Tiny SDL framebuffer thing for Starlight

// Tiny graphics sandbox for Starlight

#include <iostream>         // For cout
#include <SDL.h>            // For SDL

using namespace std;        // So we don't have to type std::cout for cout

#define SCREEN_WIDTH 800    // How big do we want the window?
#define SCREEN_HEIGHT 600

SDL_Surface *frameBuffer;   // This is our framebuffer memory!

// Set up all SDL stuffs
void CreateSDLScreen() {
    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        cout << "Unable to init SDL: " << SDL_GetError() << endl;
        exit(1);
    }

    frameBuffer = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, 32, SDL_HWSURFACE | SDL_DOUBLEBUF);

    if (frameBuffer == NULL) {
        cout << "Unable to set up video: " << SDL_GetError() << endl;
        exit(1);
    }
    atexit(SDL_Quit);
}

// Set a pixel
void PutPixel(int x, int y, Uint32 color) {
    if(SDL_MUSTLOCK(frameBuffer))
        SDL_LockSurface(frameBuffer);
    Uint8 *pixel = (Uint8 *)frameBuffer->pixels + (y * frameBuffer->pitch) + (x * sizeof(Uint32));
    *((Uint32*)pixel) = color;
    if(SDL_MUSTLOCK(frameBuffer))
        SDL_UnlockSurface(frameBuffer);
}

// Helper function: Get correct colour value from R, G, B
Uint32 MakeColour(int r, int g, int b) {
    return SDL_MapRGB(frameBuffer->format, r, g, b);
}

// Helper function: Get a random number between 0 and some maximum
int RandomNum(int max) {
    return rand()%(max + 1);
}

// Do a l33t effect \o/
void DoEffect() {
    // Pick some random coords
    int x = RandomNum(SCREEN_WIDTH-1);
    int y = RandomNum(SCREEN_HEIGHT-1);

    // Pick a random colour
    int r = RandomNum(255);
    int g = RandomNum(255);
    int b = RandomNum(255);
    int c = MakeColour(r, g, b);

    // Set a pixel!
    PutPixel(x, y, c);
}

// Proggy entrypoint
int main (int argc, char** argv) {
    // Let's bring up SDL!
    CreateSDLScreen();

    // Flag so we know when to quit
    bool done=false;

    // Repeat until done becomes true
    while (!done) {
        // Check to see if the window's been closed and quit if so
        SDL_Event event;
        while (SDL_PollEvent(&event)) {
            if (event.type == SDL_QUIT)
                done=true;
        }

        // Draw teh leet effect!
        DoEffect();

        // Display the screen
        SDL_Flip(frameBuffer);
    }

    return 0;
}