Initial commit

forager/__init__.py

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+"""Forager: an 8×8 grid game where an agent collects food.
+
+The agent moves in four directions collecting food that respawns on collection.
+The game runs indefinitely; retro-gamer's max_turns_per_episode controls episode length.
+
+Observation features for retro-gamer:
+  food_dx: (food_x - agent_x) / board_width  (positive = food is to the right)
+  food_dy: (food_y - agent_y) / board_height (positive = food is below)
+"""
+
+from random import randint
+from retro.game import Game
+
+BOARD_SIZE = 8
+
+
+class Forager:
+    """The player agent."""
+    name = "Forager"
+    character = '@'
+    color = "green_on_black"
+    position = (0, 0)
+
+    UP = (0, -1)
+    DOWN = (0, 1)
+    LEFT = (-1, 0)
+    RIGHT = (1, 0)
+
+    def __init__(self):
+        self._direction = self.RIGHT
+
+    def handle_keystroke(self, keystroke, game):
+        if keystroke.name == "KEY_RIGHT":
+            self._direction = self.RIGHT
+        elif keystroke.name == "KEY_UP":
+            self._direction = self.UP
+        elif keystroke.name == "KEY_LEFT":
+            self._direction = self.LEFT
+        elif keystroke.name == "KEY_DOWN":
+            self._direction = self.DOWN
+
+    def play_turn(self, game):
+        x, y = self.position
+        dx, dy = self._direction
+        new_pos = (x + dx, y + dy)
+        if game.on_board(new_pos):
+            self.position = new_pos
+
+        game.state['reward'] -= 0.01
+
+        food = game.get_agent_by_name("Food")
+        if self.position == food.position:
+            food.relocate(game)
+            game.state['score'] += 1
+            game.state['reward'] += 1.0
+
+        bw, bh = game.board_size
+        ax, ay = self.position
+        fx, fy = game.get_agent_by_name("Food").position
+        game.state['food_dx'] = (fx - ax) / bw
+        game.state['food_dy'] = (fy - ay) / bh
+
+
+class Food:
+    """The food item. Respawns when collected."""
+    name = "Food"
+    character = '*'
+    color = "yellow_on_black"
+    position = (0, 0)
+
+    def relocate(self, game):
+        bw, bh = game.board_size
+        forager = game.get_agent_by_name("Forager")
+        while True:
+            pos = (randint(0, bw - 1), randint(0, bh - 1))
+            if pos != forager.position:
+                self.position = pos
+                return
+
+
+def create_game():
+    """Return a fresh Forager game."""
+    forager = Forager()
+    food = Food()
+    bw = bh = BOARD_SIZE
+    game = Game(
+        [forager, food],
+        {'score': 0, 'reward': 0.0, 'food_dx': 0.0, 'food_dy': 0.0},
+        board_size=(bw, bh),
+        framerate=12,
+    )
+    forager.position = (randint(0, bw - 1), randint(0, bh - 1))
+    food.relocate(game)
+    bw, bh = game.board_size
+    ax, ay = forager.position
+    fx, fy = food.position
+    game.state['food_dx'] = (fx - ax) / bw
+    game.state['food_dy'] = (fy - ay) / bh
+    return game
+
+
+if __name__ == '__main__':
+    create_game().play()