"For"-Loop only works for final element in array

Update: After playing around with it a little, I discovered that the script seems to only work for the last element in the array. I put three blocks into the array, and even when I switched around their order, whichever one was the third element in the array would be impassible, and the others could be moved through. I still have no clue what the cause of this is.

I also moved the line...

walls = GameObject.FindGameObjectsWithTag("wall");

...into a Start() function, as some comments recommended. This doesn't seem to have changed anything, but I understand why it's better this way. Thanks in advance for any help.

Original Question:

I'm having problems with a For Loop I'm using in a custom "collision" system. I put that word in quotes because I'm implementing kind of grid-based movement, and I'm not using any physics. In my game, I have one "player" block (with dimensions 1x1x1) and multiple "wall" blocks (also with dimensions 1x1x1). The "wall" blocks are static, and the "player" block moves around by increments of 1 unit. Below, I've provided some code I wrote that detects whether the "player" block is next to a "wall" block, and sets a flag that won't allow the "player" block to move in that direction when the arrow key is pressed.

When I have one "wall" block in a scene, the script works fine, and the "player" block cannot move through it. I wanted to have more than one "wall" block, though -- in fact, I want to be able to place as many as I want and have the code apply to them automatically -- so I edited the code to iterate through all instances of "wall" blocks when determining if the "player" block was next to one. To do this, I added a "wall" tag to my "wall" block prefab, and made an array that includes all objects with that tag. This part seems to work fine -- when I start up the game, I can see all the "wall" blocks listed in the array, so they have all been detected successfully.

The problem is this: When there is more than one "wall" block in a scene, only the first "wall" block is impassible. There is no discernable difference between two "wall" blocks aside from their position, and both have the "wall" tag that includes them in the array -- which is being iterated through -- so I thought that both would be impassible. However, while the "player" block cannot move through one "wall" block, the other one allows the "player" to move straight through it, as if the code is ignoring any more than one object.

The full code is below. Any help is much appreciated!

 #pragma strict
 
 var player : Transform;
 var speed : float = 5;
 var walls : GameObject[];
 
 var right_move = true;
 var left_move = true;
 var up_move = true;
 var down_move = true;

 function Start() {

         walls = GameObject.FindGameObjectsWithTag("wall");

 }

 function Update() {

 //All this determines whether or not the "player" block is on any side of a "wall"
 //block and sets respective variables to false if it is.

     for (var wall : GameObject in walls) {
         
         if (player.position.x + 1 == wall.transform.position.x
             && player.position.z == wall.transform.position.z)
                 right_move = false;
         else right_move = true;
         
         if (player.position.x - 1 == wall.transform.position.x
             && player.position.z == wall.transform.position.z)
                 left_move = false;
         else left_move = true;
         
         if (player.position.z + 1 == wall.transform.position.z
             && player.position.x == wall.transform.position.x)
                 up_move = false;
         else up_move = true;
         
         if (player.position.z - 1 == wall.transform.position.z
             && player.position.x == wall.transform.position.x)
                 down_move = false;
         else down_move = true;
     
     }
 }    
 
 while(true) yield CoUpdate();
  
 function CoUpdate() {
 
     if (Input.GetKey(KeyCode.RightArrow)
         && right_move == true)
             yield Move(Vector3.right);
                         
     if (Input.GetKey(KeyCode.LeftArrow)
         && left_move == true)
             yield Move(Vector3.left);
                     
     if (Input.GetKey(KeyCode.UpArrow)
         && up_move == true)
             yield Move(Vector3.forward);
     
     if (Input.GetKey(KeyCode.DownArrow)
         && down_move == true)
             yield Move(Vector3.back);
                     
     else 
         yield;
 
 }
  
 function Move(distance : Vector3) {
     var pt = player.transform;
     var goal = pt.position + distance;
     while (pt.position != goal) {
         pt.position = Vector3.MoveTowards(pt.position, goal, speed * Time.deltaTime);
         yield;
     }
 }