#include <stdint.h>

/* -------- Register definitions -------- */
#define DDRA  (*(volatile uint8_t*)0x21)
#define PORTA (*(volatile uint8_t*)0x22)

#define DDRB  (*(volatile uint8_t*)0x24)
#define PORTB (*(volatile uint8_t*)0x25)

/* -------- 7-segment patterns -------- */
/* (same table you already used successfully) */
uint8_t seg[10] = {
    0x3F, // 0
    0x06, // 1
    0x5B, // 2
    0x4F, // 3
    0x66, // 4
    0x6D, // 5
    0x7D, // 6
    0x07, // 7
    0x7F, // 8
    0x6F  // 9
};

/* Small delay for multiplexing */
void delay_ms(void)
{
    for (volatile uint16_t i = 0; i < 300; i++);
}

int main(void)
{
    DDRA = 0xFF;                     // segments OUTPUT
    DDRB = (1<<0)|(1<<1)|(1<<2)|(1<<3); // digit enables OUTPUT

    while (1)
    {
        /* Digit 1 → '1' */
        PORTB = 0x00;                // all digits OFF
        PORTA = seg[1];
        PORTB = (1<<0);              // enable digit 1
        delay_ms();

        /* Digit 2 → '2' */
        PORTB = 0x00;
        PORTA = seg[2];
        PORTB = (1<<1);              // enable digit 2
        delay_ms();

        /* Digit 3 → '3' */
        PORTB = 0x00;
        PORTA = seg[3];
        PORTB = (1<<2);              // enable digit 3
        delay_ms();

        /* Digit 4 → '4' */
        PORTB = 0x00;
        PORTA = seg[4];
        PORTB = (1<<3);              // enable digit 4
        delay_ms();
    }
}