Switch loop direction from count-up to count-down

Also:
 - Let countdown() go negative
 - Don't update neopixels when time is negative
 - Print current time to console every update period
 - Set colormode="fill" as default in colorizer()

colorbar-fastloop.py

@@ -43,7 +43,7 @@ pixels.show()
 #   or red parameters should be set to True. Behavior when
 #   red and yellow are both set to True depends on how the
 #   colormode is configured.
-def colorizer(pxnum, colormode, yellow=False, red=False):
+def colorizer(pxnum, colormode="fill", yellow=False, red=False):
     # Every pixel from lowest to currently highest
     if colormode == "fill":
         if red:
@@ -86,8 +86,8 @@ def countdown(
     # Init the update interval tracking variable
     last_update_time = -1
 
-    # Init the elapsed time variable
+    # Init the current time variable
-    elapsed_time = 0
+    current_time = seconds
 
     # This begins what I like to call the "Are We There Yet?"
     #   loop. Instead of making the script wait for an interval
@@ -113,11 +113,13 @@ def countdown(
 
             # Loop over every pixel ID that should be lit
             #   based on the elapsed time
-            for pixel in range(round(num_pixels * (elapsed_time / seconds))):
+            for pixel in range(round(num_pixels * ((seconds - current_time) / seconds))):
                 # Set pixel color stuff
-                if elapsed_time >= seconds - redtime:
+                if current_time < 0:
+                    pass
+                elif current_time <= redtime:
                     colorizer(pixel, colormode, red=True)
-                elif elapsed_time >= seconds - yellowtime:
+                elif current_time <= yellowtime:
                     colorizer(pixel, colormode, yellow=True)
                 else:
                     colorizer(pixel, colormode)
@@ -126,4 +128,12 @@ def countdown(
             pixels.show()
 
             # Increment the elapsed time variable
-            elapsed_time += update_interval
+            current_time -= update_interval
+
+            # Massage the current_time seconds count into human-readable minutes:seconds
+            display_time = divmod(abs(current_time), 60)
+            if current_time < 0:
+                display_time_sign = "-"
+            else:
+                display_time_sign = " "
+            print("current time: " + display_time_sign + str(display_time[0]) + ":" + str(display_time[1]))

examples/neopixel-rainbow.py

@@ -0,0 +1,17 @@
+import time
+import board
+import digitalio
+import neopixel
+from adafruit_led_animation.animation.rainbow import Rainbow
+
+pixel_pin = board.GP28
+num_pixels = 1
+brightness = 0.2
+
+
+pixels = neopixel.NeoPixel(pixel_pin, num_pixels, brightness=brightness, auto_write=False)
+
+rainbow = Rainbow(pixels, 0.01, period=10)
+
+while True:
+    rainbow.animate()