What I wanted to learn, and why it interested me: I wanted to learn how to control an LED strip because I was interested in creating colorful light effects. 

Final outcome: For my creative output, I made a rainbow flowing light effect controlled by two buttons: one button reverses the direction of the color flow, and the other switches between slow and fast speed. 

Process and reflection: 

I started by following the course tutorial and running the sample code to get the LED strip lighting up. 

I initially wanted to make two buttons control colors spreading from each end of the strip, meeting in the middle with a blended color. I ran into a frustrating problem where one of the buttons was not responding. After a lot of debugging, including checking the wiring and adding Serial Monitor tests, I confirmed the hardware was fine but the button press was being missed by the code due to timing issues with the LED strip data transmission.

I decided to change direction and made a rainbow flowing light effect instead, where one button reverses the flow direction and the other changes the speed. This experience taught me that debugging hardware and software together can be time-consuming, and that being flexible with your creative goals is an important skill. I am happy with the final result because the rainbow effect is visually satisfying and the buttons make it feel interactive.

/*

   60-223 Intro to Physical Computing, Spring 2026

   Domain-specific Skill Building: Rainbow flowing LED strip

   This sketch drives a WS2812B LED strip with a rainbow color effect.

   The colors flow continuously along the strip. One button (pin 3)

   reverses the direction of the flow, and another button (pin 4)

   toggles between slow and fast speed.

   Pin mapping:

   Arduino pin | role   | details

   --------------------------------

   2             output   LED strip data (DI)

   3             input    tactile button - reverse direction

   4             input    tactile button - toggle speed

   Coral Zhu, xiangcuz@andrew.cmu.edu

*/

#include <Adafruit_NeoPixel.h>

const int LED_DATA_PIN = 2;

const int NUM_LEDS = 30;

const int BTN_LEFT = 3;

const int BTN_RIGHT = 4;

Adafruit_NeoPixel leds(NUM_LEDS, LED_DATA_PIN, NEO_GRB + NEO_KHZ800);

int offset = 0;

int direction = 1;

int speed = 200;

bool lastBtnLeft = HIGH;

bool lastBtnRight = HIGH;

void setup() {

 pinMode(BTN_LEFT, INPUT_PULLUP);

 pinMode(BTN_RIGHT, INPUT_PULLUP);

 leds.begin();

 leds.clear();

 leds.setBrightness(50);

 leds.show();

}

void loop() {

 bool btnLeftState  = digitalRead(BTN_LEFT);

 bool btnRightState = digitalRead(BTN_RIGHT);

 if (btnLeftState == LOW && lastBtnLeft == HIGH) {

   direction = -direction;

 }

 if (btnRightState == LOW && lastBtnRight == HIGH) {

   if (speed == 100) speed = 2000;

   else speed = 100;

 }

 lastBtnLeft  = btnLeftState;

 lastBtnRight = btnRightState;

 for (int i = 0; i < NUM_LEDS; i++) {

   int hue = map(i, 0, NUM_LEDS - 1, 0, 65535) + offset;

   leds.setPixelColor(i, leds.ColorHSV(hue, 255, 255));

 }

 leds.show();

 offset += speed * direction;

 delay(20);

}