RoboRed Microcontroller four push button linked with four LEDs

Hello, I need help with implementing a simple Arduino program using only C code. My question is to link 4 push buttons with 4 LEDs on a RoboRed Microcontroller. Currently the LEDs are not blinking when the corresponding push button is pressed. I believe it has something to do the 'PIND' statements. Any help is appreciated.

#define LED1_PIN 4
#define LED2_PIN 5
#define LED3_PIN 6
#define LED4_PIN 7

#define SW1_PIN 0
#define SW2_PIN 1
#define SW3_PIN 2
#define SW4_PIN 3

boolean isSwPressed1;
boolean isSwPressed2;
boolean isSwPressed3;
boolean isSwPressed4;

void setup() {
// put your setup code here, to run once:
DDRD = 0xF0;
PORTD = 0x00;
Serial.println("Question 2\n");


void loop() {
// put your main code here, to run repeatedly:
if(~(PIND & 0b00000001)){
//isSwPressed1= PORTD ^ 0x01; //invert the input
PORTD |=0b00010000;

if(~(PIND & 0b00000010)){
//isSwPressed2= PORTD ^ 0x02; //invert the input
PORTD |=0b00100000;

if(~(PIND & 0b00000100)){
//isSwPressed3= PORTD ^ 0x04; //invert the input
PORTD |=0b01000000;

if(~(PIND & 0b00001000)){
//isSwPressed4= PORTD ^ 0x08; //invert the input
PORTD |=0b10000000;

//if(isSwPressed1=HIGH) PORTD |=0b00010000;
//else if(isSwPressed1=LOW) PORTD &=0b00000000;

//if(isSwPressed2=HIGH) PORTD |=0b00100000;
//else if(isSwPressed2=LOW) PORTD &=0b00000000;

//if(isSwPressed3=HIGH) PORTD |=0b01000000;
//else if(isSwPressed3=LOW) PORTD &=0b00000000;

//if(isSwPressed4=HIGH) PORTD |=0b10000000;
//else if(isSwPressed4=LOW) PORTD &=0b00000000;

Perhaps you should get just one LED working.
I haven't used PIND and PORTD before.
Why do you feel the need to use it?