tutorials | Learn C Games Programming Blog

Category: tutorials

Onslaught (aka Slay on Linux) tutorial two published

Posted on January 19, 2021January 17, 2021 by David

I’m quite pleased with this. It took about six hours in total to create including the time to create the graphics. Running in Hyper-V under Ubuntu 20.04, it draws a screenful of graphics in about 65 microseconds.

I took the hexagon drawing code from the AboutEmpire.zip code on GitHub and modernised it for SDL2. The Empire code uses Surfaces from SDL1 while this uses Textures from SDL2.

There are nine hexagons with all but the dark one having an internal border.

I think the orange and salmon hex look a bit too close, so I’ll change one of them.

The tutorial goes into a bit more depth. about the program (which is just over 200 lines long) and can be found on GitHub in the file Onslaught1.zip.

New Tutorial – Implementing the Windows game Slay

Posted on January 14, 2021January 14, 2021 by David

One of my favourite casual games is Slay by Sean O’Connor. I bought the full game which sells for $10 and it’s still selling well via his site or Steam. His game is only for Windows so my reimagining (great word!) will be for Linux only including Raspberry Pi.

His game comes with several hundred islands, in four sizes from very small, small, Large and very large. You play against 6 computer players with intelligence ranging from very stupid, stupid, clever to very clever. In addition there are a bunch of predefined maps like Britain or even the world.

Troops exist in four sizes with each size three times bigger than the one below. Your territory must be big enough to support the troops there and if it isn’t they all starve. Splitting an enemies’ territory to starve his troops is a valid tactic.

Add in with trees which can spread and waste land which spreads even faster and its a cute addictive game.

My game will be called Onslaught and use its own graphics. Islands will be computer generated and hopefully the AI will play a decent game. The first tutorial which just explains the game and the scope of what I intend to do is now available.

Atoms tutorial three- finishing the game off

Posted on January 13, 2021January 10, 2021 by David

I fixed the bug in the Atoms game and the third tutorial finishes it off. The source code (in this case atoms3.c) has been placed on GitHub and the final version is about 300 lines long.

As well as the bug fix, I added a line to show the number of cells owned by the player and the computer. You can see it after the player move (Player : 41 Computer 16) and after the Computer move.

This whole atoms game was an experiment to see if I can introduce C programming without having to go overboard explaining every statement etc as I’ve done in the past. I think I’ll get back to programming games!

Next atoms tutorial added

Posted on January 9, 2021January 6, 2021 by David

The first version of the program was 90 lines long but now it has grown to 275. This includes code to let the computer play and checking code plus I’ve refactored it a bit, simplifying the code. I haven’t extensively tested it and at least one bug has crept in. Occasionally the computer seems to claim ownership of a player cell. This stops you adding one to that cell so its not good.

You are welcome to have a look at the code and fix it. I will in a few days. The code is on GitHub and is a single file atoms2.c. As before its been compiled with Visual Studio 2019 Community edition though it should compile more or less unchanged with gcc, clang etc. It runs in a terminal/command line. You can see the computer playing in the screenshot.

I’ve also added the tutorial for this.

Tutorial on Atoms added

Posted on January 2, 2021January 2, 2021 by David

This is my alternative approach to learning C. Show code, explain what it does in depth rather than explaining the C language feature-by-feature. I’ve created a 90 line skeleton program for atoms. The full file is on GitHub, The file is called atoms.c.

All this does is setup the board and let you enter your move. I’ve tested it on Windows and it calls _getch() to read the keyboard so it’s fast to enter moves and you don’t have to press enter/return. It then validates the move and updates the board and draws it. No chain reactions yet or computer play but those will be in future tutorials.

In the screenshot you can see I added one atom to (3,3) and then (5,6).

The board uses three characters for each cell with atoms prefixed by P or C for player and computer. Trying to have the computer play well will be an interesting bit of programming.

First new C Tutorial has been added

Posted on December 31, 2020December 29, 2020 by David

As promised, I’ve added the first C Tutorial using the Atoms (aka Chain Reaction) game. However this is just a very easy intro to the Atoms game and doesn’t have a line of C code in it. We’ll save that for the next tutorial.

The planned tutorials for this are:

Intro to the Atoms game.
Drawing the Atoms board.
Reading the keyboard and making a move.
Handling explosions and checking if the game is over.
Programming the computer player AI.
Drawing a high-score table.

These will each include a C listing and an explanation of what the new C code does.

Thinking about future C tutorials

Posted on December 30, 2020December 29, 2020 by David

Molcules — Image by Anand Kumar from Pixabay

The tutorials I’ve done have followed a fairly “standard” model. Learn a feature, learn a new feature and so on. But what if this isn’t the best way to try and teach C?

I can’t remember how I learnt C. I’m not actually sure that I did which sounds weird but I learnt C++ nearly 28 years ago (I bought a book on C++ programming while on a weekend holiday in York). I learnt more C++ four years later when I was working on a football game. That project lasted six months and then the designer of the game decided to visit India and never came back and the whole thing fell though.

Fast forward to 2006 when I started writing the About C, C++ and C# column for about.com. Because I knew C++, I sort of knew C without explicitly having learnt it, Back then C++ was a superset of C. It still mostly is but there is the odd divergence.

This morning I was reading this thread on reddit. “What do you guys think its the best way to improve your coding?” and it got me thinking about the C tutorials. I know that I like to learn by working on small projects. Most games are too big for a tutorial (heck you can get a book out of them).

So I got to thinking, what is a simple game that would make for a good set of C tutorials? I even dug out the two books BASIC Computer games and More BASIC Computer games for inspiration. However in the end I decided on the game atoms. Here are the rules.

Rules for Atoms (aka Chain Reaction)

This takes place on an 8 x 8 board. Each turn you and then your opponent. Add 1 to any cell on the board. At the start all cells are empty with a value of 0. When you add 1 to a cell, it turns red or blue if the computer is playing. If a cell reaches 4 then it is cleared to 0 and all four cells around it (horizontal and vertical) have 1 added to them and become the player’s colour. Cells in the corner only need to reach 2 to explode while cells at edges need 3.

When there are enough atoms on the board, a chain reaction can take place and you win if your atoms replace your opponents or lose in the opposite case.

To keep the tutorials simple this will be a console game. Each cell will be blank or show the number of atoms in the cell followed by a C (for computer) or P for Player instead of colours. I’ll start the first tutorial tomorrow.

New tutorial on C loop statements published

Posted on December 29, 2020December 29, 2020 by David

Mandala loops — Image by Renate Anna Becker from Pixabay

There are four types of loop statements in C, for loops, while loops, do-while loops and goto statements. The first two are much more popular; In my Windows asteroids game, I used 54 for-loops, six while-loops, three do-while loops and no gotos.

I found the same thing in Delphi and Turbo Pascal. The only difference is that Pascal uses repeat .. until instead of do-while and I prefer repeat-until. The logic is slightly clearer I feel as well. You repeat the body of the loop until a condition becomes true. In the C do-while statement, you repeat the body of the loop as long as the condition is true.

Anyway I’ve published tutorial eleven on C loop statements. Have fun. I’ll get it added to the tutorials page shortly..

I added an if and switch tutorial

Posted on December 23, 2020December 21, 2020 by David

Teachjer and blackboard — Image by mohamed Hassan from Pixabay

The next tutorial is Simple control flow in C. This demonstrates how to do if, if else and then switch statements. These are pretty siomple concepts but they are fundamentals so you do need to know them.

One thing I didin’t show in the switch tutorial is that you can mix in labels for that real write-only code experience. It’s not a technique I recvommend which is why its NOT in the tutorial but if you promise never to use this except in the rarest of circumstances, here’s what I mean.

#include <stdio.h>

int main() {
	int a = 10;
	switch (a) {
	case 1:
	case 2:
	case 3:
	case 4:
	{
		printf("a<5\n");
		break;
	};
	case 5:
fred:
	case 6:
		printf("a ==5 or a ==6\n");
		break;
	case 7:
	case 8:
	case 9:
		printf("a <9\n");
	case 10:
	{
		printf("a=10\n");
		goto fred;
	}
	default:
		printf("a not in range 1-10\n");
		break;
	}
}

The label is the line fred: and you can see in case 10 that after printing “a=10\n”, it jumps to fred which is just after the 5 case. That does nothing and falls through to the 6 case where it prints out “a ==5 or a ==6\n”. It’s not recommended but at least now if you ever see a jump to a label in a switch statement you can be sure that the programmer was not really at the top of his or her game.

New tutorial on installing SDL on Linux

Posted on December 20, 2020December 18, 2020 by David

Well you might say, “Don’t many Linux distros have SDL installed so people can play games?” and the answer is yes but not the development files and headers, and that’s what this shows you how to do along with a simple program to test that you can compile and run.

You’ll also need clang or gcc installed but as you can do that with a simple sudo apt install clang, it’s hardly worth a tutorial on its own.

However you also need to install VS Code and the C/C++ extension. Go to the VS Code website, download the Linux x64 version and double click on it to install it. After that from a terminal type code and it’ll appear. You then need to select extensions (5th icon down the left hand side) and pick the Microsoft C/C++ extension and install it.

I’ve added a new tutorial on the Tutorials page How to Install SDL on Linux. That includes a link to a demo file (its just above the screenshot) containing all three source code files and four VS Code configuration files for VS Code.

This program is almost identical to the asteroids_ch25 file (it draws lots of random size and colour rectangles on screen) but has been upgraded for Clang 10 and also what looks like a bug with search paths. There’s an extra line in Tasks.json to include the path to the SDL2 header files or you’ll get a can’t find a particular SDL header error when you compile.

Building code with VS Code is easy to understand once you “get” how the Folder works. I always keep the .vscode folder in there with the four C/C++ JSON configuration files and all source for that whatever it is you are compiling. In the screenshot below (from WinSCP), you can see the path is /home/david/Projects/Examples and it contains the .vscode folder the three source files and demo which is the compiled code. In VS Code I opened Examples as the Folder.

The .vscode folder is greyed out because the . means it’s normally hidden.