Riverraid

../../_images/riverraid.gif

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

Action Space

Discrete(18)

Observation Space

Box(0, 255, (210, 160, 3), uint8)

Import

gymnasium.make("ALE/Riverraid-v5")

For more Riverraid variants with different observation and action spaces, see the variants section.

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

Actions

Riverraid has the action space Discrete(18) with the table below listing 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

Value

Meaning

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

See environment specification to see more information on the action meaning.

Observations

Atari environments have three possible observation types: "rgb", "grayscale" and "ram".

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

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

  • obs_type="grayscale" -> Box(0, 255, (210, 160), np.uint8), a grayscale version of the “rgb” type

See variants section for the type of observation used by each environment id by default.

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.

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 frame-skipping was removed. The environments are now in the “ALE” namespace.

  • v4: Stickiness of actions was removed

  • v0: Initial versions release