Updates

games/snake/observation.py

@@ -2,9 +2,82 @@ import numpy as np
 from retro.views.headless import HeadlessView
 from retro_gamer.observation import egocentric_board, encode_board, encode_state
 
+HEAD_CHARS = frozenset({">", "<", "^", "v"})
 CHARACTER_SET = ["@", "*", ">", "<", "^", "v"]
+CHARACTER_SET_NORMALIZED = ["@", "*", "H"]
 RADIUS = 8
 
+DIRECTIONS = [(1, 0), (0, -1), (-1, 0), (0, 1)]  # RIGHT, UP, LEFT, DOWN
+RADIUS_WIDE = 8   # 17×17 egocentric window
+RADIUS_NARROW = 3  # 7×7 egocentric window
+
+
+def direction_observation(game):
+    """Normalized 3-char board plus apple_dx, apple_dy, and a one-hot direction.
+
+    Returns board in channel-first (C, H, W) order for the CNN, followed by
+    apple_dx, apple_dy, and 4 one-hot bits encoding the snake's heading.
+    The board collapses all four head characters to 'H', keeping 3 channels
+    instead of 6 while the one-hot direction restores that information cheaply.
+    """
+    view = HeadlessView()
+    view.on_game_start(game)
+    view.render(game)
+    normalized = [
+        ["H" if c in HEAD_CHARS else c for c in row]
+        for row in view.board_characters
+    ]
+    board_vec = encode_board(normalized, CHARACTER_SET_NORMALIZED).transpose(2, 0, 1).flatten()
+    extras = encode_state(game.state, ["apple_dx", "apple_dy"])
+    head = game.get_agent_by_name("Snake head")
+    direction_onehot = np.array(
+        [1.0 if head.direction == d else 0.0 for d in DIRECTIONS],
+        dtype=np.float32,
+    )
+    return np.concatenate([board_vec, extras, direction_onehot])
+
+
+def normalized_observation(game):
+    """Full board with all head chars collapsed to 'H', plus apple_dx and apple_dy.
+
+    Returns board in channel-first (C, H, W) order for the CNN, followed by extras.
+    Character set: ['@' apple, '*' body, 'H' head] — 3 channels instead of 6.
+    """
+    view = HeadlessView()
+    view.on_game_start(game)
+    view.render(game)
+    normalized = [
+        ["H" if c in HEAD_CHARS else c for c in row]
+        for row in view.board_characters
+    ]
+    board_vec = encode_board(normalized, CHARACTER_SET_NORMALIZED).transpose(2, 0, 1).flatten()
+    extras = encode_state(game.state, ["apple_dx", "apple_dy"])
+    return np.concatenate([board_vec, extras])
+
+
+def egocentric_cnn_observation(game):
+    """17×17 egocentric window in channel-first (CHW) format for CNN, plus apple_dx/dy."""
+    view = HeadlessView()
+    view.on_game_start(game)
+    view.render(game)
+    head = game.get_agent_by_name("Snake head")
+    cropped = egocentric_board(view.board_characters, head.position, RADIUS_WIDE)
+    board_vec = encode_board(cropped, CHARACTER_SET).transpose(2, 0, 1).flatten()
+    extras = encode_state(game.state, ["apple_dx", "apple_dy"])
+    return np.concatenate([board_vec, extras])
+
+
+def narrow_egocentric_observation(game):
+    """7×7 egocentric window (flat, for MLP), plus apple_dx and apple_dy."""
+    view = HeadlessView()
+    view.on_game_start(game)
+    view.render(game)
+    head = game.get_agent_by_name("Snake head")
+    cropped = egocentric_board(view.board_characters, head.position, RADIUS_NARROW)
+    board_vec = encode_board(cropped, CHARACTER_SET).flatten()
+    extras = encode_state(game.state, ["apple_dx", "apple_dy"])
+    return np.concatenate([board_vec, extras])
+
 
 def egocentric_observation(game):
     """17×17 window centered on the snake's head, plus apple_dx and apple_dy."""

games/snake/pyproject.toml

@@ -8,3 +8,4 @@ dependencies = ["retro-games>=2.5.0"]
 [tool.retro-gamer]
 actions = ["KEY_RIGHT", "KEY_UP", "KEY_LEFT", "KEY_DOWN"]
 reward = "reward"
+character_set = ["@", "*", "<", ">", "^", "v"]