I used the distance equation in this little game (also in code archives...Doesn't use true vectors but I think it will help.
Type point2
Field x#,y#
Field angle#
Field xvel#,yvel#
Field xthrust#,ythrust#,crash#
Field image
End Type
Type point1
Field angle#
Field x#,y#
Field x_velocity#, y_velocity#
Field crash#,thrustx#,thrusty#
Field image
End Type
Local speed# = 1
Local number_enemies = 1
Const change# = .2
Const vel# = 1.5
Graphics 800,600, 0, 2
SetBuffer BackBuffer()
AutoMidHandle(True)
Cls:Flip
font = LoadFont("arial",24)
SetFont font
Locate GraphicsWidth()/3,GraphicsHeight()/2
Color 255,255,255
number_enemies = Input("How many enemies? ")
SeedRnd MilliSecs()
Global Pos.point1 = New point1; Current position.
Pos\x = GraphicsWidth()/2: Pos\y = GraphicsHeight()/2
Pos\crash = 0
Pos\x_velocity = 0 : Pos\y_velocity = 0
Pos\image = LoadImage("blue dot.bmp") ;edit this out if you don't have images
For i = 1 To number_enemies
enemy.point2 = New point2 ; enemy position
Repeat
enemy\x = Rand(1,GraphicsWidth()): enemy\y = Rand(1,GraphicsHeight())
Until Not (enemy\x + 5 < Pos\x-10 And enemy\y + 5 < Pos\y-10 And enemy\x - 5 > Pos\x+10 And enemy\y - 5 > Pos\y+10)
enemy\image = LoadImage("red dot.bmp") ;edit this out if you don't have images
enemy\crash = False
Next
Repeat:Flip:Cls
update_player()
update_computer()
If Pos\crash = 1 Then
counter = counter + 1
EndIf
If counter = 100 Then
counter = 0
Pos\crash = 0
EndIf
Until KeyHit(1)
End
Function update_player()
Local old_x = Pos\x
Local old_y = Pos\y
Local old_xv = Pos\x_velocity
Local old_yv = Pos\y_velocity
Pos\thrustx = 0
Pos\thrusty = 0
If Pos\crash = 1 Then
If KeyDown(203) Then Pos\thrustx = -2
If KeyDown(200) Then Pos\thrusty = -2
If KeyDown(208) Then Pos\thrusty = 2
If KeyDown(205) Then Pos\thrustx = 2
If Pos\thrustx > Pos\x_velocity Then Pos\x_velocity = Pos\x_velocity + change
If Pos\thrustx < Pos\x_velocity Then Pos\x_velocity = Pos\x_velocity - change
If Pos\thrusty > Pos\y_velocity Then Pos\y_velocity = Pos\y_velocity + change
If Pos\thrusty < Pos\y_velocity Then Pos\y_velocity = Pos\y_velocity - change
If Pos\x_velocity = 0 And Pos\y_velocity = 0 Then Pos\crash = 0
Else ;if crash = 0
Pos\x_velocity = 0
Pos\y_velocity = 0
If KeyDown(203) Then Pos\x_velocity = -2
If KeyDown(200) Then Pos\y_velocity = -2
If KeyDown(208) Then Pos\y_velocity = 2
If KeyDown(205) Then Pos\x_velocity = 2
If Pos\x_velocity <> 0 Or Pos\y_velocity <> 0 Then Pos\crash = 1
EndIf
Pos\x = Pos\x + Pos\x_velocity
Pos\y = Pos\y + Pos\y_velocity
If Pos\x + 10 > GraphicsWidth() Or Pos\x - 10 < 0 Or Pos\y + 10 > GraphicsHeight() Or Pos\y - 5 < 10 Then
player_lose()
EndIf
For enemy_dot.point2 = Each point2
size = 10
dx#=(enemy_dot\x-Pos\x)
dy#=(enemy_dot\y-Pos\y)
distance#=Sqr(dx*dx+dy*dy)
If distance<size+5
dx=dx/distance
dy=dy/distance
dz=dz/distance
Pos\x_velocity = -dx*2.5*vel
Pos\y_velocity = -dy*2.5*vel
enemy_dot\xvel = dx*10*vel
enemy_dot\yvel = dy*10*vel
Pos\crash = 1
EndIf
Next
DrawImage(Pos\image,Pos\x,Pos\y); Draw sprite (edit out if you don't have images)
;Color 0,0,255 ;put in if you don't have images
;Oval Pos\x-10,Pos\y-10,20,20 ;put in if you don't have images
End Function
Function update_computer()
Local counter = 0
For enemy_dot.point2 = Each point2
counter = counter + 1
size = 10
dx#=(Pos\x-enemy_dot\x)
dy#=(Pos\y-enemy_dot\y)
distance#=Sqr(dx*dx+dy*dy)
dx=dx/distance
dy=dy/distance
enemy_dot\xthrust = dx*vel
enemy_dot\ythrust = dy*vel
For enemydot.point2=Each point2
If enemydot<>enemy_dot
dx#=(enemydot\x-enemy_dot\x)
dy#=(enemydot\y-enemy_dot\y)
distance=Sqr(dx*dx+dy*dy)
If distance<size
dx=dx/distance
dy=dy/distance
enemy_dot\xvel = -dx*5*vel
enemy_dot\yvel = -dy*5*vel
enemydot\xvel = dx*5*vel
enemydot\yvel = dy*5*vel
EndIf
EndIf
Next
dx#=(Pos\x-enemy_dot\x)
dy#=(Pos\y-enemy_dot\y)
distance#=Sqr(dx*dx+dy*dy)
If distance<size+5
dx=dx/distance
dy=dy/distance
enemy_dot\xvel = -dx*5*vel
enemy_dot\yvel = -dy*5*vel
Pos\x_velocity = dx*2.5*vel
Pos\y_velocity = dy*2.5*vel
EndIf
If enemy_dot\crash = 1 Then
If enemy_dot\xthrust > enemy_dot\xvel Then enemy_dot\xvel = enemy_dot\xvel + change
If enemy_dot\xthrust < enemy_dot\xvel Then enemy_dot\xvel = enemy_dot\xvel - change
If enemy_dot\ythrust > enemy_dot\yvel Then enemy_dot\yvel = enemy_dot\yvel + change
If enemy_dot\ythrust < enemy_dot\yvel Then enemy_dot\yvel = enemy_dot\yvel - change
If enemy_dot\xvel = 0 And enemy_dot\yvel = 0 Then enemy_dot\crash = 0
Else
enemy_dot\xvel = enemy_dot\xthrust
enemy_dot\yvel = enemy_dot\ythrust
If enemy_dot\xvel <> 0 Or enemy_dot\yvel <> 0 Then enemy_dot\crash = 1
EndIf
enemy_dot\x = enemy_dot\x + enemy_dot\xvel
enemy_dot\y = enemy_dot\y + enemy_dot\yvel
DrawImage enemy_dot\image,enemy_dot\x,enemy_dot\y ;edit out if you don't have images
;Color 255,0,0 ;put on if you don't have images
;Oval enemy_dot\x-5,enemy_dot\y-5,10,10 ;put on if you don't have images
If enemy_dot\x+5 > GraphicsWidth() Or enemy_dot\x-5 < 0 Or enemy_dot\y+5 > GraphicsHeight() Or enemy_dot\y-5 < 0 Then
FreeImage enemy_dot\image
Delete enemy_dot
EndIf
Next
If counter = 0 Then
Player_wins()
EndIf
End Function
Function player_lose()
Color 0,0,255
font = LoadFont("arial",48)
SetFont(font)
Cls:Flip
Text GraphicsWidth()/2,GraphicsHeight()/2,"You Lose",1,1
Flip
Delay 2000
For enemy_dot.point2 = Each point2
FreeImage enemy_dot\image
Delete enemy_dot
Next
FreeImage Pos\image
Delete Pos
End
End Function
Function Player_wins()
Color 0,0,255
font = LoadFont("arial",48)
SetFont(font)
Cls:Flip
Text GraphicsWidth()/2,GraphicsHeight()/2,"You Win",1,1
Flip
Delay 2000
For enemy_dot.point2 = Each point2
FreeImage enemy_dot\image
Delete enemy_dot
Next
FreeImage Pos\image
Delete Pos
End
End Function