make brightness values configurable

- Also simplify the cycleBrightness() function with a loop
- Adjusted some of the brightness values

main.go

@@ -67,6 +67,10 @@ type brightnesses struct {
 	outside uint32
 }
 
+var (
+	brightnessSteps = []uint32{0, 255, 100, 20}
+)
+
 const (
 	period         = uint64(1e9 / 500)
 	pressdelay     = time.Millisecond * 500
@@ -228,16 +232,11 @@ func delayChan(inchan <-chan bool, outchan chan<- bool) {
 }
 
 func cycleBrightness(pushchan <-chan bool, brightnesschan chan<- uint32) {
-	brightnesschan <- 0
 	for {
+		for _, b := range brightnessSteps {
+			brightnesschan <- b
 			<-pushchan
-		brightnesschan <- 255
+		}
-		<-pushchan
-		brightnesschan <- 120
-		<-pushchan
-		brightnesschan <- 30
-		<-pushchan
-		brightnesschan <- 0
 	}
 }