firmware for ATtiny85 capacitive touch activated LED thing, with optimizations for extremely low power consumption

Capsense-LED-thing.c

/*
 * Capsense-LED-thing.c
 *
 * Created: 9/30/2016 10:25:57 PM
 * Author : firmware for Cap Sense LED thing
 * basic flow of the program is as follows 
 * wait for Pin change interrupt on PB2 -> wake up the MCU -> PWM cycle LEDs on PB3 and PB0 go back to sleep and wait for pin change interrupt
 * interesting link: https://thewanderingengineer.com/2014/08/11/pin-change-interrupts-on-attiny85/
 * Firmware for project at: http://murli-shenoy.com/?p=606 
 */ 

#define F_CPU 8000000UL

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

uint16_t i;
volatile short ActivateHeartbeat; //gotcha! - compiler optimizes this out if not volatile 

ISR(INT0_vect){	
	ActivateHeartbeat = 1;
}

void heart_beat(){
	_delay_ms(10);
	DDRB |= (1 << DDB0)|(1 << DDB3)|(1 << DDB4);
	for(i=0; i<254; i++){
		OCR0A=i;
		OCR1B = i;
		_delay_ms(1);
	}
	for(i=0; i<254; i++){
		OCR0A=~i;
		OCR1B =~i;
		_delay_ms(1);
	}
	for(i=0; i<254; i++){
		OCR0A=i;
		OCR1B = i;
		_delay_ms(1);
	}
	DDRB &= ~((1 << DDB0)|(1 << DDB3)|(1 << DDB4));
	sleep_mode();
}

void init(){
	DDRB |= (1 << DDB0)|(1 << DDB3)|(1 << DDB4)|(1<< DDB1)|(1<<DDB5);
	PORTB |= (1<<PB4)|(1<<PB1)|(1<<PB5); //enable pull up on pb4
	DDRB &= ~(1 << DDB2);
	
	GIMSK |= (1<<INT0); //enable int0 request
	MCUCR |= (0<<ISC00); //configure INT0 to be triggered on the falling edge
	
	//init timer counter for PWM output on PB0 and PB3
	TCCR0A = 3<<COM0A0 | 3<<WGM00;
	TCCR0B = 0<<WGM02 | 3<<CS00;
	GTCCR = 1<<PWM1B | 1<<COM1B0;
	TCCR1 = 3<<COM1A0 | 7<<CS10;
	ADCSRA &= ~(1<<ADEN); //disable ADC
	ActivateHeartbeat = 0;
}

int main(void) {
	init();
	//heart_beat(); //test
	sei();
	set_sleep_mode(SLEEP_MODE_PWR_DOWN);
	sleep_enable();
	sleep_mode();
	OCR0A=255;
	OCR1B = 255;
	while(ActivateHeartbeat){
		heart_beat();
		ActivateHeartbeat = 0;
		};

}