diff --git a/du4/snake.c b/du4/snake.c
new file mode 100644
index 0000000..b219c8a
--- /dev/null
+++ b/du4/snake.c
@@ -0,0 +1,96 @@
+#include <stdlib.h>
+#include "snake.h"
+
+// pridanie na zaciatok
+struct snake* add_snake(struct snake* snake, int x, int y) {
+    struct snake* head = calloc(1, sizeof(struct snake));
+    head->x = x;
+    head->y = y;
+    head->next = snake;
+    return head;
+}
+// odstranenie posledneho
+struct snake* remove_snake(struct snake* snake) {
+    if (snake == NULL) return NULL;
+
+    if (snake->next == NULL) {
+        free(snake);
+        return NULL;
+    }
+
+    struct snake* snak = snake;
+
+    while (snak->next->next != NULL) {
+        snak = snak->next;
+    }
+
+    free(snak->next);
+    snak->next = NULL;
+
+    return snake;
+}
+
+// kontrola ci bod je v hadovi
+int is_snake(struct snake* snake, int x, int y) {
+    struct snake* snak = snake;
+
+    while (snak != NULL) {
+        if (snak->x == x && snak->y == y) return 1;
+        snak = snak->next;
+    }
+
+    return 0;
+}
+
+// uvolnenie celeho hada
+void free_snake(struct snake* sn) {
+    struct snake* snak = sn;
+
+    while (snak != NULL) {
+        struct snake* next = snak->next;
+        free(snak);
+        snak = next;
+    }
+}
+
+// krok hry
+int step_state(struct state* state) {
+    int nx = state->snake->x + state->sx;
+    int ny = state->snake->y + state->sy;
+
+    // stena
+    if (nx < 0 || ny < 0 || nx >= state->width || ny >= state->height) {
+        return END_WALL;
+    }
+
+    // had
+    if (is_snake(state->snake, nx, ny)) {
+        return END_SNAKE;
+    }
+
+    // jedlo
+    for (int i = 0; i < FOOD_COUNT; i++) {
+        if (state->foodx[i] == nx && state->foody[i] == ny) {
+
+            state->foodx[i] = -1;
+            state->foody[i] = -1;
+
+            state->snake = add_snake(state->snake, nx, ny);
+
+            int je_jedlo = 0;
+            for (int j = 0; j < FOOD_COUNT; j++) {
+                if (state->foodx[j] >= 0) je_jedlo = 1;
+            }
+
+            if (!je_jedlo) return END_FOOD;
+
+            return END_CONTINUE;
+        }
+    }
+
+    // normalny pohyb
+    state->snake = add_snake(state->snake, nx, ny);
+    state->snake = remove_snake(state->snake);
+
+    return END_CONTINUE;
+}
\ No newline at end of file