diff --git a/du5/snake.c b/du5/snake.c
index cc697ba..876b570 100644
--- a/du5/snake.c
+++ b/du5/snake.c
@@ -2,23 +2,85 @@
 #include <stdlib.h>
 
 struct snake* add_snake(struct snake* snake,int x,int y){
-    return NULL;
+	struct snake* head = calloc(1,sizeof(struct snake));
+	head->x = x;
+	head->y = y;
+	head->next = snake;
+	return head;
 }
 
 struct snake* remove_snake(struct snake* snake){
-    return NULL;
+    	struct snake* part = snake;
+	if (part->next == NULL) {
+		free(part);
+		return NULL;
+	}
+	else {
+		while(part->next->next != NULL) {
+			part = part->next;
+		}
+		free(part->next);
+		part->next = NULL;
+
+	}
+	return snake;
 }
 
 void free_snake(struct snake* sn){
+	struct snake* part = sn;
+	if (part != NULL) {
+		free_snake(part->next);
+		free(part);
+	}
 }
 
 int is_snake(struct snake* snake,int x,int y){
-    return 0;
+    	struct snake* part = snake;
+	do {
+		if ((part->x == x) && (part->y == y))  {
+			return 1;
+		}
+                part = part->next;
+        } while (part != NULL);
+	return 0;
 }
 
 int step_state(struct state* st){
 	int nx = (st->snake->x + st->sx);
-    int ny = (st->snake->y + st->sy);
-    return END_CONTINUE;
+    	int ny = (st->snake->y + st->sy);
+    	if (is_snake(st->snake, nx, ny)) {
+		free_snake(st->snake);
+		return END_SNAKE;
+	}
+	else {
+		int food_eaten = 0;
+		int remaining_food = 0;
+		for (int i = 0; i<FOOD_COUNT; i++) {
+			if ((st->foodx[i] == -1) || (st->foody[i] == -1)) continue;
+			if ((nx == st->foodx[i]) && (ny == st->foody[i])) {
+				st->snake = add_snake(st->snake, nx, ny);
+				food_eaten = 1;
+				st->foodx[i] = -1;
+				st->foody[i] = -1;
+			}
+			else remaining_food++;
+		}
+		if ((nx > 0) && (nx < st->width) && (ny > 0) && (ny < st->height)) {
+                        if ((!food_eaten)) {
+				st->snake = add_snake(st->snake, nx, ny);
+                   		st->snake = remove_snake(st->snake);
+			}
+		}
+		else {
+			free_snake(st->snake);
+			return END_WALL;
+		}
+		
+		if (remaining_food == 0) {
+			free_snake(st->snake);
+			return END_FOOD;
+		}
+	}
+	return END_CONTINUE;
 
 }