Limiting the Player: an Ammo System (Game dev Day 35)

Objective: Limit the player’s ability to fire by requiring ammo. Create both a visual and audio feedback system to alert the player of their ammo count.

Currently, the Player is free to fill the playing area with proverbial lead (lasers in our case). However, that is not indicative of refinement, and we can add a mechanic that requires the player to ration their offensive ability.

First off, we need to establish what “ammo” is to the game. We start by creating a new variable in our Player script.

Serialize the field if you want to easily change the player’s ammo from the Inspector.

Now, when do we use ammo? When we fire our laser! So if we look into our FireLaser function and determine when the player should lose ammo.

Adding onto the script from previous articles.

So now when we fire a normal shot, we subtract 1 from whatever _ammo’s current value is.

Now what happens if the player is out of ammo (or _ammo == 0)?

No projectile is fired, and we play a sound effect to alert the player to their conundrum. We need to implement a few more things to get that audio working however, so let’s tackle that next.

We need to add that _audioSource2 variable to our script, as well as the sound effect itself.

Same logic we used for the laser sound effect.

Go back to Unity and add a new Audio Source to the Player (at this point I have 3, one for laser, one for no ammo, and one for picking up a powerup).

Lots of variables here, but we only care about the bottom two right now.

Add the sound effect you want to the “No Ammo Sound Clip”, and then add it again to the new Audio Source’s AudioClip slot. It should look like the above picture.

Now we need to go back to our script and determine when this new sound should play. It will fall into the “if (_ammo == 0)” part of our FireLaser function.

Same image as before, now with context.

Great! Now the player can here a sad “clink” when they have no more ammo, but we can do better than that. Let’s add a UI element to display the current ammo count at all times so the player can better determine when to fire.

First, we need a new UI text object, and we need to place it as a child of our Canvas Gameobject (just like every other UI piece).

Next, lets change the color from grey to a bright green in the Inspector.

We will also add the beginning value of the ammo (15)

Feel free to play around with color, size, and position of the UI element. We all have our preferences.

I positioned my Ammo counter right below my score output in the game window.

Easy to see, and it stands out!

Now we just have to link everything together and add some simple math to our code.

First, we need another variable, this time in our UIManager script for the Ammo text object.

This is in the UIManager script.

Next, we need a function to change our ammo count. A simple example is as follows:

This will change the content of the UI element to match whatever math we do it.

Remember that we already have the subtraction of the ammo in our Player script. So lets add this new function to our player script right after we subtract the ammo.

The UI manager is now being called to update the ammo counter.

Last but not least, we need to drag and drop the Ammo Text object into the UIManager script’s variable for it.

Make sure you place that Ammo_Display object in the Hierarchy into the script to link it all up.

And voila! There is now visual and audio feedback alerting the player of this mechanic. A visual demonstration can be seen below.

The ammo counter goes down with each shot.

Next, shooting on 0 ammo will not produce a laser.

Pressing Space did not produce any lasers once the counter read 0.

Finally, a short video to show the new sound effect.

Listen for the no ammo sound effect.