In my player script, the CalculateMovement() method tells the player how to move and sets the boundary that causes the player to switch to the opposite side.

On line 233, I assign a variable Unity's horizontal axis from it's Input Manager. This Input Manager assigns keys of my choosing to it so I can use them to move along the horizontal axis (left/right). I chose to use the left and right arrow keys. The same thing happens on line 235 but with the vertical axis and the up & down arrrow keys instead (to move up/down). I use the horizontal and vertical variables

On line 237, the direction variable controls our direction of travel. It uses the horizontal variable as the x value and the vertical variable as the y value in this Vector3(x,y,z) to allow us to move the player both horizontally and vertically using the arrow keys. We don't need the z axis in this 2D game so we pass in 0.

"_speed" is a global variable that controls how fast the player moves and when we combine it with the Vector3 that controls the player's horizontal and vertical axes, it will apply that speed when you press the arrow keys. We also multiply this by Time.deltaTime so the player moves in real time and not game run time (which would be so fast you probably wouldn't see it move).

On line 241, I use Mathf.Clamp() to restrict the y position of the player to -3.8f and 0. Which stops the player from moving below the bottom of the screen & above the middle of the screen.

On lines 243-247, I make the player warp to the opposite side of the screen (horizontally). I use an if-else if statement to check if the player is at the far left or right(which I determined to be -10.46 & +10.46 respectively). If they are then I just reassign the position.

The player script's FireLaser() allows the player to shoot a laser. The _canFire float holds how much time you must wait before another laser can be shot. It is calculated by taking the current time the game has been running and adding my _fireRate float (set to 0.15 seconds) When a Triple Shot power up is collected, the _isTripleShotActive bool is changed to true, which then instantiates my triple shot prefab of 3 lasers when we go to fire a laser.

In this if statement we see we can only fire a laser if Time.time is greater than _canFire. So if The game was running for 2.00 seconds and _canFire was calculated to be 2.15 (2.00 game time + 0.15 from _fireRate) we can't fire a laser until the game has been running for at least 2.16 seconds.

I used a coroutine to have an enemy spawn every 3 seconds. I use the _stopSpawning bool to stop enemies from spawning when the game has ended. When the game ends, (because the player has died), I change _stopSpawning to true which will stop lines 46-55 from executing.

On line 48, Random.Range() will genertate a random x position (within the range of the screen, which I determined to be -8 to 8) for the enemy to spawn at.

Line 52 will take the newly spawned Enemy and parent it to a container object in Unity so that the hierarchy won't be cluttered with Enemy objects

The enemy attacks are very similar to the player's except that the rate at which they fire is randomized, so the player can't memorize the enemy's attack pattern.

On line 110, I am accessing an array of audio sources that are on the enemy object. I have 2 as shown below: 1 for the enemy's explosion sound and the other for it's laser sound.

On line 112 I use a prefab to instantiate the enemy's laser. That prefab I assigned is an object that holds 2 of the laser objects (also used by the player), giving the enemy a dual laser to shoot.

Since this is a 2D game, I am using Unity's OnTriggerEnter2D() method to detect & react to collisions. I used that instead of OnCollisionEnter2D() because the power up will serve as a trigger. Meaning, I don't want to apply a force on the player when the power up collides with it (if it did that, the power up would push the player back as if the power up damages the player when they collect it).

On line 47, a switch statement is used to change one of the player's bools depending on the incoming powerupID (which is determined by which power up the player collected).

When the player's laser collides with an object, the laser is destroyed first (line 156)the enemy's speed is set to 0 to stop it from moving while destroyed(line 159) the enemy's collider is destroyed (line 162), then we destroy the enemy object (line 167). The order of destruction is important because if we destroyed the enemy object first, this code is destroyed with it(because it is attached to the enemy object with the Enemy.cs script) and won't run.

On line 151, I am checking to see if the laser that collided with the enemy is an enemy laser. If it is, do nothing so that other enemies can't destroy this enemy.

On line 167, I passed in the amount of time to wait as the second argument before destroying the enemy object. This is to give the explosion animation and sound effect time to play before the enemy is destroyed.

When an enemy collides with the player, we award points to the player while also damaging them as shown in lines 129-133.

Below is some code from the Damage() method (as you saw being called above) in the Player script. The Player script has a _lives variable to tell how many lives the player has.

Line 457 makes sure the player loses a life when they take damage.

Lines 459-466 is used to show visually, the damage the player has taken. When we have 2 lives, the right engine is damaged. When we have 1 life left, the left engine is damaged. The damaged right and left engines are actually child objects to the player that are inactive by default. I set them active depending on how many lives the player has.

On lines 470-479, I am checking if the player has no lives left, and if that is true, the player is destroyed (which will also terminate this script).

My ReflectorActive() method, activates the reflector by changing the _isReflectorActive bool to true on line 559.

On lines 561-562 I am using a coroutine (which you can see in the next snippet) to wait 10 seconds and then deactivate the reflector.

On line 181 of this method it takes in the amount of lives remaining and displays a sprite on the top left of the screen to represent that. If the amount of lives is greater or equal to 4, it displays a one ship sprite followed by that number. Otherwise, it will display the 3 ship sprite if 3 lives remaining, the 2 ship sprite if 2 remain, etc.

It finds the sprite in a Sprite array I have declared as a global variable. You can see in the UI Manager component image above that this array is called "Lives Sprites" and has 5 sprites assigned to it named "no_lives","One", "Two", "Three", and "Mult".

I use multiLives variable to access the "Mult" sprite in the array and the amountOfLives variable to access the rest by passing that variable's value in as the index. After I get the number of lives to display, I access the Text object in my scene and pass that value into a string on line 190. On line 196 I set the Text object to an empty string because if I get to that line the player has under 4 lives left, so I just want to display a sprite.

In my Start() method of the UIManager script, I default the score to 0 at the beginning of the game on line 53.

On line 56, I retrieve the best score by using PlayerPrefs and display that using line 58.

PlayerPrefs stores simple data, such as the highest score, so we can display it if the player starts a new game.

The snippet below is from my UIManager script. Since I've added a co-op mode to this game, I need to check if we are playing a co-op game on line 110.

On lines 112, I switch the Game Manager's _isGameOver bool to true using it's GameOver() method. This is so we can enter the if statement in my GameManager script that lets us restart the game by pressing the "R" key. However, the actual display of the Game Over & Restart text happens in my UIManager script on lines 113-114.

On line 124 I start the coroutine that flickers the Game Over text on & off (a snippet of that is also below). I used an "endless" while loop to achieve this but the coroutine will end once we restart the game, since coroutines terminate when the scene is reloaded.

Below is the code from the Explosion.cs script. This script is attached to an object whose purpose is to play the explosion animation, sound effect and destroy itself. In the video above, after detecting collisions & destroying the asteroid, this object will be instantiated,and explodes immediately.

The explosion object has an Audio Source component and an audio clip assigned to that component. All we need to do to see & hear the explosion is get that Audio Source on line 14 and then play the audio clip on that Audio Source on line 22. I definitely like how Unity is composed of component that you can easily find and access. It makes things more organized.

On line 23, I destroy the invisible & intangible explosion object after 3 seconds. 3 seconds gives enough time for the animation & sound effect to play.