#include <avr/io.h>       // For DDRx, DDxn, PORTx, PORTxn, PINx, PINxn.
#include <avr/sfr_defs.h> // For _BV(), loop_until_bit_is_clear().
#include <util/delay.h>   // For _delay_ms().

int main(void)
{
	// Configure pin direction.
	DDRD |= _BV(DDD7);    // PD7 -> output (Arduino pin 7 - yellow)
	DDRD |= _BV(DDD6);    // PD6 -> output (Arduino pin 6 - orange)
	DDRD |= _BV(DDD5);    // PD5 -> output (Arduino pin 5 - blue  )
	DDRD |= _BV(DDD4);    // PD4 -> output (Arduino pin 4 - pink  )
	DDRD &= ~(_BV(DDD2)); // PD2 -> input  (Arduino pin 2 - button)
	
	// Configure input pin pull-ups.
	PORTD |= _BV(PORTD2); // PD2 -> enabled
	                      // Button is GND when pressed, else floating.
	
	// Drive output pins low.
	PORTD &= ~(_BV(PORTD7)); // PD7 (yellow)
	PORTD &= ~(_BV(PORTD6)); // PD6 (orange)
	PORTD &= ~(_BV(PORTD5)); // PD5 (blue)
	PORTD &= ~(_BV(PORTD4)); // PD4 (pink)
	
	// Drive PD7 high (yellow).
	PORTD |= _BV(PORTD7);
	
	while (true)
	{
		// Yellow
		PORTD &= ~(_BV(PORTD6));              // Drive PD6 low  (orange)
		
		_delay_ms(200);                       // Prevent switch bounce.
		loop_until_bit_is_clear(PIND, PIND2); // Wait for button down.
		
		// Pink, Yellow
		PORTD |= _BV(PORTD4);                 // Drive PD4 high (pink)
		
		_delay_ms(200);                       // Prevent switch bounce.
		loop_until_bit_is_clear(PIND, PIND2); // Wait for button down.
		
		// Pink
		PORTD &= ~(_BV(PORTD7));              // Drive PD7 low  (yellow)
		
		_delay_ms(200);                       // Prevent switch bounce.
		loop_until_bit_is_clear(PIND, PIND2); // Wait for button down.
		
		// Blue, Pink
		PORTD |= _BV(PORTD5);                 // Drive PD5 high (blue)
		
		_delay_ms(200);                       // Prevent switch bounce.
		loop_until_bit_is_clear(PIND, PIND2); // Wait for button down.
		
		// Blue
		PORTD &= ~(_BV(PORTD4));              // Drive PD4 low  (pink)
		
		_delay_ms(200);                       // Prevent switch bounce.
		loop_until_bit_is_clear(PIND, PIND2); // Wait for button down.
		
		// Orange, Blue
		PORTD |= _BV(PORTD6);                 // Drive PD6 high (orange)
		
		_delay_ms(200);                       // Prevent switch bounce.
		loop_until_bit_is_clear(PIND, PIND2); // Wait for button down.
		
		// Orange
		PORTD &= ~(_BV(PORTD5));              // Drive PD5 low  (blue)
		
		_delay_ms(200);                       // Prevent switch bounce.
		loop_until_bit_is_clear(PIND, PIND2); // Wait for button down.
		
		// Yellow, Orange
		PORTD |= _BV(PORTD7);                 // Drive PD7 high (yellow)
		
		_delay_ms(200);                       // Prevent switch bounce.
		loop_until_bit_is_clear(PIND, PIND2); // Wait for button down.
	}
}