Bill Morefield My thoughts, discoveries, and occasional rambiings.

The last article recreated our game loop using RLNET. We’re now going to talk a bit more about some of the design choices of RLNET so we can understand how they’ll affect our design moving forward.

First if you ran the last demo (do so now if you didn’t) you likely noticed there were two windows. Our console containing our player and a second console in the background. As our project is set as a Console Application, this console was created even though we don’t want it and don’t use it. We could get rid of the window by hiding it, but a better option in our case is to never create it. Since we’re not a console app anymore, we change our project to work as a Windows application.

Right click the project in Visual Studio’s Solution Explorer and choose Properties. Under the Application tab change the Output type to Windows Application. Save and run and you’ll see no more unwanted console window.

You’ll also notice the window looks quite a bit different now. Our Console based program had a window that was roughly in the 4×3 ratio common to Console apps. The RLNET window though is very elongated.

This is exaggerated by the use of the 2.0 scaling factor, but most comes from our change to square tiles. Most console fonts have characters that taller than they are wide. Moving to characters that are the same height as their width means that the same size window will now look shorter. For now we’ll leave it, but will come back to the window size later.

Moving to RLNET also made another change to our code that isn’t currently obvious. In our Console verion the program waited for keyboard input and then processed that input. It still appears that’s the case, but a quick test will show this is not how RLNET works. Let’s add a simple counter after our other variables.

[code language=”csharp”]
private static int tick = 0;
[/code]

We’ll add a line to print this counter to our RootConsole_Render method.

[code language=”csharp”]
_rootConsole.Print(1, 1, $"Current tick: {tick}", RLColor.White);
[/code]

Note that I’m using a recent feature of C# known as interpolated strings. If you’re not familiar with this syntax $"Current tick: {tick}" is equivalent to string.Format("Current tick: {0}", tick).

If you run the app you’ll see the tick counter increases even when we don’t press a key. That’s because the keyboard check _rootConsole.Keyboard.GetKeyPress() doesn’t wait until a key is pressed. If checks for a key press, but if no keys was pressed it continues and returns a null.

Our game loop therefore now runs in realtime. This is a change from our original game loop using the Console as the Console.ReadKey(true) command does wait until a key is pressed before continuing. It doesn’t matter here since our game does nothing at the moment, but will become more important when we add other objects to the game, especially those hostile to the player. It would be quite a surprise if the player expects a monster to move only as they do, only for it to charge across the map and attack without the player doing a thing.

That doesn’t mean that this real time aspect is a bad thing. In fact we can make a real-time loop like this operate as a turn based loop. It adds a little work on us as a programmer, but gives us flexibility for the future we can use for animations or other things we might want to occur even when there’s no action by the user.

The simplest way to move toward real time would be to loop until a key is pressed. This way the actions of the game only continue after a player action. The code would look like:

[code language=”csharp”]
RLKeyPress key;

do
{
key = _rootConsole.Keyboard.GetKeyPress();
} while (key == null);
[/code]

This won’t work. If you make this change and run the game you’ll find your game won’t respond to any keypress. What we will do instead is a more flexible approach that divides our update handler into real time and turn based components. Let’s add a second counter to track this. After the tick counter we added, add another counter.

[code language=”csharp”]
private static int turn = 0;
[/code]

and change the print statement we added earlier to also show this new counter.
[code language=”csharp”]
_rootConsole.Print(1, 1, $"Current tick: {tick} Current turn: {turn}", RLColor.White);
[/code]

Next we’ll change our Update handler to deal with the mix of events that occur every time we go through the loop (ticks) and events that we’ll process only after the player makes an action (turns).

[code language=”csharp”]
private static void RootConsole_Update(object sender, UpdateEventArgs e)
{
bool userAction = false;

// Handle keyboard input
RLKeyPress key = _rootConsole.Keyboard.GetKeyPress();
if (key != null)
{
userAction = true;
switch (key.Key)
{
case RLKey.I:
playerY -= 1;
break;

case RLKey.J:
playerX -= 1;
break;

case RLKey.M:
playerY += 1;
break;

case RLKey.K:
playerX += 1;
break;

case RLKey.Q:
_rootConsole.Close();
break;
}
}

// Turn based events only if userAction is true
if (userAction)
{
// Ensure player stays on the screen
if (playerX < 0)
playerX = 0;
if (playerX > screenWidth – 1)
playerX = screenWidth – 1;
if (playerY < 0)
playerY = 0;
if (playerY > screenHeight – 1)
playerY = screenHeight – 1;
turn++;
}

// Real time actions
tick += 1;
}
[/code]

Now running the app you’ll see the tick counter increases in real time. Our turn counter only increases when we move our character. As I originally noted, my design for this game will be turn based, that’s a purely a game design choice. Having a creature charging at the player doing nothing can be normal and expected in many games.

One last change to make today. We chose the i,j,k, and m keys out of tradition, but I think most players would be expecting the arrow keys to move the player. So let’s make a change that uses those keys for movement instead, and we’ll also let the escape key end our game.

The i, j, k, and m key arrangement dates back to the popular Unix vi editor. It therefore became rather common in software written for Unix to use these keys for cursor movement. This included Rogue and Nethack.

Change the section managing keyboard input to:

[code language=”csharp”]
if (key != null)
{
userAction = true;
switch (key.Key)
{
case RLKey.Up:
playerY -= 1;
break;

case RLKey.Left:
playerX -= 1;
break;

case RLKey.Down:
playerY += 1;
break;

case RLKey.Right:
playerX += 1;
break;

case RLKey.Q:
case RLKey.Escape:
_rootConsole.Close();
break;
}
}
[/code]

That concludes this tutorial. You can download a zip file with the code to this point. Next we’ll start giving our player something to do other than wander in empty space.

To begin the game, we’ll start with a game loop. Every game works through the same basic three steps.

1. Initialize
2. Update
3. Draw

In step one, the program sets up the inital state of the game. The game then repeats steps two and three until the game ends. To start with I’m going to build a simple Command Line project using the built in Console class in C#.

For the initial pass we’ll keep things simple. Our goal is to create a player character that can be moved around the screen with the keyboard. We’ll use the i, j, k, and m keys as in the classic Nethack to move. We’ll also use the @ character for our player, again as in Nethack (and most other text Roguelikes).

We begin by defining five variables. The first stores a flag we can set to quit the game. We also store the size of the game screen along with the player’s current position.

A C# console app begins executing our Main method here. First I add a handler function that will be called when Ctrl+C is pressed. Next we hides the cursor and then call InitializeGame() to set up he initial state of our game by setting the variables above.

The first two lines set the window and buffer size of the Console to match our specified values. We then set the initial player position to the center of the screen.

That handler code by the way just sets the quit variable to true.

Next comes the heart of the game, our game loop code.

The method begins with a while loop hat loops until the quit variable we defined earlier is true. Each pass through the loop begins with a short pause of 100ms. Given how little we’re doing at this stage of the loop, this pause keeps the pacing of our movement more controllable.

In this first pass I swapped the order of the render and update sections of the loop from above. They should occur be in the opposite order, but we’ll go with the code as written for now. These two sections repeat until we quit the game (or close the app).

The render section displays the current state of the game world and displays it to the player. Our loop begins by clearing the console giving a blank screen to draw on. Next the code prints the ‘@’ character, the player, in white at the player’s current position as specified by those variables we defined earlier.

The render section completed, the code continues to the update portion. Update handles user input and updates the game state to reflect that input.

We’re using a turn based approach and not real time. The Console.ReadKey method waits on a keypress before continuing. After the keypress, we interpret pressing the i,j,k, or m key as a request to move up, left, right, and down respectively and update the player’s position to match. We also respond to the q key by setting that quit flag to true which will end end the while loop the next time through, and thus end the game. Other keys are ignored.

After movement is processed, we check the player’s position and if the player has moved off the screen, then we shift the player back to the edge of the screen. If we didn’t do this then our game would crash with an exception when we attempted to print our character outside the defined screen. In a “real” game this check would better be done before responding to the move request.

You can download a full sample project for this simple game. Running the code as is gives us what we’d set out to accomplish. The player can move around the screen until pressing q or Ctrl-c to quit. It’s not much of a game, it’s barely even a demo, but it does give you a framework and start to build on. This basic process of update and render lies at the heart of any game.

Welcome to the first in an indefinite series of article covering my experiments creating Roguelike games using C#. I developed a renewed interest in the genre a couple years ago when I rediscovered Nethack, one of the many descendants of Rogue which gives its name to the genre of Roguelikes.

Defining a Roguelike is a bit difficult, especially as the term has come to be popular in the independent and small studio game space. There are a number of definitions proposed for Roguelikes, but .

To start I’m looking at exploring the traditional roguelike structure. The basic game here will be a single player RPG where the player controls a single character. We’ll stick with the traditional dungeon crawl setting using procedural world generation along with random distribution of creatures, items, etc. The game will be turn based, allowing the player time to consider each decision. We’ll also set the game with permadeath.

This last feature means that the player’s character dies, then the game is over. No checkpoint to start back from, no loading last save and trying again. Spend hours playing and then do something stupid and die? Too bad. It’s a harsh feature compared to many games where you can quickly save before doing almost anything.

The goal here isn’t to recreate Nethack or even necessarily produce a high quality game. I plan to write a playable and hopefully enjoyable game, but my primary goal is to learn. It’s been a while since I’ve done any type of game programming and I think this could be a fun project. I though it would be an intersting experience to document the process here and in the process also create a tutorial on build a Roguelike game in C#.

So a few decisions on what I’ll be creating. The game and tutorial will be written for Windows using C#. Most of the original Roguelike games used console graphics and I’ll do the same in this tutorial to keep things a little simpler. I’m also intentionally being a bit vague on when the program and tutorial are complete. I want to explore and try things by starting small and simple and building the program from there. I may restart any time and begin with the knowledge I’ve learned so far.

I’ll be writing this using a somewhat “warts and all” approach. I plan to document each step, misstep, and mistake. Each article will come with source code of the program implemented to that point and possibly the occasional side experiment. The code along with all displayed in the articles can be used for educational and research purposes. Feel free to use the overall code as a starting point for your own work. Please don’t simply take the code, change some words, and publish it as your own.

I’ll be using Visual Studio 2015 for development to take advantage of the newest features in C#. A few years ago I did some initial work against the console directly, but found C# support for the console too limited for what I’ll need going forward. Instead we’ll use a Console library for C#.

That’s all for this article. Next time we code.