ATtiny10. Hello World!

main.c

#define F_CPU 1000000UL

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

#define LED PB2
#define ledOn() (PORTB |= _BV(LED))
#define ledOff() (PORTB &= ~_BV(LED))

int main (void) {
    DDRB |= _BV(LED);
    PORTB &= ledOff();
    while (1)
    {
        PINB & (1 << LED) ? ledOff() : ledOn();
        _delay_ms(100);
    }
    return 0;
}

Makefile

MCU=attiny10
PROG=avrispmkii

.PHONY: all flash build download clean

all: build

flash: build download clean

build:
	avr-gcc -g -Os -mmcu=$(MCU) -c main.c && avr-gcc -g -mmcu=$(MCU) -o main.elf main.o && avr-objcopy -j .text -j .data -O ihex main.elf main.hex

download:
	avrdude -p $(MCU) -c $(PROG) -U flash:w:main.hex

clean:
	@rm -v *.hex *.o *.elf