func drawNiddles(ctx *canvas.CanvasRenderingContext2D, r int) {
hourR := float64(r - 30)
minuteR := float64(r - 20)
secondR := float64(r - 13)
now := time.Now()
hourAngle := (1 - float64(now.Hour()%12)/12) * math.Pi * 2
minuteAngle := (1 - float64(now.Minute())/60) * math.Pi * 2
secondAngle := (1 - float64(now.Second())/60) * math.Pi * 2
rotateAngle := math.Pi
ctx.Save()
ctx.Rotate(int(-1 * rotateAngle))
ctx.StrokeStyle = "black"
ctx.LineWidth = 4
ctx.MoveTo(0, 0)
ctx.LineTo(int(hourR*math.Sin(hourAngle)), int(hourR*math.Cos(hourAngle)))
ctx.Stroke()
ctx.LineWidth = 2
ctx.MoveTo(0, 0)
ctx.LineTo(int(minuteR*math.Sin(minuteAngle)), int(minuteR*math.Cos(minuteAngle)))
ctx.Stroke()
ctx.LineWidth = 1
ctx.MoveTo(0, 0)
ctx.LineTo(int(secondR*math.Sin(secondAngle)), int(secondR*math.Cos(secondAngle)))
ctx.Stroke()
ctx.Restore()
}
func drawClockPane(ctx *canvas.CanvasRenderingContext2D, r int) {
ctx.Save()
// cycle
ctx.StrokeStyle = "black"
ctx.LineWidth = 4
ctx.BeginPath()
ctx.Arc(0, 0, r, 0., float32(2*math.Pi), true)
ctx.ClosePath()
ctx.Stroke()
// hour tick
itv := 2 * math.Pi / 12.0
r0 := float64(r - 10)
r1 := float64(r)
for i := 0; i < 12; i++ {
angle := float64(i) * itv
ctx.MoveTo(int(r0*math.Sin(angle)), int(r0*math.Cos(angle)))
ctx.LineTo(int(r1*math.Sin(angle)), int(r1*math.Cos(angle)))
ctx.Stroke()
}
// minute tick
ctx.LineWidth = 2
itv = 2 * math.Pi / 60.0
r0 = float64(r - 5)
r1 = float64(r)
for i := 0; i < 60; i++ {
angle := float64(i) * itv
ctx.MoveTo(int(r0*math.Sin(angle)), int(r0*math.Cos(angle)))
ctx.LineTo(int(r1*math.Sin(angle)), int(r1*math.Cos(angle)))
ctx.Stroke()
}
ctx.Restore()
}