Amidar#

../../../_images/amidar.gif

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

Action Space

Discrete(10)

Observation Shape

(210, 160, 3)

Observation High

255

Observation Low

0

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 Discrete(10) with the table below lists the meaning of each action’s meanings. As Amidar uses a reduced set of actions for v0, v4 and v5 versions of the environment. 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 environment have two possible observation types, the observation space is listed below. See variants section for the type of observation used by each environment id.

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

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

Additionally, obs_type="grayscale" cause the environment return a grayscale version of the rgb array for observations with the observation space being Box(0, 255, (210, 160), np.uint8)

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