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Game Jam #2 - Van Helsing (PART 3) - Functionality

 

At the end of Part 1, we had a simplistic 2D platformer with a freely rotational gun arm that fired bullets. A good start, but there was more work to be done.

Between me and the other programmer, we split the work in two. I was in charge of the foundational gameplay and mechanics, while he was in charge of the lighting, particle systems, sound effects and other fancy stuff that you throw on top. In this log and the next, I'll be covering the remainder of the functionality I added to the game, these being: 

- Enemy damage
- Player damage & Invincibility frames
- Reloading
- The ghost
- Adding the animations created by our artist

 


 Enemy Damage

First of all: zombie damage. This was easy to add. Godot has this node called Area2D that reacts every time an object overlaps with the area that you can draw in the visual editor. This makes it really useful for multiple instances of collision detection. Every time an object enters the collision area, if the object is called "Bullet_Area2D" which is the name of the Area2D node of the bullet, then a value of 1 is removed from the health variable. When that variable reaches 0, then at this point the zombie just despawned, but that was later modified when adding the animations, so we will get to it later.

 

Player Damage & Invincibility Frames


Similarly to the zombie, when the Player's Area2D node intersects with one labelled "Zombie_Area2D" (which is obviously the zombie's) then the player loses some health. However, a variable known as "invincible" is also set to true. You might notice that the condition for taking damage from a zombie is that the colliding object is a zombie AND invincible is false. So, when invincible is set to true, the player is (surprise, surprise) invincible!

This leads us on to invincibility frames. They may not always be visible, but almost every game with enemies has them. This is for the same reason that most games give you an unfair or unrealistic advantage within the game; Being lenient with hit scans, increasing damage dealt when low on health, letting you run off an edge without immediately falling, and so on. This reason is that the primary focus of a game is to be fun and engaging. And being realistic or fair rarely delivers that experience. In fact, it can even make us feel like the game is unfair, and so to avoid this, players are buffed in ways that are subtle enough to not be noticed but impactful enough that it makes the game enjoyable.

And Van Helsing is no different. Without the invincibility frames, the player would likely lose all their health at once due to the constant collision with the zombie(s) that they cannot escape for a few milliseconds. While in (a fictitious) reality, this would accurately represent what happens when you're in a horde of zombies, it presents an unfair and irritating experience as a game, which is not our goal. As such, a small window of invincibility is created after impact that gives the player time to escape before taking damage again.

So how is it achieved? Well, using a Timer node. In Godot, this node sits dormant with a set value until it is called from a script. Upon activation, the timer counts down from the value until it reaches zero when it then runs a function in the connected script. This works well except for one small issue: if the Timer.start() function is called whilst the timer is already running, it will restart. So, I needed a way to control that line of code so that it only executed when the conditions were met (invincible = true) AND the timer is not already running. This is what the timer_active variable is. You will see many incarnations of it throughout the code, as I needed a new variable for each timer (and there are a fair few of them).

The way it works is that, upon starting the timer, timer_control is set to true so that the code cannot be run again whilst active and in the on_timer_timeout() function below, it is reset to false along with invincibility.



Reloading

Every time a bullet is fired, 1 is added to the "magazine" variable. When that variable hits 10 (10 bullets fired), the reload function initiates. This triggers a "cooldown" variable that stops bullets from being able to spawn and then starts a Timer node. Here, "timerfunc" is our timer control variable in the same way "timer_active" was for the invincibility frames. On timeout (which is the terminology used for when the timer reaches 0), cooldown and timerfunc are reset to false so the process can repeat, and magazine is returned to 0.

In this screenshot, there is a print function leftover from testing. This is something I need to work on in future projects, as there are a few of these dotted in the scripts that I forgot to clean up. Though, in an amusing twist, we later found Godot produced two exports due to this: 1 standard executable and 1 executable that launched Windows command console to print these on.

Well, this is long enough as it is so i will continue explaining my remaining involvement in the next post. 

Bye for now!
- JDM

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