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title
| title |
|---|
| Asterix |
Asterix
:width: 120px
:name: Asterix
This environment is part of the Atari environments. Please read that page first for general information.
Description
You are Asterix and can move horizontally (continuously) and vertically (discretely). Objects move horizontally across the screen: lyres and other (more useful) objects. Your goal is to guideAsterix in such a way as to avoid lyres and collect as many other objects as possible. You score points by collecting objects and lose a life whenever you collect a lyre. You have three lives available at the beginning. If you score sufficiently many points, you will be awarded additional points.
For a more detailed documentation, see the AtariAge page
Actions
Asterix has the action space Discrete(9) with the table below lists the meaning of each action's meanings.
As Asterix 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 |
|---|---|
0 |
NOOP |
1 |
UP |
2 |
RIGHT |
3 |
LEFT |
4 |
DOWN |
5 |
UPRIGHT |
6 |
UPLEFT |
7 |
DOWNRIGHT |
8 |
DOWNLEFT |
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
A table of scores awarded for collecting the different objects is provided on the AtariAge page.
Variants
Asterix 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= |
|---|---|---|---|
| Asterix-v0 | "rgb" |
(2, 5) |
0.25 |
| Asterix-ram-v0 | "ram" |
(2, 5) |
0.25 |
| Asterix-ramDeterministic-v0 | "ram" |
4 |
0.25 |
| Asterix-ramNoFrameskip-v0 | "ram" |
1 |
0.25 |
| AsterixDeterministic-v0 | "rgb" |
4 |
0.25 |
| AsterixNoFrameskip-v0 | "rgb" |
1 |
0.25 |
| Asterix-v4 | "rgb" |
(2, 5) |
0.0 |
| Asterix-ram-v4 | "ram" |
(2, 5) |
0.0 |
| Asterix-ramDeterministic-v4 | "ram" |
4 |
0.0 |
| Asterix-ramNoFrameskip-v4 | "ram" |
1 |
0.0 |
| AsterixDeterministic-v4 | "rgb" |
4 |
0.0 |
| AsterixNoFrameskip-v4 | "rgb" |
1 |
0.0 |
| ALE/Asterix-v5 | "rgb" |
4 |
0.25 |
| ALE/Asterix-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] |
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