自动跟踪目标的旋转炮塔

Option Explicit
Private Type point
  X As Integer
  Y As Integer
End Type

Dim target As point
Dim cur_angle As Single
Dim r As Integer



Private Sub Form_KeyDown(KeyCode As Integer, Shift As Integer)
Select Case KeyCode
  Case Is = 65
    target.X = target.X - 5
    If target.X < 0 Then target.X = 0
  Case Is = 68
    target.X = target.X + 5
    If target.X > 400 Then target.X = 400
  Case Is = 87
    target.Y = target.Y - 5
    If target.Y < 0 Then target.Y = 0
  Case Is = 83
    target.Y = target.Y + 5
    If target.Y > 400 Then target.Y = 400
End Select

 
End Sub

Private Sub Form_Load()
  target.X = 300
  target.Y = 300
  cur_angle = 1.5 * 3.14
  r = 25
  Timer1.Interval = 40
End Sub

Private Sub Form_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
'target.X = X
'target.Y = Y
End Sub

Private Sub Timer1_Timer()
  Form1.Cls
  Form1.Circle (target.X, target.Y), 5
  rotate
  Form1.Caption = cur_angle
End Sub

Function direction(x0, y0, x1, y1 As Integer) As Boolean
  Dim temp As Single
  If x0 = x1 And y1 >= y0 Then temp = 3.14 / 2: GoTo loop1
  If x0 = x1 And y1 < y0 Then temp = 1.5 * 3.14: GoTo loop1

  temp = Atn((y1 - y0) / (x1 - x0))
  If x1 < x0 Then temp = temp + 3.14
  If x1 > x0 And y1 < y0 Then temp = temp + 6.28
  direction = True 'count clockwise
loop1:
  Select Case cur_angle > 3.14
    Case Is = True
      If temp > cur_angle - 3.14 And temp < cur_angle Then direction = False 'clockwise
    Case Is = False
      If temp > cur_angle + 3.14 Or temp < cur_angle Then direction = False
  End Select
End Function

Sub rotate()
  Dim temp As Single
  Dim temp1 As Boolean
  temp1 = direction(200, 200, target.X, target.Y)
  Select Case temp1
    Case Is = False
      temp = -2 * 3.14 / 180
    Case Is = True
      temp = 2 * 3.14 / 180
  End Select
  cur_angle = cur_angle + temp
  If cur_angle > 6.28 Then cur_angle = cur_angle - 6.28
  If cur_angle < 0 Then cur_angle = cur_angle + 6.28
  Line1.X2 = 200 + r * Cos(cur_angle)
  Line1.Y2 = 200 + r * Sin(cur_angle)

End Sub