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93 lines
4.9 KiB
Markdown
93 lines
4.9 KiB
Markdown
---
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title: Asterix
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---
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# Asterix
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```{figure} ../../_static/videos/atari/asterix.gif
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:width: 120px
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:name: Asterix
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```
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This environment is part of the <a href='..'>Atari environments</a>. Please read that page first for general information.
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| Action Space | Discrete(9) |
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| Observation Space | Box(0, 255, (210, 160, 3), uint8) |
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| Import | `gymnasium.make("ALE/Asterix-v5")` |
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For more Asterix variants with different observation and action spaces, see the variants section.
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## Description
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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.
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For a more detailed documentation, see [the AtariAge page](https://atariage.com/manual_html_page.php?SoftwareID=3325)
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## Actions
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Asterix has the action space of `Discrete(9)` with the table below listing the meaning of each action's meanings.
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To enable all 18 possible actions that can be performed on an Atari 2600, specify `full_action_space=True` during
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initialization or by passing `full_action_space=True` to `gymnasium.make`.
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| Value | Meaning | Value | Meaning | Value | Meaning |
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|---------|-----------|---------|-------------|---------|------------|
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| `0` | `NOOP` | `1` | `UP` | `2` | `RIGHT` |
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| `3` | `LEFT` | `4` | `DOWN` | `5` | `UPRIGHT` |
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| `6` | `UPLEFT` | `7` | `DOWNRIGHT` | `8` | `DOWNLEFT` |
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## Observations
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Atari environments have three possible observation types: `"rgb"`, `"grayscale"` and `"ram"`.
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- `obs_type="rgb" -> observation_space=Box(0, 255, (210, 160, 3), np.uint8)`
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- `obs_type="ram" -> observation_space=Box(0, 255, (128,), np.uint8)`
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- `obs_type="grayscale" -> Box(0, 255, (210, 160), np.uint8)`, a grayscale version of the "rgb" type
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See variants section for the type of observation used by each environment id by default.
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### Rewards
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A table of scores awarded for collecting the different objects is provided on [the AtariAge page](https://atariage.com/manual_html_page.php?SoftwareID=3325).
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## Variants
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Asterix has the following variants of the environment id which have the following differences in observation,
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the number of frame-skips and the repeat action probability.
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| Env-id | obs_type= | frameskip= | repeat_action_probability= |
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|-----------------------------|-------------|--------------|------------------------------|
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| Asterix-v0 | `"rgb"` | `(2, 5)` | `0.25` |
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| Asterix-ram-v0 | `"ram"` | `(2, 5)` | `0.25` |
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| Asterix-ramDeterministic-v0 | `"ram"` | `4` | `0.25` |
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| Asterix-ramNoFrameskip-v0 | `"ram"` | `1` | `0.25` |
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| AsterixDeterministic-v0 | `"rgb"` | `4` | `0.25` |
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| AsterixNoFrameskip-v0 | `"rgb"` | `1` | `0.25` |
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| Asterix-v4 | `"rgb"` | `(2, 5)` | `0.0` |
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| Asterix-ram-v4 | `"ram"` | `(2, 5)` | `0.0` |
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| Asterix-ramDeterministic-v4 | `"ram"` | `4` | `0.0` |
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| Asterix-ramNoFrameskip-v4 | `"ram"` | `1` | `0.0` |
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| AsterixDeterministic-v4 | `"rgb"` | `4` | `0.0` |
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| AsterixNoFrameskip-v4 | `"rgb"` | `1` | `0.0` |
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| ALE/Asterix-v5 | `"rgb"` | `4` | `0.25` |
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| ALE/Asterix-ram-v5 | `"ram"` | `4` | `0.25` |
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## Difficulty and modes
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It is possible to specify various flavors of the environment via the keyword arguments `difficulty` and `mode`.
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A flavor is a combination of a game mode and a difficulty setting. The table below lists the possible difficulty and mode values
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along with the default values.
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| Available Modes | Default Mode | Available Difficulties | Default Difficulty |
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|-------------------|----------------|--------------------------|----------------------|
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| `[0]` | `0` | `[0]` | `0` |
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## Version History
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A thorough discussion of the intricate differences between the versions and configurations can be found in the general article on Atari environments.
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* v5: Stickiness was added back and stochastic frameskipping was removed. The environments are now in the "ALE" namespace.
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* v4: Stickiness of actions was removed
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* v0: Initial versions release
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