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 Shape

(210, 160, 3)

Observation High

255

Observation Low

0

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 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

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

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.

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