Space Invaders Clone

This readme is dated. :v

This game, as the name suggests, is yet another SpaceInvaders' clone. Obviously It's not 100% the same as the original one. But I guarantee it's good enough to be called Space Invaders Clone.

Build instructions

Linux

To start, you must install sdl2 and sdl2-mixer (in the future, when I add audio effects). If you don't know how to install those libraries, here are the commands to install them in debian, arch and fedora based distros with some extra stuff you need but might not have already installed:

1. $ sudo apt install make gcc git libsdl2-dev libsdl2-mixer-dev
2. $ sudo pacman -S make gcc git sdl2 sdl2_ttf sdl2_mixer
3. $ sudo dnf install make gcc git-all SDL2-devel SDL2_mixer-devel

Using make should produce an executable called space_invaders.out inside the repo root folder And you're done. You should be able to execute the game now.

Windows

To be documented...

Concepts

Table of Contents

1. Finite State Machines (at least two)
2. Event Loop
3. Animations
4. Keyboard and/or Mouse events
5. Timers
6. Collisions
7. Text and Images
8. Dynamic collections (at least one)
9. Something else...
10. Problems
11. The good thing

Finite State Machines

There's a total of 8 state machines that you can find in the code. Here's the diagram for each one of them:

Screens

Menu

Play

Pause

Game Over

Event Loop

Here's how I have my event loop:

void run_app_loop()
{
    const Uint32 FPS = 60;
    Uint32 start = 0, delta = 0, event_start = 0, event_wait = 1000 / FPS;

    while (screen != SCREEN_EXIT) {
        SDL_Event event;
        if (SDL_WaitEventTimeout(&event, event_wait)) {
            process_app_events(&event);

            const Uint32 event_delta = SDL_GetTicks() - event_start;
            event_start += event_delta;
            // wait less next time
            event_wait -= event_delta < event_wait ? event_delta : event_wait;
        } else {
            update_app(delta);
            render_app();
        
            delta = SDL_GetTicks() - start;
            start += delta;
            // reset event timing
            event_start = start;
            event_wait = 1000 / FPS;
        }
    }
}

Dynamic collections

First of all, a quick shout to nothings. I used two of their libraries: stb_ds.h and stb_image.h. Really good pieces of software, btw! Saved me so much hours I can't even count. There are three dynamic collections in the game: explosions, invaders and shots.

Something Else...

I was supposed to implement an algorithm, data structure or effect in my game that would make it more than just an example application implemented using all the concepts required. I came up with a technique to render texts which basically consisted in rendering ascii characters using sdl-ttf once and saving the output as a png. Then, as the font picked is almost monospaced, it became easier to map a character, say 'A', to a section of the image that contains 'A'. It helped me rendering dynamic ui elements like the score counter.

Problems

1. I couldn't figure out how to organize my code in a satisfactory way. It Probably has something to do with either my "it's not good enough" thing or my lack of knowledge on clean coding.
2. Audio effects aren't implemented yet and obviously we got some annoying bugs as well.

The good thing

Even with a lot of defects, this project helped me improve myself as a programmer and as a person. I tried so hard in the past to code simple games like pong and snake but failed. Those previous experiences made me stop thinking of game programming. However, recently I had classes on event-oriented programming with games. Those classes helped me realize I can't just start coding whatever. I need to have a goal and study on how I can reach that goal before before kicking the ball. And the bigger the project, the bigger the planning.