Gymnasium/docs/environments/atari/demon_attack.md

---
title: Demon Attack
---
# Demon Attack

```{figure} ../../_static/videos/atari/demon_attack.gif 
:width: 120px
:name: DemonAttack
```

This environment is part of the <a href='..'>Atari environments</a>. Please read that page first for general information.

|   |   |
|---|---|
| Action Space | Discrete(18) |
| Observation Space | (210, 160, 3) |
| Observation High | 255 |
| Observation Low | 0 |
| Import | `gymnasium.make("ALE/DemonAttack-v5")` | 

### Description
You are facing waves of demons in the ice planet of Krybor. Points are accumulated by destroying
demons. You begin with 3 reserve bunkers, and can increase its number (up to 6) by avoiding enemy
attacks. Each attack wave you survive without any hits, grants you a new bunker. Every time an enemy
hits you, a bunker is destroyed. When the last bunker falls, the next enemy hit will destroy you and
the game ends.

Detailed documentation can be found on [the AtariAge page](https://atariage.com/manual_html_page.php?SoftwareLabelID=135).

### Actions
By default, all actions that can be performed on an Atari 2600 are available in this environment.
However, if you use v0 or v4 or specify `full_action_space=False` during initialization, only a reduced
number of actions (those that are meaningful in this game) are available. The reduced action space may depend
on the flavor of the environment (the combination of `mode` and `difficulty`). The reduced action space for the default 
flavor looks like this:

| Num | Action                 |
|-----|------------------------|
| 0   | NOOP |
| 1   | UP |
| 2   | RIGHT |
| 3   | LEFT |
| 4   | DOWN |  
| 5   | UPRIGHT |
| 6   | UPLEFT |
| 7   | DOWNRIGHT |
| 8   | DOWNLEFT |

### Observations
By default, the environment returns the RGB image that is displayed to human players as an observation. However, it is
possible to observe
- The 128 Bytes of RAM of the console
- A grayscale image

instead. The respective observation spaces are
- `Box([0 ... 0], [255 ... 255], (128,), uint8)`
- `Box([[0 ... 0]
 ...
 [0  ... 0]], [[255 ... 255]
 ...
 [255  ... 255]], (250, 160), uint8)
`

respectively. The general article on Atari environments outlines different ways to instantiate corresponding environments
via `gymnasium.make`.

### Rewards
Each enemy you slay gives you points. The amount of points depends on the type of demon and which
wave you are in. A detailed table of scores is provided on [the AtariAge
page](https://atariage.com/manual_html_page.php?SoftwareLabelID=135).

### Arguments

```
env = gymnasium.make("ALE/DemonAttack-v5")
```

The various ways to configure the environment are described in detail in the article on Atari environments.
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.

|      Environment | Valid Modes                                                                                                                                                                         | Valid Difficulties | Default Mode |
|------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------|--------------|
|      DemonAttack | `[1, 3, 5, 7]`                                                                                                                                                                      |           `[0, 1]` | `1`          |

You may use the suffix "-ram" to switch to the RAM observation space. In v0 and v4, the suffixes "Deterministic" and "Noframeskip" 
are available. These are no longer supported in v5. In order to obtain equivalent behavior, pass keyword arguments to `gymnasium.make` as outlined in 
the general article on Atari environments.
The versions v0 and v4 are not contained in the "ALE" namespace. I.e. they are instantiated via `gymnasium.make("DemonAttack-v0")`.

### 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 entire action space is used by default. The environments are now in the "ALE" namespace.
* v4: Stickiness of actions was removed
* v0: Initial versions release (1.0.0)