I remember back in the day, when computers and programming were first becoming somewhat ‘cool’. Back then, the coolest thing you could be in the computing world was a ‘hacker’. Hackers were awesome renegades who could tear down opposing systems using nothing but their superior intellect. Being able to hack was one of the best skills you could have. Now, after studying and working in computer science for a while, the term ‘hack’ has taken on a very negative connotation.

When you’re writing code, there are several things that you’re aiming for. The two broadest and most important of these are:

1. The code works – it does what you intend for it to do.
2. The code is good – it’s efficient, understandable, and easy to use/improve.

It seems like these two things would go hand-in-hand, and for well-designed code, that is often the case. However, the road to that ‘well-designed’ code is often fraught with terrible, terrible code. So, what’s the intrinsic difference between these two goals, and how does it lead to bad code?

 

Hack First, Ask Questions Later

When you’re working on a large, intricate system, and you need to add something or make a change, these two goals lead to two different types of results – a hack, or a design:

• A hack is a piece of code with only the first goal in mind – you’re just trying to ‘make it work’. You don’t want to put a lot of thought or time into the implementation, you just want it to work.
• A design has both goals in mind – you’re spending time to come up with a good solution. You’re willing to work a little harder to end up with a more robust, long-loving solution.

Designing a solution to a task leaves you with good code. It’s easy to understand, easy to use, and easy to update. The algorithm makes sense, not just in terms of “does it do what I want”, but also in terms of “does it make sense with the theory behind it”.

Looking at these two descriptions, it’s pretty easy to see – designs are better than hacks. So why would anyone ever want to use a hack to get something done? There are a few reasons.

Designs take more time. You have to come up with a solution, consider its long-term viability, consider how it will interact with every part of your system, present and future, tweak it accordingly, and make sure that it still matches the theory of your application. A hack, on the other hand, involves simply coming up with a quick and dirty solution, and implementing it.

Designs require deeper understanding. In order to fully understand the impact of your newly-designed code, you have to completely understand the current state of your application, remember all of the assumptions you made when coding it, and ensure that your new stuff won’t interfere with any existing stuff (Note that this is much harder to do on a larger team, as there are areas of the code you may not be as familiar with).

Designs are often much larger in scope. When designing a solution, it will often involve creating a ‘system’ or ‘engine’ of sorts. Not only does this take longer to think through and implement, but it also opens the door to a lot of subtle interactions between systems. Hacks are (usually) much more localized – “I’m gonna make this hack here, but I won’t use it in other places”.

You don’t want to spend a lot of effort on code that will be replaced eventually. This is really just a combination of the above points, but it’s an important reason why hacks exist. If you have to update a small piece of code, but you know that you’re going to come in and change the whole thing next month anyways, why would you put a lot of time and effort into designing a solution when a quick, hacky fix will do the trick?

 

Here’s An Example

Let’s say you’re you’re working on a pretty simple game in a pretty simple game engine, using a pretty simple programming language (hint: this means I’ll be using pseudo-code rather than real code). You’ve got your character on the screen, and you want to make him move back and forth along some flat ground whenever you hit an arrow key. You might start out with something like this:

if (keys.leftArrow) {
  dudeGuy.position.x -= 10;
}

if (keys.rightArrow) {
  dudeGuy.position.x += 10;
}

Pretty simple and straightforward – if you’re pressing the left arrow key, move your dudeGuy to the left, and if you’re pressing the right arrow key, move him to the right.

So, you use this code for your movement, and it works, and you continue working on your game. Then, suddenly, you have an epiphany – what if your dudeGuy could jump? You add a variable and hook it up:

int jumpingTimer = 0;

...

if (keys.spaceBar && jumpingTimer == 0) {
  dudeGuy.position.y += 30;
  jumpingTimer = 3;
}

if (jumpingTimer > 0) {
  dudeGuy.position.y -= 10;
  jumpingTimer--;
}

As you continue making your game, you design some levels where you realize that you want the gravity to be less strong, so you have to account for that:

float gravity = 10;

...

if (keys.spaceBar && jumpingTImer == 0) {
  dudeGuy.position.y += 30;
  jumpingTimer = 30 / gravity;
}

if (jumpingTimer > 0) {
  dudeGuy.position.y -= gravity;
  jumpingTimer--;
}

Then you realize that your back-and-forth movement looks pretty choppy, so you decide to add some ‘smoothing’, so your dudeGuy speeds up and slows down:

int movingLeftTimer = 0;
int movingRightTimer = 0;
int jumpingUpTimer = 0;
int jumpingTimer = 0;
float gravity = 10;

...

if (keys.leftArrow) {
  if (movingLeftTimer < 3) {
    movingLeftTimer++;
  }
} else if (movingLeftTimer > 0) {
  movingLeftTimer--;
}

if (movingLeftTimer > 0) {
  dudeGuy.position.x -= 10 / (4 - movingLeftTimer);
}

if (keys.rightArrow) {
  if (movingRightTimer < 3) {
    movingRightTimer++;
  }
} else if (movingRightTimer > 0) {
  movingRightTimer--;
}

if (movingRightTimer > 0) {
  dudeGuy.position.x += 10 / (4 - movingRightTimer);
}

if (keys.spaceBar && jumpingTimer == 0) {
 dudeGuy.position.y += 30;
 jumpingTimer = 30 / gravity;
}

if (jumpingTimer > 0) {
 dudeGuy.position.y -= gravity;
 jumpingTimer--;
}

And,  before you know it, with only a few changes to what we were trying to do, we end up with a piece of code that’s incredibly messy, almost impossible to understand, and prone to bugs and off-by-one errors. Honestly, I just wrote this thing, and I have no idea what it’s supposed to be doing.

Now, this example is a bit of an esoteric one, just to prove a point. However, it is definitely not the worst code I’ve ever seen (or written), and that’s saying something. What should we have written instead? Well, if you couldn’t guess, the above code is an example of a hack (or a number of hacks put together). Rather than examining what it was we needed in the long run, we repeatedly implemented something that did the job in the short term. So, let’s make a design for this use-case, and think about what we need overall.

We want to be able to move left/right, jump, have different values for gravity, and have smoothing on our movement. This sounds a bit like actual physics, so lets steal some important concepts from them – acceleration and deceleration. We’ll determine some rules that match our design, modify the dudeGuy’s acceleration in each direction based on those rules, and then move his position all at once:

float maxSpeed = 10;
float acceleration = 3;
float jumpAcceleration = 10;
float gravity = 3;
float friction = 5;
float minY = 0;

float vx = 0;
float vy = 0;

...

// If the left arrow key is down, accelerate to the left
if (keys.leftArrow) {
  vx -= acceleration;
}

// If the right arrow key is down, accelerate to the right
if (keys.rightArrow) {
  vx += acceleration;
}

// If the spacebar is down and the dudeGuy is on the ground, accelerate upwards
if (keys.spaceBar && dudeGuy.position.y == minY) {
  vy += jumpAcceleration;
}

// Accelerate downwards for gravity
vy -= gravity;

// Decelerate for friction
if (vx > 0) {
  vx -= friction;
} else if (vx < 0) {
  vx += friction;
}

// If we're going to fast to the right, slow us down to the max speed
if (vx > maxSpeed) {
  vx = maxSpeed;
}

// If we're going to fast to the left, slow us down to the max speed
if (vx < -maxSpeed) {
  vx = -maxSpeed;
}

// Update the dudeGuy's position based on our current velocity in each direction
dudeGuy.position.x += vx;
dudeGuy.position.y += vy;

// If the dudeGuy is below the ground, move him up to ground level
if (dudeGuy.position.y < minY) {
  dudeGuy.position.y = minY;
  vy = 0;
}

While we have a similar number of lines of code here, it’s much clearer what’s happening on each line. Every block serves an easy-to-understand purpose, and making changes to the ‘rules’ of movement is very easy. There are a lot of different ways to improve this code, depending on your game’s overall design, but this is a decent, and most importantly simple, place to start.

Another important feature of this piece of code is that it is well documented. Every block is pretty small, but it still has a comment describing the purpose of the block. This is an extremely important part of programming in the context of larger systems – you want to make sure that you (or anyone else) can quickly understand what your code is doing, especially in complex cases. Even though some complex logic might seem simple to you, it’ll definitely seem more difficult when you come back to it in 6 months!

 

A Necessary Evil

Unfortunately, hacks are a necessary evil. While I would love to only ever have to deal with and implement beautifully-designed code, that world doesn’t exist. There’s always a timeline, there are always changing assumptions and new features, and there’s always someone who wants it to be finished yesterday. Inevitably, you’re going to have to write some code quickly, implement a feature that’s likely to change, or come up with a simple ‘solution’ to a difficult problem. In cases like this, you’re forced to use a hack.

It’s not all bad, though. While hacks in general are pretty bad, they can be manageable if you make sure to use them correctly. In fact, I would be willing to bet that any system currently in production (of a certain size) contains quite a few hacks. There are certain qualities that hacks can have which make them a little bit more manageable, and you should try to aim for them whenever you find yourself implementing a hack:

• Understandable – It’s important that, whatever your hack is, anyone else looking at the code can understand what you were trying to do, and how your hack works. This means leaving a lot of comments around your hack, as well as simplifying the logic as much as possible.
• Localized – If you have to hack something in, you want it to only be in one place. Every time that code path is used, there’s a chance that something will go wrong. If your hack only touches a small part of your system, then its negative effects will be much less noticeable. This means that frequently-used code paths should never really have hacks in them, while hacks in rarely-used code paths are more acceptable.
• Known – This is, to me, the most important part of making a hack. If you hack something in and then forget about it, when your system starts failing, you won’t know where to look. If you make sure you remember it (by writing it down somewhere and then telling every person you know), then you’ll know where to look if something goes wrong. On top of that, you’ll always have that hack in the back of your mind, so you’ll be more likely to think of a good design to replace it.

If you follow these guidelines and make sure to try to go back and fix them, then putting hacks into your code won’t end up destroying you.

I hope this was helpful to those of you just starting out in game development – or anything which involves designing complex systems! For those of you who already know a little something about computer science, I hope this at least reinforced your burning hatred of hacks!

 

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If you want to know more about how to deal with hacky code, or what kind of hacks are in Where Shadows Slumber so that you can exploit them, feel free to contact us! You can always find out more about our game at WhereShadowsSlumber.com, find us on Twitter (@GameRevenant), Facebook, itch.io, or Twitch, and feel free to email us directly with any questions or feedback at contact@GameRevenant.com.

Jack Kelly is the head developer and designer for Where Shadows Slumber.