February, 2021 | Learn C Games Programming Blog

Month: February 2021

Portable Life in C

Posted on February 28, 2021February 28, 2021 by David

I’ve mentioned Life before, this is the cellular automata as discovered by John Horton Conway. It’s perhaps less of a game and more of a recreation for anyone fascinated by programming. It’s hard to add up how many man-hours have been spent on it.

Developer Justine Tunney (aka Jart on Github) has developed a portable Life called Apelife. Portable as in it can run on Windows (graphically) and Linux (Text User Interface). The application is a modest 112 KB in size and is one of the fastest I’ve seen. When you have a large area and gliders whizz across it, you know its fast.

She is also the author of Cosmopolitan C which Apelife uses. It lets gcc outputs portable binaries that will run on every Linux distro in addition to Mac OS X, Windows NT, FreeBSD, OpenBSD, and NetBSD. It’s rather ingenious.

Added a tutorial on memory use in C

Posted on February 27, 2021February 26, 2021 by David

You can read the tutorial here. It looks at the different ways memory is used in a C program. Do you know for instance what BSS is and when it is used compared to Data or where variables in a function declared static are held in memory?

I also tried overwriting a text literal out of curiosity to see what happens. Here’s the source:

#include<stdio.h>
#include <string.h>

char* name="My name is David";
int main()
{    
    strcpy_s(name,10, "New name");
    printf("Name = %s\n", name);
    return 0;
}

As you’d expect it blew up”

Work in Progress – Web game

Posted on February 26, 2021February 24, 2021 by David

I did some investigative work on this at the weekend, This is my Inselkampf type web game. Although I know C#, I’m fairly new to ASP.NET and Blazor. Now the first thing you’ll notice about most Blazor examples on the web is that many look like the screenshot. In particular, the purple gradient down the left hand side.

So my first job was find out where that’s defined and try changing it. In the project which is Blazor WebAssembly, there’s a shared folder and it contains two .css files. MainLayout.razor.css and NavMenu.razor.css. These are the files you need to alter.

Now its probably seven or eight years since I last touched CSS and it has come on quite a bit since then. I discovered css-grid which simplifies things enormously. If you want to find out more about CSS, take a look on FreeCodeCamp.org. This site has lots of example layouts using CSS-Grid and I went for Redefining Grid Areas with Media Queries.

This lets you specify a width so you can have a responsive website which adapts to mobile phones as well as desktop. I merged the css and HTML from the example into the project and although its an early stage, I’m quite pleased with it.

This is very early. The font, colours etc will all change but this has given me a web template with round corners, header, footer and two sidebars.

If I shrink the width of the browser the two sidebars move to positions above and below the main content like this below. It would have taken a lot more effort before css-grid to do this.

Free Windows 10 VM

Posted on February 25, 2021February 23, 2021 by David

You can get a special developer enabled VM of Windows 10 for VMWare, Hyper-V, VirtualBox, and Parallels. This VM has a time limited version, expiring in April 2021 of Windows 10 (2004 version), and includes Visual Studio with the UWP, .NET desktop, and Azure workflows enabled and also includes the Windows Template Studio extension, Visual Studio Code, plus Windows Subsystem for Linux enabled with Ubuntu installed and Developer mode enabled.

It’s a 20 GB download that you can get here. The screenshot is Window 10 (fully licensed!) running under Hyper-V. I keep some old development software on it that’s a real pain to reinstall. I just have to keep it backed up and can easily copy it to my next PC. Much less hassle!

Slay Tutorial four published

Posted on February 24, 2021February 22, 2021 by David

Tutorial four of my reimagining of the game Slay continues.

This was an interesting bit of code to write, particularly setting the player hexagons. Then I tried to do too much in one go, adding the forts at the same time. I split this into separate functions.

It makes extensive use of recursion and that handy trick when you work with hexagons, the IsValidHex() function which tells you which six of the surrounding eight locations are valid. This is needed because the map is stored in a 2d array so in a 3×3 block, the centre location is surrounded by eight locations.

When you use hexagons, it’s more like a brick wall with each alternate row moved over a bit. Now every location is surrounded by six adjacent locations just like in a hexagon grid. It turns out that a very simple function can tell you which of the 8 surrounding locations are valid.

In the grid I’m using, which runs in rows horizontally either 1,3 or 5,7 cells are invalid depending on whether the row is odd or even.

Here is a normal block of 3 x 3 locations.

7 0 1
6 x 2
5 4 3

But if I slide it over by 2 characters you get this.

  7 0 1     or     7 0 1
 6 x 2               6 x 2
  5 4 3            5 4 3

So by ignoring the bold locations, you can simulate a hexagon grid.

I’ve also added Debug mode which toggles with the tab key and introduced a blockId to each hex so you can see which hexes are lumped together. In Debug mode, the BlockId is printed out over the hex as in the screenshot. I’ve used the SDL_ttf library to draw the text. It slows down the screen update by a factor of 40x but is just fast enough to do 60 frames per second.

It’s interesting that the Ubuntu code running under Hyper-V is actually a lot faster than the Windows code. As with previous tutorials, the code includes conditional compilation so it will compile and run under Windows or Linux.

Note, this code is not quite perfect. It now has three bugs:

The map generator occasionally produces a map with a 2nd smaller continent separated by one hex from the main continent.
Toggling Debug mode a lot makes it behave oddly. I thought I’d fixed that but I’m not so sure.
Some blocks of contiguous hexes (all the same colour) lack forts.

Approaching the first year anniversary

Posted on February 23, 2021February 19, 2021 by David

Skyline for David-h-bolton on GitHub — GitHub Skyline for David-H-Bolton in 2020

In answer to an email I received, yes I do write all of the blog entries, tutorials and curate the collections on here. This will be blog #365 published since Feb 29th 2020. You can see links to all posts by moving your mouse over the About Me in the top menu.

The odd looking graphic is a thing that is running on GitHub called Skyline. It shows a 3D city like model generated from your GitHub commits. Mine for 2020 is this which you can zoom in and rotate, all with your mouse. Just change the link to point to your account home page on GitHub. I think it’s quite neat and perfect timing for my first anniversary.

The slab I guess is a timeline from left to right and shows a visualisation of your commits by time period to different repositories. I have no doubts there are far more cluttered and complex skylines than mine!

An interesting project- Converting BASIC Computer Games

Posted on February 22, 2021February 19, 2021 by David

Yes it’s that book again, one I have mentioned a few times. Now there’s a project to convert all of the games from the book into C#, Java, JavaScript, Python, Ruby and VB.NET. As with all Git sites, you can download all code from the site in a zip file or individual files. So far though its very early in the project and there’s only a .BAS file in each of the subfolders for each of the games in the book. If you fancy getting involved, pick a game, a language and start coding. Sadly there’s no desire for C or C++ but that still leaves C# .

I still have this book and its sequel (More BASIC Computer games!) but to be honest I wouldn’t have bothered with most of the games in either book. They are all very much of the era (1978) which was just on the cusp of the home computer revolution and so were mostly obsolete within seven or eight years, due mainly to the terminal I/O. They’re ok for learning programming and of course you could run them in a Linux terminal.

A fabulous collection of game icons

Posted on February 21, 2021February 18, 2021 by David

These are from game-icons.net and are 512 x 512 pixels two colour icons and completely free to use so long as you give credit and include a copy of the licence or a link to it. There are over 4,000 but you can download a subset if you don’t want the lot. The download file zip file size for all of them as .png is only 33 MB.

Subsets include Animal (182), Building & Place (181), Weapon (172), Symbol & Emblem (171), Body (158), Arrow & Spear (146), GUI (140), Spike, Slash & Crack (138), Head & Face (126), Blade, Sword & Knife (126), Food (125), Liquid (122)Creature & Monster (119), Tool (117) and Board & Card (116).

What’s nice is you can have them as .svg (vector) or .png and have black on white or white on black.

They may look small when shown here but each is 512 x 512 pixels which is a lot.

Ideas for C Projects when learning it

Posted on February 20, 2021February 17, 2021 by David

Maze — Image by Gordon Johnson from Pixabay

Personally I always found the best way for me to learn a new language was to take an existing program- maybe something 500 lines or so long and completely convert it to the new language. It forces you to learn how to do things like string and file handling, organising the program, getting input and producing output and so on.

But having seen requests (on the C programming subreddit) for ideas to help someone apply their newly learnt knowledge, here’s a list of ideas of projects that are doable ion C. Nothing silly like database or operating systems!

A simple calendar. Enter a date and show the month. Bonus points if you can use past dates and show the day that a date is on. Hint. Look up Zeller’s Congruence.
Implement John Conway’s Game of Life. A cellular automaton that can be quite fascinating.
Have a go at a Snake Game. No cheating by looking at the Games Sources (link above on the top menu).
Solve the 8 Queen’s problem. Put 8 queens on a chessboard so no piece can see and attack another.
Create a maze generator. Make sure it includes at least one path from start to finish.

If you get through that lot, you go up a level and should look at this list.

More Thoughts on the Blazor game design

Posted on February 19, 2021February 19, 2021 by David

This is the latest in a series on the design of a web game based loosely on a no-longer-run game called Inselkampf. It won’t be exactly the same as the original game, I have my own ideas. To see other articles in this series, click here or on the category: Blazor on the right hand side.

There are two models with Blazor. Server and WebAssembly. Both are similar but the crucial difference is that WebAssembly can run completely standalone whereas Server needs a connection to a webserver. Server uses SignalR technology.

The danger with using the Server model is that each person playing the game implicitly creates a connection. With the WebAssembly version, there is no direct connection though it makes sense to have a connection of sorts perhaps a Restful type interface. This means running a query to fetch game data and then running update queries.

So Blazor with WebAssembly it is. Why Blazor? Because it simplifies updating controls on the page.

Looking after Time

The nature of this type of game is any construction (buildings and units) takes a finite length of time. which can range from seconds to a day or so I want to see how long before my gold mine goes up a level and so on. It’s normal to have all times countdown in the browser. This should put no strain on the server as its running in the browser. Keeping server and client in sync needs a bit of care in case someone figures out how to make the browser code run faster. Once it reaches 0, an update should be sent to the server which should do a quick comparison with its time and if shenanigans has occurred, return an update status and resync the browser to the server. The rule is “If you give em a chance to cheat- they will“.

Procuring Graphics

Much though I like the Inselkampf graphics for all the buildings, I’m not going to use theirs. It’s infringing copyright (reimagining the game is not copyright infringement BTW!) . As well as the free kenney graphics that I’ve mentioned before and various other websites such as opengameart, (shown in the screenshot) there is also the Reddit game assets subreddit so between these and some others I hope I can find what I’m looking for. My requirements are quite modest.