Authored by LitDev
Random numbers can be very useful in your Small Basic games. They can be used to make the game play vary from one game to the next.
The Small Basic keyword to get a random number is Math.GetRandomNumber(maxNumber) . It will return a random integer between 1 and the input value maxNumber .
Here are a few ideas and tips:
Random Position and Speed
We can position sprites with random positions and velocities.
radius
=
25
numSprite
=
10
gw
=
GraphicsWindow
.
Width
gh
=
GraphicsWindow
.
Height
For
i
=
1
To
numSprite
sprite
[
i
]
=
Shapes
.
AddEllipse
(
2
*
radius
,
2
*
radius
)
spritePosX
[
i
]
=
radius
+
Math
.
GetRandomNumber
(
gw
-
2
*
radius
)
spritePosY
[
i
]
=
radius
+
Math
.
GetRandomNumber
(
gh
-
2
*
radius
)
spriteVelX
[
i
]
=
Math
.
GetRandomNumber
(
11
)
-
6
spriteVelY
[
i
]
=
Math
.
GetRandomNumber
(
11
)
-
6
EndFor
While
"True"
For
i
=
1
To
numSprite
spritePosX
[
i
]
=
spritePosX
[
i
]
+
spriteVelX
[
i
]
spritePosY
[
i
]
=
spritePosY
[
i
]
+
spriteVelY
[
i
]
If
(
spritePosX
[
i
]
<
radius
)
Then
spritePosX
[
i
]
=
radius
spriteVelX
[
i
]
=
-
spriteVelX
[
i
]
ElseIf
(
spritePosX
[
i
]
>
gw
-
radius
)
Then
spritePosX
[
i
]
=
gw
-
radius
spriteVelX
[
i
]
=
-
spriteVelX
[
i
]
EndIf
If
(
spritePosY
[
i
]
<
radius
)
Then
spritePosY
[
i
]
=
radius
spriteVelY
[
i
]
=
-
spriteVelY
[
i
]
ElseIf
(
spritePosY
[
i
]
>
gh
-
radius
)
Then
spritePosY
[
i
]
=
gh
-
radius
spriteVelY
[
i
]
=
-
spriteVelY
[
i
]
EndIf
Shapes
.
Move
(
sprite
[
i
]
,
spritePosX
[
i
]
-
radius
,
spritePosY
[
i
]
-
radius
)
EndFor
Program
.
Delay
(
20
)
EndWhile
Random Branching
We can randomly do different things in the code, perhaps equivalent to rolling a dice.
dice
=
Math
.
GetRandomNumber
(
6
)
If
(
dice
=
1
)
Then
TextWindow
.
WriteLine
(
"Do something for a dice roll of 1"
)
ElseIf
(
dice
=
2
)
Then
TextWindow
.
WriteLine
(
"Do something for a dice roll of 2"
)
ElseIf
(
dice
=
3
)
Then
TextWindow
.
WriteLine
(
"Do something for a dice roll of 3"
)
ElseIf
(
dice
=
4
)
Then
TextWindow
.
WriteLine
(
"Do something for a dice roll of 4"
)
ElseIf
(
dice
=
5
)
Then
TextWindow
.
WriteLine
(
"Do something for a dice roll of 5"
)
ElseIf
(
dice
=
6
)
Then
TextWindow
.
WriteLine
(
"Do something for a dice roll of 6"
)
EndIf
We could also only do something with a probability, say 1 in 10.
If
(
Math
.
GetRandomNumber
(
10
)
=
1
)
Then
TextWindow
.
WriteLine
(
"This is a 1 in 10 event!!!"
)
Else
TextWindow
.
WriteLine
(
"A 10% probability event didn't happen"
)
EndIf
Ranges and Intervals
If we want random numbers over a different range (not 1 to maxNumber) or with smaller intervals, for example 0.2, then we can use the following formula.
rand
=
min
+
(
Math
.
GetRandomNumber
(
1
+
(
max
-
min
)
/
interval
)
-
1
)
*
interval
Here is an example using this to create random numbers between -5 and 3, with intervals of 0.2.
min
=
-
5
max
=
3
interval
=
0.2
For
i
=
1
To
1000
Random
(
)
TextWindow
.
WriteLine
(
rand
)
EndFor
Sub
Random
rand
=
min
+
(
Math
.
GetRandomNumber
(
1
+
(
max
-
min
)
/
interval
)
-
1
)
*
interval
EndSub
