---
title: Riverraid
---

# Riverraid

```{figure} ../../_static/videos/atari/riverraid.gif
:width: 120px
:name: Riverraid
```

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

## Description

You control a jet that flies over a river: you can move it sideways and fire missiles to destroy enemy objects. Each time an enemy object is destroyed you score points (i.e. rewards).You lose a jet when you run out of fuel: fly over a fuel depot when you begin to run low.You lose a jet even when it collides with the river bank or one of the enemy objects (except fuel depots).The game begins with a squadron of three jets in reserve and you're given an additional jet (up to 9) for each 10,000 points you score.

For a more detailed documentation, see [the AtariAge page](https://atariage.com/manual_html_page.php?SoftwareLabelID=409)

## Actions

Riverraid has the action space `Discrete(18)` with the table below lists the meaning of each action's meanings.
As Riverraid uses the full set of actions then specifying `full_action_space=True` will not modify the action space of the environment if passed to `gymnasium.make`.

| Value   | Meaning         |
|---------|-----------------|
| `0`     | `NOOP`          |
| `1`     | `FIRE`          |
| `2`     | `UP`            |
| `3`     | `RIGHT`         |
| `4`     | `LEFT`          |
| `5`     | `DOWN`          |
| `6`     | `UPRIGHT`       |
| `7`     | `UPLEFT`        |
| `8`     | `DOWNRIGHT`     |
| `9`     | `DOWNLEFT`      |
| `10`    | `UPFIRE`        |
| `11`    | `RIGHTFIRE`     |
| `12`    | `LEFTFIRE`      |
| `13`    | `DOWNFIRE`      |
| `14`    | `UPRIGHTFIRE`   |
| `15`    | `UPLEFTFIRE`    |
| `16`    | `DOWNRIGHTFIRE` |
| `17`    | `DOWNLEFTFIRE`  |

## 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

Score points are your only reward. You get score points each time you destroy an enemy object:

| Enemy Object | Score Points |
|--------------|--------------|
| Tanker       | 30           |
| Helicopter   | 60           |
| Fuel Depot   | 80           |
| Jet          | 100          |
| Bridge       | 500          |

For a more detailed documentation, see [the AtariAge page](https://atariage.com/manual_html_page.php?SoftwareLabelID=409).

## Variants

Riverraid 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=   |
|-------------------------------|-------------|--------------|------------------------------|
| Riverraid-v0                  | `"rgb"`     | `(2, 5)`     | `0.25`                       |
| Riverraid-ram-v0              | `"ram"`     | `(2, 5)`     | `0.25`                       |
| Riverraid-ramDeterministic-v0 | `"ram"`     | `4`          | `0.25`                       |
| Riverraid-ramNoFrameskip-v0   | `"ram"`     | `1`          | `0.25`                       |
| RiverraidDeterministic-v0     | `"rgb"`     | `4`          | `0.25`                       |
| RiverraidNoFrameskip-v0       | `"rgb"`     | `1`          | `0.25`                       |
| Riverraid-v4                  | `"rgb"`     | `(2, 5)`     | `0.0`                        |
| Riverraid-ram-v4              | `"ram"`     | `(2, 5)`     | `0.0`                        |
| Riverraid-ramDeterministic-v4 | `"ram"`     | `4`          | `0.0`                        |
| Riverraid-ramNoFrameskip-v4   | `"ram"`     | `1`          | `0.0`                        |
| RiverraidDeterministic-v4     | `"rgb"`     | `4`          | `0.0`                        |
| RiverraidNoFrameskip-v4       | `"rgb"`     | `1`          | `0.0`                        |
| ALE/Riverraid-v5              | `"rgb"`     | `4`          | `0.25`                       |
| ALE/Riverraid-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, 1]`                 | `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