// Included files and definitions
#define F_CPU 4000000UL	// Clock
#include <avr/io.h>		// I/O
#include <util/delay.h>	// Delay

int main(void)
{
	DDRB=0xff;	// Initializes LEDs (PORTB) as OUTPUT
	DDRD=0x00;	// Initializes Buttons (PORTD) as INPUT
	PORTB=0xff;	// Sets all LEDs to OFF as default (low-enable)
	PORTD=0xff;	// Sets all Buttons to OFF as default (low-enable)

	while(1) // Loop forever
	{
		switch(PIND) // Use Button status as a switch
		{
			case 0xfc: // SW1 = ON, SW0 = ON (LOW-Enable: 0b1111_1100)
				for (int i = 7; i >= 0; i--) // Starts at most significant bit (left) then goes to least significant (right)
				{
					PORTB = ~(1<<i); // Bit shift, then invert bits
					_delay_ms(100);  // Delay for 100ms
				}
			case 0xfe: // SW1 = ON, SW0 = OFF (LOW-Enable: 0b1111_1110)
			{
				for (int i = 7; i >= 0; i--) // Starts at most significant bit (left) then goes to least significant (right)
				{
					PORTB = ~(1<<i); // Bit shift, then invert bits
					_delay_ms(100);  // Delay for 100ms
				}
				for (int i = 0; i <= 7; i++) // Starts at least significant bit (right) then goes to most significant (left)
				{
					PORTB = ~(1<<i); // Bit shift, then invert bits
					_delay_ms(100);  // Delay for 100ms
				}
			}
			case 0xfd: // SW1 = OFF, SW0 = ON (LOW-Enable: 0b1111_1101)
				for (int i = 0; i <= 7; i++) // Starts at least significant bit (right) then goes to most significant (left)
				{
					PORTB = ~(1<<i); // Bit shift, then invert bits
					_delay_ms(100);  // Delay for 100ms
				}
			default: // ANY other button combination
			{
				PORTB = 0x55;	// 0b0101_0101
				_delay_ms(100); // Delay for 100ms
				PORTB = 0xAA;	// 0b1010_1010
				_delay_ms(100); // Delay for 100ms
			}
		}
	}
}