Gym-MiniGrid/gym_minigrid/envs/empty.py

from gym_minigrid.minigrid import Goal, Grid, MiniGridEnv, MissionSpace


class EmptyEnv(MiniGridEnv):
    """
    Empty grid environment, no obstacles, sparse reward
    """

    def __init__(self, size=8, agent_start_pos=(1, 1), agent_start_dir=0, **kwargs):
        self.agent_start_pos = agent_start_pos
        self.agent_start_dir = agent_start_dir

        mission_space = MissionSpace(
            mission_func=lambda: "get to the green goal square"
        )

        super().__init__(
            mission_space=mission_space,
            grid_size=size,
            max_steps=4 * size * size,
            # Set this to True for maximum speed
            see_through_walls=True,
            **kwargs
        )

    def _gen_grid(self, width, height):
        # Create an empty grid
        self.grid = Grid(width, height)

        # Generate the surrounding walls
        self.grid.wall_rect(0, 0, width, height)

        # Place a goal square in the bottom-right corner
        self.put_obj(Goal(), width - 2, height - 2)

        # Place the agent
        if self.agent_start_pos is not None:
            self.agent_pos = self.agent_start_pos
            self.agent_dir = self.agent_start_dir
        else:
            self.place_agent()

        self.mission = "get to the green goal square"