The Graphical User Interface (GUI) is how your game can display information to the player. You're going to add a score to your game and make the player win or lose.

Add using UnityEngine.UI; to the top of the "Player" and "LaserClone" scripts.

Create an UI Text element (GameObject > UI > Text) and rename it "Score". In the "Score" Inspector there is a text box in the Text Script property. Change the text to "Score: 0". This also added an object to your hierarchy called a Canvas, this is where all of your GUI elements will be displayed.

Play around with the properties in the Text Scriptwith the Inspector. Make sure you change the color to something that will show up on your background (white works well) and set the Font Size to 27.

If you check the Game View you will be able to see where the score will be displayed. It's in the center, but you can move it to a better spot. Use the text element's Rect Transform in the Inspector to move the score into the corner of the screen (use the x and y values to move it into place).

Now that you have a place to display the score, you need to update the score. You want to update the score when a laser collides withan asteroid. The code that detects that collision is in the "LaserClone" script. However, you need a variable to keep track of the player's score. The score can't be put in the "LaserClone" script because it is destroyed every time the laser it is attached to is destroyed. The "Player" object is active until the end of the game, so you can store the score there.

You may have seen the keywords public and private in your time with Unity. These keywords are Access Modifiers, and they (as you probably guessed) set the access level of a type or member that they modify. If you have a variable, adding public means that any code in your project can access the variable. adding private means the variable can be only accessed from code inside of the same class. If you don't put an Access Modifier, by default they will be private.

Add to the "PlayerController" script.

public int score;

and in the void Start() function

score = 0;

Now that you have a variable to change, you can update the score in the "OnCollisionEnter()" function of the "destroyLaser" script. First you need to make sure you can get the score from the "PlayerController" script. Add PlayerController playerScript and Text displayedScore above Start(). Now add this to the 'Start()' function:

 playerScript = GameObject.Find("Player").GetComponent<PlayerController>();
 displayedScore = GameObject.Find("Score").GetComponent<Text>();

Finally, add this to the OnCollisionEnter() function:

 playerScript.score += 1;
 displayedScore.text = "Score: " + playerScript.score.ToString();

The first line is how you access the public score variable you made in the Player class. It means find the "Player" object and get the "Player script.

You access the score with the dot operator and add one to the score. displayedScore.text is the text that is displayed to the screen for the players score. ToString() just converts the score which is a number into a string so it can be displayed.

Add a new UI Text element to your canvas and call it "winOrLose". Make the text style match your score's text style, then remove all the text from the text box. Change the width of the Rect Transform to 200.

Now you are going to update the "Player" script so that it updates the "winOrLose" text based on the player losing or winning your game. Since the code will be the same for losing and winning you can create a function so that you don't have duplicate code. Add Text endgameText; above the Start() function in your "PlayerController" script. In the Start() function use endgameText = GameObject.Find("winOrLose").GetComponent<Text>(); to find the Text GameObject. Finally, Create a function with this code:

 void endGame(string text)
 {
     endgameText.text = text;
     Time.timeScale = 0;
 }

This function requires a parameter. This way you can display any text when the function is called. Time.timeScale is the speed the game is running at... setting it to 0 stops time in the game.

The last step to have your player win or lose is calling (running the code in a function) the function you just added. When the player loses is when they collide with an asteroid, so you should call the "endGame()" function in the OnCollisionEnter() function.

endGame("GAME OVER");

To make the player win, you can add an if statement in the Update() function that checks if the score is equal to a number. When the player reaches that number they will win! Add this if statement.

if (score == 10)
{
    endGame("You Win!");
}

Change 10 to whatever number you want the player to get to so that they win.

Your player can now win and lose, and they will get a message when they do!