diff --git a/src/arenas/tron/TronPlayer.php b/src/arenas/tron/TronPlayer.php
index 0a992ff..8bee942 100644
--- a/src/arenas/tron/TronPlayer.php
+++ b/src/arenas/tron/TronPlayer.php
@@ -8,21 +8,22 @@ class TronPlayer{
   
   public $isAlive = true;
     
-  public function grow($dir=""){
-    $targetCell = $this->getTargetCell($dir);
-    $this->tail[] = $targetCell;
-    return $targetCell;
+    
+  public function grow(Direction $dir){
+    //$targetCell = $this->getTargetCell($dir);
+    //$this->tail[] = $targetCell;
+    //return $targetCell;
+    $this->trail->grow($dir);
   }
   
   public function loose(){
-   
    $this->isAlive = false;
-   // $this->tail = array();
+   $this->tail->empty_tail();
     return false;
   }
   public function __make($botId, Coords $initialsCoords,$name,$url){
     $this->id = $botId;
-    $this->tail = Tail::make($initialsCoords);
+    $this->tail = Trail::make($initialsCoords);
     $this->name = $name;
     $this->url = $url; 
   }
diff --git a/src/arenas/tron/act.php b/src/arenas/tron/act.php
index d0baf84..0a32d87 100644
--- a/src/arenas/tron/act.php
+++ b/src/arenas/tron/act.php
@@ -14,6 +14,8 @@ require_once(__DIR__."/functions.php");
 require_once ("TronGame.php");
 require_once ("TronPlayer.php");
 require_once ("Direction.php");
+require_once ("Trail.php");
+require_once ("Coords.php");
 
 switch ($_POST['act']){
   case "initGame":
diff --git a/src/arenas/tron/tail.php b/src/arenas/tron/tail.php
deleted file mode 100644
index 0f45451..0000000
--- a/src/arenas/tron/tail.php
+++ /dev/null
@@ -1,31 +0,0 @@
-<?php 
-class Tail{
-  
-  public $tail;
-  
-    
-  public function __toString(){
-    $str = "";
-    foreach(Tail::$tail as $coord){
-      $str .= "[".$coord."],"; 
-    }
-    return $str;
-  }
-  
-  public function __make(Coords $InitialCoords){
-    $this->tail = array($InitialCoords);
-  }
-  
-  public function empty_tail(){
-    
-  }
-  
-  public function grow(Direction $dir){
-    $last = $this->getLastTailCoord();
-    $this->tail[] = $last->addDirection($dir);
-  }
-  
-  public function getLastTailCoord(){
-    return end(Tail::$tail);
-  }
-}
\ No newline at end of file
diff --git a/src/arenas/tron/test/TrailTest.php b/src/arenas/tron/test/TrailTest.php
new file mode 100644
index 0000000..fc3d5c0
--- /dev/null
+++ b/src/arenas/tron/test/TrailTest.php
@@ -0,0 +1,64 @@
+<?php
+use PHPUnit\Framework\TestCase;
+
+require_once '../Direction.php';
+require_once '../Coords.php';
+require_once '../TronPlayer.php';
+
+class TronPlayerTest extends TestCase {
+  public function validPlayer(Direction $direction) {
+    return new TronPlayer(
+      'http://127.0.0.1',
+      'test',
+      new Coords(0, 0),
+      $direction
+    );
+  }
+
+  public function testTronPlayerCreation() {
+    $this->assertInstanceOf(
+      TronPlayer::class,
+      $this->validPlayer(Direction::make('x+'))
+    );
+  }
+
+  public function directions() {
+    return array(
+      array(Direction::make('x+')),
+      array(Direction::make('x-')),
+      array(Direction::make('y+')),
+      array(Direction::make('y-')),
+    );
+  }
+
+  /**
+    * @dataProvider directions
+    * @expectedException OppositeForbiddenException
+    */
+  public function testOppositeForbidden(Direction $direction) {
+    $player = $this->validPlayer($direction);
+    $player->changeDirection($direction->opposite());
+  }
+
+  public function testAlreadyLost() {
+    $right = Direction::make('x+');
+    $down = Direction::make('y-');
+    $left = Direction::make('x-');
+    $up = Direction::make('y+');
+
+    $player = $this->validPlayer($right);
+    $player->nextMove($right);
+    $player->nextMove($down);
+    $player->nextMove($left);
+
+    try {
+      $player->nextMove($up);
+      throw new Exception('TronPlayer did not throw AlreadyPlayedException');
+    } catch(AlreadyPlayedException $e) { }
+
+    try {
+      $player->nextMove($up);
+      throw new Exception('TronPlayer did not throw AlreadyLostException');
+    } catch(AlreadyLostException $e) { }
+  }
+}
diff --git a/src/arenas/tron/trail.php b/src/arenas/tron/trail.php
new file mode 100644
index 0000000..874bb45
--- /dev/null
+++ b/src/arenas/tron/trail.php
@@ -0,0 +1,46 @@
+<?php
+class AlreadyBeenAddedException extends LogicException { }
+
+class Trail {
+  private $trail;
+
+  public function __construct() {
+    $this->trail = new SplStack();
+  }
+
+  public function last() {
+    return $this->trail->top();
+  }
+
+  public function add($value) {
+    if(!$this->trail->isEmpty()) {
+      if(Trail::kind($this->trail->bottom()) !== Trail::kind($value)) {
+        throw new TypeError(
+          'items added to a trail must be of the same kind'
+        );
+      }
+
+      if($this->contains($value)) {
+        throw new AlreadyBeenAddedException(
+          'value has already been added to the trail'
+        );
+      }
+    }
+
+    $this->trail->push($value);
+  }
+
+  public function contains($searchedValue) {
+    foreach($this->trail as $value) {
+      if($value == $searchedValue) return TRUE;
+    }
+
+    return FALSE;
+  }
+
+  public static function kind($var) {
+    $type = gettype($var);
+    if($type == 'object') $type .= ' ' . get_class($var);
+    return $type;
+  }
+}