#include <avr/io.h>
#define F_CPU 20000000
#include <util/delay.h>

int buttonState = 0;

int main(void)
{
  CPU_CCP = CCP_IOREG_gc; // Un-protect protected I/O registers - allow clock changes
  CLKCTRL_MCLKCTRLB = 0; // disable clock prescaler - clock is now equal to system clock - 20MHz

  VPORTA_DIR |= PIN7_bm; // set PA7 as ouput (LED)
  VPORTA_IN |= PIN6_bm;  // set PA4 as input (switch)

  while(1)
  {
    buttonState = VPORTA_IN & PIN6_bm; 
    // If button is not pressed
    if (buttonState > 0) {
      PORTA_OUTTGL = PIN7_bm;  // Toggle PORTA (PA7)
      _delay_ms(200); // gives delay
    }
  }
}