AVR Freaks

so i was trying to do a simple delay_ms in attiny426, here is the code:

#include <atmel_start.h>

unsigned long millis_counter = 0;

unsigend long millis(void);
void delay_ms(unsigned long time_delay);

ISR(TCA0_OVF_vect)
{
	/* Insert your TCA overflow interrupt handling code */
	millis_counter++;

	/* The interrupt flag has to be cleared manually */
	TCA0.SINGLE.INTFLAGS = TCA_SINGLE_OVF_bm;
}

int main(void)
{
	/* Initializes MCU, drivers and middleware */
	atmel_start_init();
	sei();
	/* Replace with your application code */
	while (1) {

		delay_ms(20);

	}
}

unsigned long millis(void){
	return millis_counter;
}

void delay_ms(unsigned long time_delay)
{
	unsigned long timer_millis = millis();

	while(millis() - timer_millis < time_delay);

	PORTA_toggle_pin_level(1);
}

the timer works well but it gets stuck on while, it seems timer_millis isn't initialized as it should:

if i change delay_ms to this:

void delay_ms(unsigned long time_delay)
{

	while(true)
	{
		unsigned long timer_millis = millis();
		if(timer_millis >= time_delay)
		{
			PORTA_toggle_pin_level(1);
			millis_counter = 0;
			break;
		}
	}

}

it works as it should, but i want to avoid reseting millis_counter if possible.

this didn't work either:

void delay_ms(unsigned long time_delay)
{
	unsigned long timer_millis = millis();

	while(true)
	{
		if(millis() - timer_millis >= time_delay) break;
	}

	PORTA_toggle_pin_level(1);
}

i don't know if i'm overlooking something or what is the problem.

i atteched the project.