#define __AVR_ATmega2560__
#define F_CPU 16000000UL

#include <avr/io.h>
#include <util/delay.h>
#include <stdbool.h>
#include <avr/interrupt.h>

volatile int debounce_int2 = 10;
volatile int debounce_int3 = 10;

ISR(INT2_vect) {
    if (debounce_int2) return;
    debounce_int2 = 100;
    OCR0A++;
}

ISR(INT3_vect) {
    if (debounce_int3) return;
    debounce_int3 = 100;
    OCR0A--;
}

ISR(TIMER0_COMPA_vect) {
    PORTF ^= 0b00000001;
}

void main() {
    DDRF = 0b00000001;
    DDRD = 0b00000000;
    PORTD |= 0b00001100;

    // EIMSK controls which ports can trigger interrupts
    EIMSK |= _BV(INT2) | _BV(INT3);
    // Trigger on falling edge on INT2 and INT3
    EICRA |= _BV(ISC21) | _BV(ISC31);

    TCCR0B |= _BV(CS00) | _BV(CS02); // clk/1024
    TIMSK0 |= _BV(OCIE0A);
    OCR0A = 0;

    sei();

    while(1) {
        _delay_ms(10);
        OCR0A++;
    }
}