6, 8, 9, 10]
+WALL_TILES = [3, 7, 11]
+
+# Room class for BSP
+class Room:
+    def __init__(self, x, y, w, h):
+        self.x1 = x
+        self.y1 = y
+        self.x2 = x + w
+        self.y2 = y + h
+        self.w = w
+        self.h = h
+    
+    def center(self):
+        """Return the center coordinates of the room"""
+        center_x = (self.x1 + self.x2) // 2
+        center_y = (self.y1 + self.y2) // 2
+        return (center_x, center_y)
+    
+    def intersects(self, other):
+        """Return True if this room overlaps with another"""
+        return (self.x1 <= other.x2 and self.x2 >= other.x1 and
+                self.y1 <= other.y2 and self.y2 >= other.y1)
+
+# Dungeon generation functions
+def carve_room(room):
+    """Carve out a room in the grid - referenced from cos_level.py lines 117-120"""
+    # Using individual updates for now (batch updates would be more efficient)
+    for x in range(room.x1, room.x2):
+        for y in range(room.y1, room.y2):
+            if 0 <= x < grid_width and 0 <= y < grid_height:
+                point = grid.at(x, y)
+                if point:
+                    point.tilesprite = random.choice(FLOOR_TILES)
+                    point.walkable = True
+                    point.transparent = True
+
+def carve_hallway(x1, y1, x2, y2):
+    """Carve a hallway between two points using libtcod.line()
+    Referenced from cos_level.py lines 184-217, improved with libtcod.line()
+    """
+    # Get all points along the line
+    points = mcrfpy.libtcod.line(x1, y1, x2, y2)
+    
+    # Carve out each point
+    for x, y in points:
+        if 0 <= x < grid_width and 0 <= y < grid_height:
+            point = grid.at(x, y)
+            if point:
+                point.tilesprite = random.choice(FLOOR_TILES)
+                point.walkable = True
+                point.transparent = True
+
+def generate_dungeon(max_rooms=10, room_min_size=4, room_max_size=10):
+    """Generate a dungeon using simplified BSP approach
+    Referenced from cos_level.py lines 218-224
+    """
+    rooms = []
+    
+    # First, fill everything with walls
+    for y in range(grid_height):
+        for x in range(grid_width):
+            point = grid.at(x, y)
+            if point:
+                point.tilesprite = random.choice(WALL_TILES)
+                point.walkable = False
+                point.transparent = False
+    
+    # Generate rooms
+    for _ in range(max_rooms):
+        # Random room size
+        w = random.randint(room_min_size, room_max_size)
+        h = random.randint(room_min_size, room_max_size)
+        
+        # Random position (with margin from edges)
+        x = random.randint(1, grid_width - w - 1)
+        y = random.randint(1, grid_height - h - 1)
+        
+        new_room = Room(x, y, w, h)
+        
+        # Check if it overlaps with existing rooms
+        failed = False
+        for other_room in rooms:
+            if new_room.intersects(other_room):
+                failed = True
+                break
+        
+        if not failed:
+            # Carve out the room
+            carve_room(new_room)
+            
+            # If not the first room, connect to previous room
+            if rooms:
+                # Get centers
+                prev_x, prev_y = rooms[-1].center()
+                new_x, new_y = new_room.center()
+                
+                # Carve hallway using libtcod.line()
+                carve_hallway(prev_x, prev_y, new_x, new_y)
+            
+            rooms.append(new_room)
+    
+    return rooms
+
+# Generate the dungeon
+rooms = generate_dungeon(max_rooms=8, room_min_size=4, room_max_size=8)
+
+# Add the grid to the scene
+mcrfpy.sceneUI("tutorial").append(grid)
+
+# Spawn player in the first room
+if rooms:
+    spawn_x, spawn_y = rooms[0].center()
+else:
+    # Fallback spawn position
+    spawn_x, spawn_y = 4, 4
+
+# Create a player entity at the spawn position
+player = mcrfpy.Entity(
+    (spawn_x, spawn_y),
+    texture=hero_texture,
+    sprite_index=0
+)
+
+# Add the player entity to the grid
+grid.entities.append(player)
+grid.center = (player.x + 0.5) * 16, (player.y + 0.5) * 16
+
+# Movement state tracking (from Part 2)
+is_moving = False
+move_queue = []
+current_destination = None
+current_move = None
+
+# Store animation references
+player_anim_x = None
+player_anim_y = None
+grid_anim_x = None
+grid_anim_y = None
+
+def movement_complete(anim, target):
+    """Called when movement animation completes"""
+    global is_moving, move_queue, current_destination, current_move
+    global player_anim_x, player_anim_y
+    
+    is_moving = False
+    current_move = None
+    current_destination = None
+    player_anim_x = None
+    player_anim_y = None
+    
+    grid.center = (player.x + 0.5) * 16, (player.y + 0.5) * 16
+    
+    if move_queue:
+        next_move = move_queue.pop(0)
+        process_move(next_move)
+
+motion_speed = 0.20  # Slightly faster for dungeon exploration
+
+def can_move_to(x, y):
+    """Check if a position is valid for movement"""
+    # Boundary check
+    if x < 0 or x >= grid_width or y < 0 or y >= grid_height:
+        return False
+    
+    # Walkability check
+    point = grid.at(x, y)
+    if point and point.walkable:
+        return True
+    return False
+
+def process_move(key):
+    """Process a move based on the key"""
+    global is_moving, current_move, current_destination, move_queue
+    global player_anim_x, player_anim_y, grid_anim_x, grid_anim_y
+    
+    if is_moving:
+        move_queue.clear()
+        move_queue.append(key)
+        return
+    
+    px, py = int(player.x), int(player.y)
+    new_x, new_y = px, py
+    
+    if key == "W" or key == "Up":
+        new_y -= 1
+    elif key == "S" or key == "Down":
+        new_y += 1
+    elif key == "A" or key == "Left":
+        new_x -= 1
+    elif key == "D" or key == "Right":
+        new_x += 1
+    
+    # Check if we can move to the new position
+    if new_x != px or new_y != py:
+        if can_move_to(new_x, new_y):
+            is_moving = True
+            current_move = key
+            current_destination = (new_x, new_y)
+            
+            if new_x != px:
+                player_anim_x = mcrfpy.Animation("x", float(new_x), motion_speed, "easeInOutQuad", callback=movement_complete)
+                player_anim_x.start(player)
+            elif new_y != py:
+                player_anim_y = mcrfpy.Animation("y", float(new_y), motion_speed, "easeInOutQuad", callback=movement_complete)
+                player_anim_y.start(player)
+            
+            grid_anim_x = mcrfpy.Animation("center_x", (new_x + 0.5) * 16, motion_speed, "linear")
+            grid_anim_y = mcrfpy.Animation("center_y", (new_y + 0.5) * 16, motion_speed, "linear")
+            grid_anim_x.start(grid)
+            grid_anim_y.start(grid)
+        else:
+            # Play a "bump" sound or visual feedback here
+            print(f"Can't move to ({new_x}, {new_y}) - blocked!")
+
+def handle_keys(key, state):
+    """Handle keyboard input to move the player"""
+    if state == "start":
+        if key in ["W", "Up", "S", "Down", "A", "Left", "D", "Right"]:
+            process_move(key)
+
+# Register the keyboard handler
+mcrfpy.keypressScene(handle_keys)
+
+# Add UI elements
+title = mcrfpy.Caption((320, 10),
+    text="McRogueFace Tutorial - Part 3: Dungeon Generation",
+)
+title.fill_color = mcrfpy.Color(255, 255, 255, 255)
+mcrfpy.sceneUI("tutorial").append(title)
+
+instructions = mcrfpy.Caption((150, 750),
+    text=f"Procedural dungeon with {len(rooms)} rooms connected by hallways!",
+)
+instructions.font_size = 18
+instructions.fill_color = mcrfpy.Color(200, 200, 200, 255)
+mcrfpy.sceneUI("tutorial").append(instructions)
+
+# Debug info
+debug_caption = mcrfpy.Caption((10, 40),
+    text=f"Grid: {grid_width}x{grid_height} | Player spawned at ({spawn_x}, {spawn_y})",
+)
+debug_caption.font_size = 16
+debug_caption.fill_color = mcrfpy.Color(255, 255, 0, 255)
+mcrfpy.sceneUI("tutorial").append(debug_caption)
+
+print("Tutorial Part 3 loaded!")
+print(f"Generated dungeon with {len(rooms)} rooms")
+print(f"Player spawned at ({spawn_x}, {spawn_y})")
+print("Walls now block movement!")
+print("Use WASD or Arrow keys to explore the dungeon!")

roguelike_tutorial/part_4.py

@@ -0,0 +1,355 @@
+"""
+McRogueFace Tutorial - Part 4: Field of View
+
+This tutorial builds on Part 3 by adding:
+- Field of view calculation using grid.compute_fov()
+- Entity perspective rendering with grid.perspective
+- Three visibility states: unexplored (black), explored (dark), visible (lit)
+- Memory of previously seen areas
+- Enemy entity to demonstrate perspective switching
+
+Key code references:
+- tests/unit/test_tcod_fov_entities.py (lines 89-118) - FOV with multiple entities
+- ROADMAP.md (lines 216-229) - FOV system implementation details
+"""
+import mcrfpy
+import random
+
+# Create and activate a new scene
+mcrfpy.createScene("tutorial")
+mcrfpy.setScene("tutorial")
+
+# Load the texture (4x3 tiles, 64x48 pixels total, 16x16 per tile)
+texture = mcrfpy.Texture("assets/tutorial2.png", 16, 16)
+
+# Load the hero sprite texture
+hero_texture = mcrfpy.Texture("assets/custom_player.png", 16, 16)
+
+# Create a grid of tiles
+grid_width, grid_height = 40, 30
+
+# Calculate the size in pixels
+zoom = 2.0
+grid_size = grid_width * zoom * 16, grid_height * zoom * 16
+
+# Calculate the position to center the grid on the screen
+grid_position = (1024 - grid_size[0]) / 2, (768 - grid_size[1]) / 2
+
+# Create the grid with a TCODMap for pathfinding/FOV
+grid = mcrfpy.Grid(
+    pos=grid_position,
+    grid_size=(grid_width, grid_height),
+    texture=texture,
+    size=grid_size,
+)
+
+grid.zoom = zoom
+
+# Define tile types
+FLOOR_TILES = [0, 1, 2, 4, 5, 6, 8, 9, 10]
+WALL_TILES = [3, 7, 11]
+
+# Room class for BSP
+class Room:
+    def __init__(self, x, y, w, h):
+        self.x1 = x
+        self.y1 = y
+        self.x2 = x + w
+        self.y2 = y + h
+        self.w = w
+        self.h = h
+    
+    def center(self):
+        center_x = (self.x1 + self.x2) // 2
+        center_y = (self.y1 + self.y2) // 2
+        return (center_x, center_y)
+    
+    def intersects(self, other):
+        return (self.x1 <= other.x2 and self.x2 >= other.x1 and
+                self.y1 <= other.y2 and self.y2 >= other.y1)
+
+# Dungeon generation functions (from Part 3)
+def carve_room(room):
+    for x in range(room.x1, room.x2):
+        for y in range(room.y1, room.y2):
+            if 0 <= x < grid_width and 0 <= y < grid_height:
+                point = grid.at(x, y)
+                if point:
+                    point.tilesprite = random.choice(FLOOR_TILES)
+                    point.walkable = True
+                    point.transparent = True
+
+def carve_hallway(x1, y1, x2, y2):
+    points = mcrfpy.libtcod.line(x1, y1, x2, y2)
+    
+    for x, y in points:
+        if 0 <= x < grid_width and 0 <= y < grid_height:
+            point = grid.at(x, y)
+            if point:
+                point.tilesprite = random.choice(FLOOR_TILES)
+                point.walkable = True
+                point.transparent = True
+
+def generate_dungeon(max_rooms=10, room_min_size=4, room_max_size=10):
+    rooms = []
+    
+    # Fill with walls
+    for y in range(grid_height):
+        for x in range(grid_width):
+            point = grid.at(x, y)
+            if point:
+                point.tilesprite = random.choice(WALL_TILES)
+                point.walkable = False
+                point.transparent = False
+    
+    # Generate rooms
+    for _ in range(max_rooms):
+        w = random.randint(room_min_size, room_max_size)
+        h = random.randint(room_min_size, room_max_size)
+        x = random.randint(1, grid_width - w - 1)
+        y = random.randint(1, grid_height - h - 1)
+        
+        new_room = Room(x, y, w, h)
+        
+        failed = False
+        for other_room in rooms:
+            if new_room.intersects(other_room):
+                failed = True
+                break
+        
+        if not failed:
+            carve_room(new_room)
+            
+            if rooms:
+                prev_x, prev_y = rooms[-1].center()
+                new_x, new_y = new_room.center()
+                carve_hallway(prev_x, prev_y, new_x, new_y)
+            
+            rooms.append(new_room)
+    
+    return rooms
+
+# Generate the dungeon
+rooms = generate_dungeon(max_rooms=8, room_min_size=4, room_max_size=8)
+
+# Add the grid to the scene
+mcrfpy.sceneUI("tutorial").append(grid)
+
+# Spawn player in the first room
+if rooms:
+    spawn_x, spawn_y = rooms[0].center()
+else:
+    spawn_x, spawn_y = 4, 4
+
+# Create a player entity
+player = mcrfpy.Entity(
+    (spawn_x, spawn_y),
+    texture=hero_texture,
+    sprite_index=0
+)
+
+# Add the player entity to the grid
+grid.entities.append(player)
+
+# Create an enemy entity in another room (to demonstrate perspective switching)
+enemy = None
+if len(rooms) > 1:
+    enemy_x, enemy_y = rooms[1].center()
+    enemy = mcrfpy.Entity(
+        (enemy_x, enemy_y),
+        texture=texture,
+        sprite_index=117  # Enemy sprite
+    )
+    grid.entities.append(enemy)
+
+# Set the grid perspective to the player by default
+# Note: The new perspective system uses entity references directly
+grid.perspective = player
+
+# Initial FOV computation
+def update_fov():
+    """Update field of view from current perspective
+    Referenced from test_tcod_fov_entities.py lines 89-118
+    """
+    if grid.perspective == player:
+        grid.compute_fov(int(player.x), int(player.y), radius=8, algorithm=0)
+    elif enemy and grid.perspective == enemy:
+        grid.compute_fov(int(enemy.x), int(enemy.y), radius=6, algorithm=0)
+
+# Perform initial FOV calculation
+update_fov()
+
+# Center grid on current perspective
+def center_on_perspective():
+    if grid.perspective == player:
+        grid.center = (player.x + 0.5) * 16, (player.y + 0.5) * 16
+    elif enemy and grid.perspective == enemy:
+        grid.center = (enemy.x + 0.5) * 16, (enemy.y + 0.5) * 16
+
+center_on_perspective()
+
+# Movement state tracking (from Part 3)
+is_moving = False
+move_queue = []
+current_destination = None
+current_move = None
+
+# Store animation references
+player_anim_x = None
+player_anim_y = None
+grid_anim_x = None
+grid_anim_y = None
+
+def movement_complete(anim, target):
+    """Called when movement animation completes"""
+    global is_moving, move_queue, current_destination, current_move
+    global player_anim_x, player_anim_y
+    
+    is_moving = False
+    current_move = None
+    current_destination = None
+    player_anim_x = None
+    player_anim_y = None
+    
+    # Update FOV after movement
+    update_fov()
+    center_on_perspective()
+    
+    if move_queue:
+        next_move = move_queue.pop(0)
+        process_move(next_move)
+
+motion_speed = 0.20
+
+def can_move_to(x, y):
+    """Check if a position is valid for movement"""
+    if x < 0 or x >= grid_width or y < 0 or y >= grid_height:
+        return False
+    
+    point = grid.at(x, y)
+    if point and point.walkable:
+        return True
+    return False
+
+def process_move(key):
+    """Process a move based on the key"""
+    global is_moving, current_move, current_destination, move_queue
+    global player_anim_x, player_anim_y, grid_anim_x, grid_anim_y
+    
+    # Only allow player movement when in player perspective
+    if grid.perspective != player:
+        return
+    
+    if is_moving:
+        move_queue.clear()
+        move_queue.append(key)
+        return
+    
+    px, py = int(player.x), int(player.y)
+    new_x, new_y = px, py
+    
+    if key == "W" or key == "Up":
+        new_y -= 1
+    elif key == "S" or key == "Down":
+        new_y += 1
+    elif key == "A" or key == "Left":
+        new_x -= 1
+    elif key == "D" or key == "Right":
+        new_x += 1
+    
+    if new_x != px or new_y != py:
+        if can_move_to(new_x, new_y):
+            is_moving = True
+            current_move = key
+            current_destination = (new_x, new_y)
+            
+            if new_x != px:
+                player_anim_x = mcrfpy.Animation("x", float(new_x), motion_speed, "easeInOutQuad", callback=movement_complete)
+                player_anim_x.start(player)
+            elif new_y != py:
+                player_anim_y = mcrfpy.Animation("y", float(new_y), motion_speed, "easeInOutQuad", callback=movement_complete)
+                player_anim_y.start(player)
+            
+            grid_anim_x = mcrfpy.Animation("center_x", (new_x + 0.5) * 16, motion_speed, "linear")
+            grid_anim_y = mcrfpy.Animation("center_y", (new_y + 0.5) * 16, motion_speed, "linear")
+            grid_anim_x.start(grid)
+            grid_anim_y.start(grid)
+
+def handle_keys(key, state):
+    """Handle keyboard input"""
+    if state == "start":
+        # Movement keys
+        if key in ["W", "Up", "S", "Down", "A", "Left", "D", "Right"]:
+            process_move(key)
+        
+        # Perspective switching
+        elif key == "Tab":
+            # Switch perspective between player and enemy
+            if enemy:
+                if grid.perspective == player:
+                    grid.perspective = enemy
+                    print("Switched to enemy perspective")
+                else:
+                    grid.perspective = player
+                    print("Switched to player perspective")
+                
+                # Update FOV and camera for new perspective
+                update_fov()
+                center_on_perspective()
+
+# Register the keyboard handler
+mcrfpy.keypressScene(handle_keys)
+
+# Add UI elements
+title = mcrfpy.Caption((320, 10),
+    text="McRogueFace Tutorial - Part 4: Field of View",
+)
+title.fill_color = mcrfpy.Color(255, 255, 255, 255)
+mcrfpy.sceneUI("tutorial").append(title)
+
+instructions = mcrfpy.Caption((150, 720),
+    text="Use WASD/Arrows to move. Press Tab to switch perspective!",
+)
+instructions.font_size = 18
+instructions.fill_color = mcrfpy.Color(200, 200, 200, 255)
+mcrfpy.sceneUI("tutorial").append(instructions)
+
+# FOV info
+fov_caption = mcrfpy.Caption((150, 745),
+    text="FOV: Player (radius 8) | Enemy visible in other room",
+)
+fov_caption.font_size = 16
+fov_caption.fill_color = mcrfpy.Color(100, 200, 255, 255)
+mcrfpy.sceneUI("tutorial").append(fov_caption)
+
+# Debug info
+debug_caption = mcrfpy.Caption((10, 40),
+    text=f"Grid: {grid_width}x{grid_height} | Rooms: {len(rooms)} | Perspective: Player",
+)
+debug_caption.font_size = 16
+debug_caption.fill_color = mcrfpy.Color(255, 255, 0, 255)
+mcrfpy.sceneUI("tutorial").append(debug_caption)
+
+# Update function for perspective display
+def update_perspective_display():
+    current_perspective = "Player" if grid.perspective == player else "Enemy"
+    debug_caption.text = f"Grid: {grid_width}x{grid_height} | Rooms: {len(rooms)} | Perspective: {current_perspective}"
+    
+    if grid.perspective == player:
+        fov_caption.text = "FOV: Player (radius 8) | Tab to switch perspective"
+    else:
+        fov_caption.text = "FOV: Enemy (radius 6) | Tab to switch perspective"
+
+# Timer to update display
+def update_display(runtime):
+    update_perspective_display()
+
+mcrfpy.setTimer("display_update", update_display, 100)
+
+print("Tutorial Part 4 loaded!")
+print("Field of View system active!")
+print("- Unexplored areas are black")
+print("- Previously seen areas are dark") 
+print("- Currently visible areas are lit")
+print("Press Tab to switch between player and enemy perspective!")
+print("Use WASD or Arrow keys to move!")

src/UIGrid.cpp

@@ -2,13 +2,14 @@
 #include "GameEngine.h"
 #include "McRFPy_API.h"
 #include "PythonObjectCache.h"
+#include "UIEntity.h"
 #include <algorithm>
 // UIDrawable methods now in UIBase.h
 
 UIGrid::UIGrid() 
 : grid_x(0), grid_y(0), zoom(1.0f), center_x(0.0f), center_y(0.0f), ptex(nullptr),
   fill_color(8, 8, 8, 255), tcod_map(nullptr), tcod_dijkstra(nullptr), tcod_path(nullptr),
-  perspective(-1)  // Default to omniscient view
+  perspective_enabled(false)  // Default to omniscient view
 {
     // Initialize entities list
     entities = std::make_shared<std::list<std::shared_ptr<UIEntity>>>();
@@ -36,7 +37,7 @@ UIGrid::UIGrid(int gx, int gy, std::shared_ptr<PyTexture> _ptex, sf::Vector2f _x
   zoom(1.0f), 
   ptex(_ptex), points(gx * gy),
   fill_color(8, 8, 8, 255), tcod_map(nullptr), tcod_dijkstra(nullptr), tcod_path(nullptr),
-  perspective(-1)  // Default to omniscient view
+  perspective_enabled(false)  // Default to omniscient view
 {
     // Use texture dimensions if available, otherwise use defaults
     int cell_width = _ptex ? _ptex->sprite_width : DEFAULT_CELL_WIDTH;
@@ -189,54 +190,78 @@ void UIGrid::render(sf::Vector2f offset, sf::RenderTarget& target)
     
 
     // top layer - opacity for discovered / visible status based on perspective
-    // Only render visibility overlay if perspective is set (not omniscient)
-    if (perspective >= 0 && perspective < static_cast<int>(entities->size())) {
-        // Get the entity whose perspective we're using
-        auto it = entities->begin();
-        std::advance(it, perspective);
-        auto& entity = *it;
+    // Only render visibility overlay if perspective is enabled
+    if (perspective_enabled) {
+        auto entity = perspective_entity.lock();
         
         // Create rectangle for overlays
         sf::RectangleShape overlay;
         overlay.setSize(sf::Vector2f(cell_width * zoom, cell_height * zoom));
         
-        for (int x = (left_edge - 1 >= 0 ? left_edge - 1 : 0);
-            x < x_limit;
-            x+=1)
-        {
-            for (int y = (top_edge - 1 >= 0 ? top_edge - 1 : 0);
-                y < y_limit;
-                y+=1)
+        if (entity) {
+            // Valid entity - use its gridstate for visibility
+            for (int x = (left_edge - 1 >= 0 ? left_edge - 1 : 0);
+                x < x_limit;
+                x+=1)
             {
-                // Skip out-of-bounds cells
-                if (x < 0 || x >= grid_x || y < 0 || y >= grid_y) continue;
-                
-                auto pixel_pos = sf::Vector2f(
-                        (x*cell_width - left_spritepixels) * zoom,
-                        (y*cell_height - top_spritepixels) * zoom );
+                for (int y = (top_edge - 1 >= 0 ? top_edge - 1 : 0);
+                    y < y_limit;
+                    y+=1)
+                {
+                    // Skip out-of-bounds cells
+                    if (x < 0 || x >= grid_x || y < 0 || y >= grid_y) continue;
+                    
+                    auto pixel_pos = sf::Vector2f(
+                            (x*cell_width - left_spritepixels) * zoom,
+                            (y*cell_height - top_spritepixels) * zoom );
 
-                // Get visibility state from entity's perspective
-                int idx = y * grid_x + x;
-                if (idx >= 0 && idx < static_cast<int>(entity->gridstate.size())) {
-                    const auto& state = entity->gridstate[idx];
+                    // Get visibility state from entity's perspective
+                    int idx = y * grid_x + x;
+                    if (idx >= 0 && idx < static_cast<int>(entity->gridstate.size())) {
+                        const auto& state = entity->gridstate[idx];
+                        
+                        overlay.setPosition(pixel_pos);
+                        
+                        // Three overlay colors as specified:
+                        if (!state.discovered) {
+                            // Never seen - black
+                            overlay.setFillColor(sf::Color(0, 0, 0, 255));
+                            renderTexture.draw(overlay);
+                        } else if (!state.visible) {
+                            // Discovered but not currently visible - dark gray
+                            overlay.setFillColor(sf::Color(32, 32, 40, 192));
+                            renderTexture.draw(overlay);
+                        }
+                        // If visible and discovered, no overlay (fully visible)
+                    }
+                }
+            }
+        } else {
+            // Invalid/destroyed entity with perspective_enabled = true
+            // Show all cells as undiscovered (black)
+            for (int x = (left_edge - 1 >= 0 ? left_edge - 1 : 0);
+                x < x_limit;
+                x+=1)
+            {
+                for (int y = (top_edge - 1 >= 0 ? top_edge - 1 : 0);
+                    y < y_limit;
+                    y+=1)
+                {
+                    // Skip out-of-bounds cells
+                    if (x < 0 || x >= grid_x || y < 0 || y >= grid_y) continue;
+                    
+                    auto pixel_pos = sf::Vector2f(
+                            (x*cell_width - left_spritepixels) * zoom,
+                            (y*cell_height - top_spritepixels) * zoom );
                     
                     overlay.setPosition(pixel_pos);
-                    
-                    // Three overlay colors as specified:
-                    if (!state.discovered) {
-                        // Never seen - black
-                        overlay.setFillColor(sf::Color(0, 0, 0, 255));
-                        renderTexture.draw(overlay);
-                    } else if (!state.visible) {
-                        // Discovered but not currently visible - dark gray
-                        overlay.setFillColor(sf::Color(32, 32, 40, 192));
-                        renderTexture.draw(overlay);
-                    }
-                    // If visible and discovered, no overlay (fully visible)
+                    overlay.setFillColor(sf::Color(0, 0, 0, 255));
+                    renderTexture.draw(overlay);
                 }
             }
         }
     }
+    // else: omniscient view (no overlays)
 
     // grid lines for testing & validation
     /*
@@ -527,7 +552,7 @@ int UIGrid::init(PyUIGridObject* self, PyObject* args, PyObject* kwds) {
     PyObject* click_handler = nullptr;
     float center_x = 0.0f, center_y = 0.0f;
     float zoom = 1.0f;
-    int perspective = -1; // perspective is a difficult __init__ arg; needs an entity in collection to work
+    // perspective is now handled via properties, not init args
     int visible = 1;
     float opacity = 1.0f;
     int z_index = 0;
@@ -539,15 +564,15 @@ int UIGrid::init(PyUIGridObject* self, PyObject* args, PyObject* kwds) {
     static const char* kwlist[] = {
         "pos", "size", "grid_size", "texture",  // Positional args (as per spec)
         // Keyword-only args
-        "fill_color", "click", "center_x", "center_y", "zoom", "perspective",
+        "fill_color", "click", "center_x", "center_y", "zoom",
         "visible", "opacity", "z_index", "name", "x", "y", "w", "h", "grid_x", "grid_y",
         nullptr
     };
     
     // Parse arguments with | for optional positional args
-    if (!PyArg_ParseTupleAndKeywords(args, kwds, "|OOOOOOfffiifizffffii", const_cast<char**>(kwlist),
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "|OOOOOOfffifizffffii", const_cast<char**>(kwlist),
                                      &pos_obj, &size_obj, &grid_size_obj, &textureObj,  // Positional
-                                     &fill_color, &click_handler, &center_x, &center_y, &zoom, &perspective,
+                                     &fill_color, &click_handler, &center_x, &center_y, &zoom,
                                      &visible, &opacity, &z_index, &name, &x, &y, &w, &h, &grid_x, &grid_y)) {
         return -1;
     }
@@ -653,7 +678,8 @@ int UIGrid::init(PyUIGridObject* self, PyObject* args, PyObject* kwds) {
     self->data->center_x = center_x;
     self->data->center_y = center_y;
     self->data->zoom = zoom;
-    self->data->perspective = perspective;
+    // perspective is now handled by perspective_entity and perspective_enabled
+    // self->data->perspective = perspective;
     self->data->visible = visible;
     self->data->opacity = opacity;
     self->data->z_index = z_index;
@@ -941,33 +967,77 @@ int UIGrid::set_fill_color(PyUIGridObject* self, PyObject* value, void* closure)
 
 PyObject* UIGrid::get_perspective(PyUIGridObject* self, void* closure)
 {
-    return PyLong_FromLong(self->data->perspective);
+    auto locked = self->data->perspective_entity.lock();
+    if (locked) {
+        // Check cache first to preserve derived class
+        if (locked->serial_number != 0) {
+            PyObject* cached = PythonObjectCache::getInstance().lookup(locked->serial_number);
+            if (cached) {
+                return cached;  // Already INCREF'd by lookup
+            }
+        }
+        
+        // Legacy: If the entity has a stored Python object reference
+        if (locked->self != nullptr) {
+            Py_INCREF(locked->self);
+            return locked->self;
+        }
+        
+        // Otherwise, create a new base Entity object
+        auto type = (PyTypeObject*)PyObject_GetAttrString(McRFPy_API::mcrf_module, "Entity");
+        auto o = (PyUIEntityObject*)type->tp_alloc(type, 0);
+        if (o) {
+            o->data = locked;
+            o->weakreflist = NULL;
+            Py_DECREF(type);
+            return (PyObject*)o;
+        }
+        Py_XDECREF(type);
+    }
+    Py_RETURN_NONE;
 }
 
 int UIGrid::set_perspective(PyUIGridObject* self, PyObject* value, void* closure)
 {
-    long perspective = PyLong_AsLong(value);
-    if (PyErr_Occurred()) {
+    if (value == Py_None) {
+        // Clear perspective but keep perspective_enabled unchanged
+        self->data->perspective_entity.reset();
+        return 0;
+    }
+    
+    // Extract UIEntity from PyObject
+    // Get the Entity type from the module
+    auto entity_type = PyObject_GetAttrString(McRFPy_API::mcrf_module, "Entity");
+    if (!entity_type) {
+        PyErr_SetString(PyExc_RuntimeError, "Could not get Entity type from mcrfpy module");
         return -1;
     }
     
-    // Validate perspective (-1 for omniscient, or valid entity index)
-    if (perspective < -1) {
-        PyErr_SetString(PyExc_ValueError, "perspective must be -1 (omniscient) or a valid entity index");
+    if (!PyObject_IsInstance(value, entity_type)) {
+        Py_DECREF(entity_type);
+        PyErr_SetString(PyExc_TypeError, "perspective must be a UIEntity or None");
         return -1;
     }
+    Py_DECREF(entity_type);
     
-    // Check if entity index is valid (if not omniscient)
-    if (perspective >= 0 && self->data->entities) {
-        int entity_count = self->data->entities->size();
-        if (perspective >= entity_count) {
-            PyErr_Format(PyExc_IndexError, "perspective index %ld out of range (grid has %d entities)", 
-                         perspective, entity_count);
-            return -1;
-        }
+    PyUIEntityObject* entity_obj = (PyUIEntityObject*)value;
+    self->data->perspective_entity = entity_obj->data;
+    self->data->perspective_enabled = true;  // Enable perspective when entity assigned
+    return 0;
+}
+
+PyObject* UIGrid::get_perspective_enabled(PyUIGridObject* self, void* closure)
+{
+    return PyBool_FromLong(self->data->perspective_enabled);
+}
+
+int UIGrid::set_perspective_enabled(PyUIGridObject* self, PyObject* value, void* closure)
+{
+    int enabled = PyObject_IsTrue(value);
+    if (enabled == -1) {
+        return -1;  // Error occurred
     }
-    
-    self->data->perspective = perspective;
+    self->data->perspective_enabled = enabled;
     return 0;
 }
 
@@ -1285,9 +1355,11 @@ PyGetSetDef UIGrid::getsetters[] = {
     {"texture", (getter)UIGrid::get_texture, NULL, "Texture of the grid", NULL}, //TODO 7DRL-day2-item5
     {"fill_color", (getter)UIGrid::get_fill_color, (setter)UIGrid::set_fill_color, "Background fill color of the grid", NULL},
     {"perspective", (getter)UIGrid::get_perspective, (setter)UIGrid::set_perspective, 
-     "Entity perspective index for FOV rendering (-1 for omniscient view, 0+ for entity index). "
-     "When set to an entity index, only cells visible to that entity are rendered normally; "
-     "explored but not visible cells are darkened, and unexplored cells are black.", NULL},
+     "Entity whose perspective to use for FOV rendering (None for omniscient view). "
+     "Setting an entity automatically enables perspective mode.", NULL},
+    {"perspective_enabled", (getter)UIGrid::get_perspective_enabled, (setter)UIGrid::set_perspective_enabled,
+     "Whether to use perspective-based FOV rendering. When True with no valid entity, "
+     "all cells appear undiscovered.", NULL},
     {"z_index", (getter)UIDrawable::get_int, (setter)UIDrawable::set_int, "Z-order for rendering (lower values rendered first)", (void*)PyObjectsEnum::UIGRID},
     {"name", (getter)UIDrawable::get_name, (setter)UIDrawable::set_name, "Name for finding elements", (void*)PyObjectsEnum::UIGRID},
     UIDRAWABLE_GETSETTERS,

src/UIGrid.h

@@ -77,8 +77,9 @@ public:
     // Background rendering
     sf::Color fill_color;
     
-    // Perspective system - which entity's view to render (-1 = omniscient/default)
-    int perspective;
+    // Perspective system - entity whose view to render
+    std::weak_ptr<UIEntity> perspective_entity;  // Weak reference to perspective entity
+    bool perspective_enabled;                     // Whether to use perspective rendering
     
     // Property system for animations
     bool setProperty(const std::string& name, float value) override;
@@ -103,6 +104,8 @@ public:
     static int set_fill_color(PyUIGridObject* self, PyObject* value, void* closure);
     static PyObject* get_perspective(PyUIGridObject* self, void* closure);
     static int set_perspective(PyUIGridObject* self, PyObject* value, void* closure);
+    static PyObject* get_perspective_enabled(PyUIGridObject* self, void* closure);
+    static int set_perspective_enabled(PyUIGridObject* self, PyObject* value, void* closure);
     static PyObject* py_at(PyUIGridObject* self, PyObject* args, PyObject* kwds);
     static PyObject* py_compute_fov(PyUIGridObject* self, PyObject* args, PyObject* kwds);
     static PyObject* py_is_in_fov(PyUIGridObject* self, PyObject* args);