STGL (ShooTing Game Language)

= language to define the action of the ACTORs in the 2D shooting game.

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Language reference

ACTOR and FUNCTION

ACTOR

= object such as the bullet, turret, enemy or stage-pattern controlled by the FUNCTION.

FUNCTION

= composed of the FUNCTION_NAME, FUNCTION_ARGUMENTs and the SCRIPT described in the indentation block.

[format]

FUNCTION_NAME FUNCTION_ARGUMENT, FUNCTION_ARGUMENT, ...
        SCRIPT

[example]

straightBullet a, s
        @angle = a
        @speed = s

SCRIPT

= sequcence of COMMANDs (e.g. fire the bullet, vanish in certain timing, change the position, angle or speed) to control the ACTOR.

COMMAND

= composed of the COMMAND_NAME and COMMAND_ARGUMENTs.

[format]

COMMAND_NAME COMMAND_ARGUMENT, COMMAND_ARGUMENT, ...

[example]

straightBullet 90, 0.02
vanish
@y += 0.01

COMMAND_NAME

= one of below-listed strings.

[command name list]

• VARIABLE = (set)
• VARIABLE += (incrementBy)
• VARIABLE -= (decrementBy)
• VARIABLE <= (set the steady-state value)
• VARIABLE <+= (set the steady-state increment value)
• VARIABLE <-= (set the steady-state decrement value)
• VARIABLE => (set the target value)
• vanish (vanish the ACTOR)
• wait (wait executing the SCRIPT)
• waitUntil (wait executing the SCRIPT conditionally)
• notify (suspend the waiting state of other ACTORs)
• repeat (repeat the CHILD_SCRIPT)
• while (repeat the CHILD_SCRIPT conditionally)
• FUNCTION_NAME (add another ACTOR)

VARIABLE = VALUE

= set the VALUE to the VARIABLE (e.g. position, angle or speed of this ACTOR).

[example]

@x = 0.2

VARIABLE += VALUE

= increment the VARIABLE by the VALUE.

[example]

@speed += 0.1

VARIABLE -= VALUE

= decrement the VARIABLE by the VALUE.

VARIABLE <= VALUE

= set the VALUE to VARIABLE every frame.

[example]

@x <= cos(@y * 0.001) * 0.4 + 0.5

(means the value of VARIABLE @x is set to the calculation result of the expression 'cos(@y * 0.001) * 0.4 + 0.5' every frame)

VARIABLE <+= VALUE

= increment the VARIABLE by the VALUE every frame.

[example]

@x <+= 0.01

(increments the value of the VARIABLE @x by 0.01 every frame)

VARIABLE <-= VALUE

= decrement the VARIABLE by the VALUE every frame.

VARIABLE => VALUE, VALUE(2)

= set the VALUE to the VARIABLE in a time span of VALUE(2) frames (1 frame = 1/60 sec.).

[example]

@y => 0.5, 120

(means the value of the VARIABLE @y changes from the current value to 0.5 linearly in a time span of 120 frames)

vanish

= vanish this actor.

vanish FUNCTION_NAME

= vanish CHILD_ACTORs having the FUNCTION_NAME.

(CHILD_ACTOR = ACTORs added by this ACTOR.)

wait {VALUE = $inf}

= wait executing the SCRIPT for VALUE frames.

{COMMAND_ARGUMENT = default value} = optional argument having the default value.

waitUntil {VALUE = 0}

= wait until VALUE becomes 1 (true).

notify

= suspend the waiting state of the PARENT_ACTOR.

notify FUNCTION_NAME

= suspend the waiting state of the CHILD_ACTOR having the FUNCTION_NAME.

(PARENT_ACTOR = ACTOR added this ACTOR.)

repeat {VALUE = $inf}

= repeat the CHILD_SCRIPT VALUE times.

(CHILD_SCRIPT= indentation blocks after the COMMAND.)

[example]

repeat 10
        fire a, s
        a += av / 10
        s += sv / 10

(SCRIPT from 'fire a, s' to 's += sv / 10' is the CHILD_SCRIPT)

while {VALUE = 1}

= repeat the CHILD_SCRIPT until VALUE becomes 0 (false).

FUNCTION_NAME FUNCTION_ARGUMENT_VALUE, FUNCTION_ARGUMENT_VALUE, ...

= add another ACTOR controlled by the FUNCTION corresponding the FUNCTION_NAME with FUNCTION_ARGUMENT_VALUEs.

[example]

waveEnemy
        @x <= cos(@y * 800) * 0.4 + 0.5
        @y <+= 0.003
        repeat
                downwardBullet 0.02
                wait 30
downwardBullet s
        @angle = 0
        @speed = s

(means the 'waveEnemy' fires the 'downwardBullet' every 30 frames)

VARIABLE and VALUE

VARIABLE

= below-listed actor variable or string represents the user defined variable.

[actor variable]

• @x (x-coordinate of the position of this ACTOR) (=0 means the left edge of the screen, =1 means the right edge)
• @y (y-coordinate of the position of this ACTOR) (=0 means top, =1 means bottom)
• @angle (direction of movement of this ACTOR) (=0 means downward, =90 means rightward, =180 means upward, =270 means leftward)
• @speed (speed of movement of this ACTOR)

[example]

@speed
a
appFlag1

VALUE

= float value, VARIABLE, below-listed read-only variable or expression consists of OPERATORS and VALUEs.

[read-only variable]

• $playerX, $px (x-coordinate of the position of the PLAYER)
• $playerY, $py (y-coordinate of the position of the PLAYER)
• $enemyCount, $ec (total numbers of enemies on the screen)
• $angleToPlayer, $atp (angle from this ACTOR to the PLAYER)
• $distanceToPlayer, $dtp (distance from this ACTOR to the PLAYER)
• $ticks, $t (frame ticks from this ACTOR is generated)
• $parentX, $prx (x-coordinate of the position of the PARENT_ACTOR)
• $parentY, $pry (y-coordinate of the position of the PARENT_ACTOR)
• $infinity, $inf (infinite value)

[example]

-4.2
@angle + 180
$playerY < 0.5 ? -1 : 1

(PLAYER = object controlled by the player (e.g. my ship, tank or fighter))

OPERATORS

= operators to calc the float value.

[operators]

• +, -, *, /, % (Arithmetic operations)
• V1..V2 (Get a random integer value from V1 to V2)
• V1__V2 (Get a random float value from V1 to V2)
• V1|V2 (Get V1 or V2 fifty-fifty)
• ==, !=, >, >=, <, <= (Comparison operations) (1 means true, 0 means false)
• !, &&, || (Logical operations)
• ? : (Conditional operator)
• () (Bracket)
• sin(), cos() (Trigonometric function)

ACTOR_TYPE, COMMENT and MAIN_FUNCTION

ACTOR_TYPE

= described in front of FUNCTIONs of stage, enemy, turret or bullet ACTORs.

[actor type]

• :stage (sets up enemies in the stage)
• :enemy (moves on the game screen and fires bullets)
• :turret (moves together with the enemy and fires bullets)
• :bullet (is fired toward the PLAYER)

COMMENT

= characters after '#'.

[example]

wait 2 # this is a comment.

MAIN_FUNCTION

= bootstrap FUNCTION.

[example]

main
        addWaves 10

License

Copyright © 2013 ABA Games

Distributed under the MIT License.