#include<stdint.h>

#define PIND_BASE_ADDR     0x29
int last_button_state = 1;
int led_state = 0;

typedef struct
{
  volatile uint8_t PIN;
  volatile uint8_t DDR;
  volatile uint8_t PORT;
 
}PORTD_Regs;

PORTD_Regs * pin_info = (PORTD_Regs *)PIND_BASE_ADDR; 

void setup()
{
  pin_info->DDR |= (1 << 5);
  pin_info->DDR &= ~(1 << 6);
}

void loop() 
{
  int current_button_state = (pin_info->PIN & (1 << 6)) >> 6;
  int led_state = (pin_info->PIN & (1 << 5)) >> 5;
  if(current_button_state != last_button_state)
  {
      last_button_state = current_button_state;
      if(current_button_state == 1)
      {
        if(led_state == 1)
        {
          pin_info->PORT &= ~(1<<5);
        }
        else
        {
          pin_info->PORT |= (1<<5);
        }

      }
  }
  
}