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

#include <stdbool.h>

#define D1	PB0
#define D2	PB1
#define D3	PB2
#define D4	PB4

#define SW1 PD2
#define SW2 PD4

int main(void) {
	// ouput pins for leds
	DDRB		 |= _BV(D4);
	DDRB		 |= _BV(D3);
	DDRB		 |= _BV(D2);
	DDRB		 |= _BV(D1);

	// set input (not neccessary since input by default)
	DDRD		 &= ~(_BV(SW1));
	DDRD		 &= ~(_BV(SW2));

	PORTB		 |= _BV(D4);

	uint8_t prev  = 0;
	uint8_t value = 0;
	while (true) {
		// lets read both button in a single byte, and keep track of that too
		uint8_t cur = (PIND & (_BV(SW1) | _BV(SW2)));
		// check for button SW1
		if (prev & (_BV(SW1)) && !(cur & (_BV(SW1)))) {
			value++;
		}
		// check for button SW2
		if (prev & (_BV(SW2)) && !(cur & (_BV(SW2)))) {
			value--;
		}
		prev = cur;

		// for each bit of the counter -> lets turn on or of the led
		if (value & 0b0001)
			PORTB |= (_BV(D1));
		else
			PORTB &= ~(_BV(D1));
		if (value & 0b0010)
			PORTB |= (_BV(D2));
		else
			PORTB &= ~(_BV(D2));
		if (value & 0b0100)
			PORTB |= (_BV(D3));
		else
			PORTB &= ~(_BV(D3));
		if (value & 0b1000)
			PORTB |= (_BV(D4));
		else
			PORTB &= ~(_BV(D4));
		_delay_ms(20);
	}
}