;-------------------------------------------------------------------------------

; Trigonometry: return horizontal vector
Function VectorX# ( Distance# , Angle# )
    Return Sin ( Angle ) * Distance
End Function

; Trigonometry: return vertical vector
Function VectorY# ( Distance# , Angle# )
    Return Sin ( Angle - 90 ) * Distance
End Function

; Trigonometry: return distance using vector
Function VectorDistance# ( X# , Y# )
    Return Sqr ( X * X + Y * Y )
End Function

; Trigonometry: return angle using vector
Function VectorAngle# ( X# , Y# )
    Return 180 - Atan2 ( X , Y )
End Function

;-------------------------------------------------------------------------------

; Blitz graphics window mode states
Const WindowMode_AutoDetect = 0
Const WindowMode_FullScreen = 1
Const WindowMode_Windowed   = 2
Const WindowMode_Scaled     = 3

; Desired screen settings
Const ScreenWidth  = 640
Const ScreenHeight = 480
Const ColorDepth   = 0
Const WindowMode   = WindowMode_AutoDetect

; Ship motion control
Const KeyUp    = 200
Const KeyDown  = 208
Const KeyLeft  = 203
Const KeyRight = 205
; Game control
Const KeyEsc   =   1

; Ship thrust speed in pixels per frame
Const ThrustSpeed# = 0.12
; Ship rotation speed in degrees per frame
Const RotateSpeed# = 4
; Ship maximum velocity in pixels per frame
Const MaxSpeed     = 5

;-------------------------------------------------------------------------------

; Ship position
Local PosX#
Local PosY#

; Current ship angle
Local Angle#
; Current ship heading (direction)
Local Heading#
; Current ship speed (velocity)
Local Speed#

; Ship speed vector
Local SpeedX#
Local SpeedY#

; Ship thrust vector
Local ThrustX#
Local ThrustY#

; Original ship image (pointing upwards)
Local ShipImage
; Temporarily rotated ship (any direction)
Local RotatedShipImage

;-------------------------------------------------------------------------------

; Setup screen
Graphics ScreenWidth , ScreenHeight , ColorDepth , WindowMode
SetBuffer BackBuffer ()

; Load and center ship image
ShipImage = LoadImage ( "Ship Pre Final.PNG" )
MidHandle ShipImage

; Disable rotation/scaling smoothing
TFormFilter False 

; Start in center of screen
PosX = ScreenWidth  / 2
PosY = ScreenHeight / 2

Repeat

    ; Input

    ; - Rotate left
    If KeyDown ( KeyLeft )
        Angle = Angle - RotateSpeed
        If Angle < 0 Then Angle = Angle + 360
    EndIf

    ; - Rotate right
    If KeyDown ( KeyRight )
        Angle = Angle + RotateSpeed
        If Angle >= 360 Then Angle = Angle - 360
    EndIf

    ; - Thrust
    If KeyDown ( KeyDown )
        ; Combine thrust speed and ship angle to make the thrust vector
        ThrustX = VectorX ( ThrustSpeed , Angle )
        ThrustY = VectorY ( ThrustSpeed , Angle )
    Else 
        ; Reset thrust vector
        ThrustX = 0
        ThrustY = 0
    EndIf

    ; Update

    ; - Take the current velocity vector (speed and heading)
    ; - Then add the thrust vector to it (thrust and angle)
    ; - Which becomes the new velocity vector
    SpeedX = VectorX ( Speed , Heading ) + ThrustX
    SpeedY = VectorY ( Speed , Heading ) + ThrustY

    ; - Now update the current speed and heading with the new velocity vector
    Speed = VectorDistance ( SpeedX , SpeedY )
    Heading = VectorAngle ( SpeedX , SpeedY )

    ; - Limit the speed to the maximum
    If Speed > MaxSpeed
        Speed = MaxSpeed

        ; Apply the new speed to the velocity vector
        SpeedX = VectorX ( Speed , Heading )
        SpeedY = VectorY ( Speed , Heading )
    EndIf 

    ; - Finally add the velocity vector to the ship position
    PosX = PosX + SpeedX
    PosY = PosY + SpeedY

    ; - Screen edge wrap when crossing screen boundaries
    If PosX < 0
        PosX = PosX + ScreenWidth
    ElseIf PosX >= ScreenWidth
        PosX = PosX - ScreenWidth
    EndIf 
    If PosY < 0
        PosY = PosY + ScreenHeight
    ElseIf PosY >= ScreenHeight
        PosY = PosY - ScreenHeight
    EndIf 

    ; Render

    Cls

    ; - Ship image
    ;   - Duplicate the original image
    RotatedShipImage = CopyImage ( ShipImage )
    ;   - Rotate it to the current angle
    RotateImage RotatedShipImage , Angle
    ;   - Then draw it on screen
    DrawImage RotatedShipImage , PosX , PosY
    ;   - And clear the rotated image
    FreeImage RotatedShipImage

    Flip

Until KeyHit( KeyEsc )

; Blitz automagically cleans up
End