diff --git a/CPB_Quick_Draw_Duo/reaction.py b/CPB_Quick_Draw_Duo/reaction.py
new file mode 100644
index 000000000..3b275968b
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+++ b/CPB_Quick_Draw_Duo/reaction.py
@@ -0,0 +1,169 @@
+# cpx-reaction-timer v1.0.1
+# A human reaction timer using light and sound
+
+# Measures the time it takes for user to press the right button
+# in response to alternate first NeoPixel and beeps from onboard speaker,
+# prints times and statistics in Mu friendly format.
+
+import time
+import math
+import random
+import array
+import gc
+import board
+import digitalio
+import analogio
+import os
+
+# This code works on both CPB and CPX boards by bringing
+# in classes with same name
+try:
+    from audiocore import RawSample
+except ImportError:
+    from audioio import RawSample
+try:
+    from audioio import AudioOut
+except ImportError:
+    from audiopwmio import PWMAudioOut as AudioOut
+
+import neopixel
+
+def seed_with_noise():
+    """Set random seed based on four reads from analogue pads.
+       Disconnected pads on CPX produce slightly noisy 12bit ADC values.
+       Shuffling bits around a little to distribute that noise."""
+    a2 = analogio.AnalogIn(board.A2)
+    a3 = analogio.AnalogIn(board.A3)
+    a4 = analogio.AnalogIn(board.A4)
+    a5 = analogio.AnalogIn(board.A5)
+    random_value = ((a2.value >> 4) + (a3.value << 1) +
+                    (a4.value << 6) + (a5.value << 11))
+    for pin in (a2, a3, a4, a5):
+        pin.deinit()
+    random.seed(random_value)
+
+# Without os.urandom() the random library does not set a useful seed
+try:
+    os.urandom(4)
+except NotImplementedError:
+    seed_with_noise()
+
+# Turn the speaker on
+speaker_enable = digitalio.DigitalInOut(board.SPEAKER_ENABLE)
+speaker_enable.direction = digitalio.Direction.OUTPUT
+speaker_enable.value = True
+
+audio = AudioOut(board.SPEAKER)
+
+# Number of seconds
+SHORTEST_DELAY = 3.0
+LONGEST_DELAY = 7.0
+
+red = (40, 0, 0)
+black = (0, 0, 0)
+
+A4refhz = 440
+midpoint = 32768
+twopi = 2 * math.pi
+
+def sawtooth(angle):
+    """A sawtooth function like math.sin(angle).
+    Input of 0 returns 1.0, pi returns 0.0, 2*pi returns -1.0."""
+
+    return 1.0 - angle % twopi / twopi * 2
+
+# make a sawtooth wave between +/- each value in volumes
+# phase shifted so it starts and ends near midpoint
+vol = 32767
+sample_len = 10
+waveraw = array.array("H",
+                      [midpoint +
+                       round(vol * sawtooth((idx + 0.5) / sample_len
+                                            * twopi
+                                            + math.pi))
+                       for idx in range(sample_len)])
+
+beep = RawSample(waveraw, sample_rate=sample_len * A4refhz)
+
+# play something to get things inside audio libraries initialised
+audio.play(beep, loop=True)
+time.sleep(0.1)
+audio.stop()
+audio.play(beep)
+
+# brightness 1.0 saves memory by removing need for a second buffer
+# 10 is number of NeoPixels on CPX/CPB
+numpixels = 10
+pixels = neopixel.NeoPixel(board.NEOPIXEL, numpixels, brightness=1.0)
+
+# B is right (usb at top)
+button_right = digitalio.DigitalInOut(board.BUTTON_B)
+button_right.switch_to_input(pull=digitalio.Pull.DOWN)
+
+def wait_finger_off_and_random_delay():
+    """Ensure finger is not touching the button then execute random delay."""
+    while button_right.value:
+        pass
+    duration = (SHORTEST_DELAY +
+                random.random() * (LONGEST_DELAY - SHORTEST_DELAY))
+    time.sleep(duration)
+
+
+def update_stats(stats, test_type, test_num, duration):
+    """Update stats dict and return data in tuple for printing."""
+    stats[test_type]["values"].append(duration)
+    stats[test_type]["sum"] += duration
+    stats[test_type]["mean"] = stats[test_type]["sum"] / test_num
+
+    if test_num > 1:
+        # Calculate (sample) variance
+        var_s = (sum([(x - stats[test_type]["mean"])**2
+                      for x in stats[test_type]["values"]])
+                 / (test_num - 1))
+    else:
+        var_s = 0.0
+
+    stats[test_type]["sd_sample"] = var_s ** 0.5
+
+    return ("Trial " + str(test_num), test_type, duration,
+            stats[test_type]["mean"], stats[test_type]["sd_sample"])
+
+run = 1
+statistics = {"visual":    {"values": [], "sum": 0.0, "mean": 0.0, 
+                            "sd_sample": 0.0},
+              "auditory":  {"values": [], "sum": 0.0, "mean": 0.0, 
+                            "sd_sample": 0.0},
+              "tactile":   {"values": [], "sum": 0.0, "mean": 0.0, 
+                            "sd_sample": 0.0}}
+
+print("# Trialnumber, time, mean, standarddeviation")
+# serial console output is printed as tuple to allow Mu to graph it
+while True:
+    # Visual test using first NeoPixel
+    wait_finger_off_and_random_delay()
+    # do GC now to reduce likelihood of occurrence during reaction timing
+    gc.collect()
+    pixels[0] = red
+    start_t = time.monotonic()
+    while not button_right.value:
+        pass
+    react_t = time.monotonic()
+    reaction_dur = react_t - start_t
+    print(update_stats(statistics, "visual", run, reaction_dur))
+    pixels[0] = black
+
+    # Auditory test using onboard speaker and 444.4Hz beep
+    wait_finger_off_and_random_delay()
+    # do GC now to reduce likelihood of occurrence during reaction timing
+    gc.collect()
+    audio.play(beep, loop=True)
+    start_t = time.monotonic()
+    while not button_right.value:
+        pass
+    react_t = time.monotonic()
+    reaction_dur = react_t - start_t
+    print(update_stats(statistics, "auditory", run, reaction_dur))
+    audio.stop()
+    audio.play(beep)  # ensure speaker is left near midpoint
+
+    run += 1