Move Two Across

Action Space	Discrete(7)
Observation Space	Dict('direction': Discrete(4), 'image': Box(0, 255, (7, 7, 3), uint8), 'mission': MissionSpace(<function BabyAIMissionSpace._gen_mission at 0x7f813d9da940>, None))
Reward Range	(0, 1)
Creation	gymnasium.make("BabyAI-MoveTwoAcrossS8N9-v0")

Description

Task of the form: move the A next to the B and the C next to the D. This task is structured to have a very large number of possible instructions.

Mission Space

“put the {color} {type} next to the {color} {type}, then put the {color} {type} next to the {color} {type}”

{color} is the color of the box. Can be “red”, “green”, “blue”, “purple”, “yellow” or “grey”.

{type} is the type of the object. Can be “ball”, “box” or “key”.

Action Space

Num	Name	Action
0	left	Turn left
1	right	Turn right
2	forward	Move forward
3	pickup	Pick up an object
4	drop	Unused
5	toggle	Unused
6	done	Unused

Observation Encoding

• Each tile is encoded as a 3 dimensional tuple: (OBJECT_IDX, COLOR_IDX, STATE)

• OBJECT_TO_IDX and COLOR_TO_IDX mapping can be found in minigrid/core/constants.py

• STATE refers to the door state with 0=open, 1=closed and 2=locked

Rewards

A reward of ‘1 - 0.9 * (step_count / max_steps)’ is given for success, and ‘0’ for failure.

Termination

The episode ends if any one of the following conditions is met:

1. The agent finishes the instruction.

2. Timeout (see max_steps).

Registered Configurations

• BabyAI-MoveTwoAcrossS5N2-v0

• BabyAI-MoveTwoAcrossS8N9-v0