diff --git a/du4/program.c b/du4/program.c
deleted file mode 100644
index d120ffa..0000000
--- a/du4/program.c
+++ /dev/null
@@ -1,81 +0,0 @@
-#include "snake.h"
-#include <stdlib.h>
-
-static struct snake* get_tail(struct snake* snake) {
-    struct snake* tail = snake;
-    while (tail != NULL && tail->next != NULL) {
-        tail = tail->next;
-    }
-    return tail;
-}
-
-struct snake* add_snake(struct snake* snake, int x, int y) {
-    struct snake* head = calloc(1, sizeof(struct snake));
-    if (head == NULL) {
-        return snake;
-    }
-    head->x = x;
-    head->y = y;
-    head->next = snake;
-    return head;
-}
-
-struct snake* remove_snake(struct snake* snake) {
-    if (snake == NULL) {
-        return NULL;
-    }
-    if (snake->next == NULL) {
-        free(snake);
-        return NULL;
-    }
-    struct snake* prev = snake;
-    struct snake* last = snake->next;
-    while (last->next != NULL) {
-        prev = last;
-        last = last->next;
-    }
-    prev->next = NULL;
-    free(last);
-    return snake;
-}
-
-void free_snake(struct snake* sn) {
-    while (sn != NULL) {
-        struct snake* next = sn->next;
-        free(sn);
-        sn = next;
-    }
-}
-
-int is_snake(struct snake* snake, int x, int y) {
-    for (struct snake* node = snake; node != NULL; node = node->next) {
-        if (node->x == x && node->y == y) {
-            return 1;
-        }
-    }
-    return 0;
-}
-
-int step_state(struct state* st) {
-    int nx = st->snake->x + st->sx;
-    int ny = st->snake->y + st->sy;
-    int ate_food = nx == st->food_x && ny == st->food_y;
-    struct snake* tail = get_tail(st->snake);
-
-    if (nx < 0 || ny < 0 || nx >= st->width || ny >= st->height) {
-        return END_GAME;
-    }
-    if (is_snake(st->snake, nx, ny)) {
-        if (ate_food || tail == NULL || tail->x != nx || tail->y != ny) {
-            return END_GAME;
-        }
-    }
-    st->snake = add_snake(st->snake, nx, ny);
-    if (st->snake == NULL) {
-        return END_GAME;
-    }
-    if (!ate_food) {
-        st->snake = remove_snake(st->snake);
-    }
-    return END_CONTINUE;
-}
\ No newline at end of file