This sketch demonstrates how to set up and use Pin Change Interrupt to catch button presses on BlinkyTape.

button_interrupt.ino

// Example sketch for using interrupt-based button press detection
// It will check button state every 500ms and display it along with the push count
// It also sends this information over serial

#include <FastSPI_LED2.h>

#define LED_COUNT 60
struct CRGB leds[LED_COUNT];

#define LED_OUT      13
#define BUTTON_IN    10
#define ANALOG_INPUT A9
#define IO_A         7
#define IO_B         11

// Button interrupt variables and Interrupt Service Routine
volatile uint8_t button_state = 0;
volatile int button_push_count = 0;

ISR(PCINT0_vect){                        // Will be called on both pressing and releasing
  button_state = !(PINB & (1 << PINB6)); // Reading state of the PB6 (remember that HIGH == released)
  button_push_count += button_state;     // If pressed, increment push count
}

// Function to check whether the button was pressed since its last call
// If you just need to know whether the button was pressed,
// check for button_push_count and clear it if non-zero
void check_button(){
  static int last_count = 0;
  static uint8_t last_state = 0;
  
  int new_count = button_push_count;
  uint8_t new_state = button_state;
  
  if((new_count != last_count) || (new_state != last_state)){
    Serial.print("Interrupt triggered, count: ");
    Serial.print(new_count);
    Serial.print(", state: ");
    Serial.println((new_state)?"pressed":"released");
    last_count = new_count;
    last_state = new_state;
  } 
  
  for (int i = 0; i < 5; i++) {
    if(new_state){
      leds[i] = CRGB(0, 50, 0);      
    } else {
      leds[i] = CRGB(50, 0, 0);       
    }
  }
  for (int i = 5; i < LED_COUNT; i++) {
    int j = 5 + new_count%(LED_COUNT-5);
    if(i==j){
      leds[i] = CRGB(50, 50, 50);
    } else {
      leds[i] = CRGB(0, 0, 0);
    }
  }
  LEDS.show();
}

void setup()
{  
  Serial.begin(57600);
  
  LEDS.addLeds<WS2811, LED_OUT, GRB>(leds, LED_COUNT);
  LEDS.showColor(CRGB(0, 0, 0));
  LEDS.setBrightness(93); // Limit max current draw to 1A
  LEDS.show();

  pinMode(BUTTON_IN, INPUT_PULLUP);
  pinMode(ANALOG_INPUT, INPUT_PULLUP);
  pinMode(IO_A, INPUT_PULLUP);
  pinMode(IO_B, INPUT_PULLUP);
  
  // Interrupt set-up; see Atmega32u4 datasheet section 11
  PCIFR  |= (1 << PCIF0);  // Just in case, clear interrupt flag
  PCMSK0 |= (1 << PCINT6); // Set interrupt mask to the button pin (PCINT6)
  PCICR  |= (1 << PCIE0);  // Enable interrupt
}

void loop()
{
  check_button();
  delay(500);
}