add spooky rainbows for @guru

micropython/examples/plasma_stick/cheerlights.py

@@ -33,9 +33,34 @@ def status_handler(mode, status, ip):
             print('Connection successful!')
         else:
             print('Connection failed!')
-            # light up red if connection fails
-            for i in range(NUM_LEDS):
-                led_strip.set_rgb(i, 255, 0, 0)
+            # if no wifi connection, you get spooky rainbows. Bwahahaha!
+            spooky_rainbows()
+
+
+def spooky_rainbows():
+    print("SPOOKY RAINBOWS!")
+    HUE_START = 30  # orange
+    HUE_END = 140  # green
+    SPEED = 0.3  # bigger = faster (harder, stronger)
+
+    distance = 0.0
+    direction = SPEED
+    while True:
+        for i in range(NUM_LEDS):
+            # generate a triangle wave that moves up and down the LEDs
+            j = max(0, 1 - abs(distance - i) / (NUM_LEDS / 3))
+            hue = HUE_START + j * (HUE_END - HUE_START)
+
+            led_strip.set_hsv(i, hue / 360, 1.0, 0.8)
+
+        # reverse direction at the end of colour segment to avoid an abrupt change
+        distance += direction
+        if distance > NUM_LEDS:
+            direction = - SPEED
+        if distance < 0:
+            direction = SPEED
+
+        time.sleep(0.01)
 
 
 def hex_to_rgb(hex):