Ported to CircuitPython, Tested on Gemma M0 and Trinket M0

Larson_Scanner_Shades/Larson_Scanner_Shades.ino

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+#include <Adafruit_NeoPixel.h>
+
+#define N_LEDS 22
+#define PIN     4
+
+Adafruit_NeoPixel strip = Adafruit_NeoPixel(N_LEDS, PIN, NEO_GRB + NEO_KHZ800);
+
+void setup() {
+  strip.begin();
+}
+
+int pos = 0, dir = 1; // Position, direction of "eye"
+
+void loop() {
+  int j;
+
+  // Draw 5 pixels centered on pos.  setPixelColor() will clip any
+  // pixels off the ends of the strip, we don't need to watch for that.
+  strip.setPixelColor(pos - 2, 0x100000); // Dark red
+  strip.setPixelColor(pos - 1, 0x800000); // Medium red
+  strip.setPixelColor(pos    , 0xFF3000); // Center pixel is brightest
+  strip.setPixelColor(pos + 1, 0x800000); // Medium red
+  strip.setPixelColor(pos + 2, 0x100000); // Dark red
+
+  strip.show();
+  delay(30);
+
+  // Rather than being sneaky and erasing just the tail pixel,
+  // it's easier to erase it all and draw a new one next time.
+  for(j=-2; j<= 2; j++) strip.setPixelColor(pos+j, 0);
+
+  // Bounce off ends of strip
+  pos += dir;
+  if(pos < 0) {
+    pos = 1;
+    dir = -dir;
+  } else if(pos >= strip.numPixels()) {
+    pos = strip.numPixels() - 2;
+    dir = -dir;
+  }
+}

Larson_Scanner_Shades/Larson_Scanner_Shades.py

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+import board
+import neopixel
+import time
+
+numpix = 22         # Number of NeoPixels
+pixpin = board.D1   # Pin where NeoPixels are connected Gemma M0 = D1 | Trinket M0 = D4
+strip  = neopixel.NeoPixel(pixpin, numpix, brightness=1, auto_write=False)
+pos = 0             # position
+direction = 1       # direction of "eye"
+
+while True:
+    strip[pos-2] = ([16,0,0])   # Dark red
+    strip[pos-1] = ([128,0,0])  # Medium red
+    strip[pos]   = ([255,48,0]) # brightest
+    strip[pos+1] = ([128,0,0])  # Medium red
+
+    if ( (pos + 2) < numpix ):
+        strip[pos+2] = ([16,0,0])   # Dark red, do not exceed number of pixels 
+
+    strip.write()
+    time.sleep(0.03)
+
+    # Rather than being sneaky and erasing just the tail pixel,
+    # it's easier to erase it all and draw a new one next time.
+    for j in range(-2, 2):
+        strip[pos+j] = (0,0,0)
+        if ( (pos + 2) < numpix ):
+            strip[pos+2] = (0,0,0)
+
+    # Bounce off ends of strip
+    pos += direction
+    if ( pos < 0 ):
+        pos = 1
+        direction = -direction
+    elif ( pos >= (numpix - 1) ):
+        pos = numpix - 2
+        direction = -direction

Larson_Scanner_Shades/README.md

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+# Larson_Scanner_Shades
+
+Code to accompany this tutorial:
+https://learn.adafruit.com/larson-scanner-shades