Amidar

This environment is part of the Atari environments. Please read that page first for general information.

Action Space	Discrete(10)
Observation Space	Box(0, 255, (210, 160, 3), uint8)
Import	gymnasium.make("ALE/Amidar-v5")

For more Amidar variants with different observation and action spaces, see the variants section.

Description

This game is similar to Pac-Man: You are trying to visit all places on a 2-dimensional grid while simultaneously avoiding your enemies. You can turn the tables at one point in the game: Your enemies turn into chickens and you can catch them.

For a more detailed documentation, see the AtariAge page

Actions

Amidar has the action space of Discrete(10) with the table below listing the meaning of each action’s meanings. To enable all 18 possible actions that can be performed on an Atari 2600, specify full_action_space=True during initialization or by passing full_action_space=True to gymnasium.make.

Value	Meaning	Value	Meaning	Value	Meaning
0	NOOP	1	FIRE	2	UP
3	RIGHT	4	LEFT	5	DOWN
6	UPFIRE	7	RIGHTFIRE	8	LEFTFIRE
9	DOWNFIRE

Observations

Atari environments have three possible observation types: "rgb", "grayscale" and "ram".

• obs_type="rgb" -> observation_space=Box(0, 255, (210, 160, 3), np.uint8)

• obs_type="ram" -> observation_space=Box(0, 255, (128,), np.uint8)

• obs_type="grayscale" -> Box(0, 255, (210, 160), np.uint8), a grayscale version of the “rgb” type

See variants section for the type of observation used by each environment id by default.

Rewards

You score points by traversing new parts of the grid. Coloring an entire box in the maze or catching chickens gives extra points. For a more detailed documentation, see the AtariAge page.

Variants

Amidar has the following variants of the environment id which have the following differences in observation, the number of frame-skips and the repeat action probability.

Env-id	obs_type=	frameskip=	repeat_action_probability=
Amidar-v0	"rgb"	(2, 5)	0.25
Amidar-ram-v0	"ram"	(2, 5)	0.25
Amidar-ramDeterministic-v0	"ram"	4	0.25
Amidar-ramNoFrameskip-v0	"ram"	1	0.25
AmidarDeterministic-v0	"rgb"	4	0.25
AmidarNoFrameskip-v0	"rgb"	1	0.25
Amidar-v4	"rgb"	(2, 5)	0.0
Amidar-ram-v4	"ram"	(2, 5)	0.0
Amidar-ramDeterministic-v4	"ram"	4	0.0
Amidar-ramNoFrameskip-v4	"ram"	1	0.0
AmidarDeterministic-v4	"rgb"	4	0.0
AmidarNoFrameskip-v4	"rgb"	1	0.0
ALE/Amidar-v5	"rgb"	4	0.25
ALE/Amidar-ram-v5	"ram"	4	0.25

Difficulty and modes

It is possible to specify various flavors of the environment via the keyword arguments difficulty and mode. A flavor is a combination of a game mode and a difficulty setting. The table below lists the possible difficulty and mode values along with the default values.

Available Modes	Default Mode	Available Difficulties	Default Difficulty
[0]	0	[0, 3]	0

Version History

A thorough discussion of the intricate differences between the versions and configurations can be found in the general article on Atari environments.

• v5: Stickiness was added back and stochastic frameskipping was removed. The environments are now in the “ALE” namespace.

• v4: Stickiness of actions was removed

• v0: Initial versions release