8bitworkshop/presets/nes/neslib2.c

//this example shows how to set up a palette and use 8x8 HW sprites
//also shows how fast (or slow) C code is

#include "neslib.h"

//#link "tileset1.c"

// palette for balls, there are four sets for different ball colors
extern unsigned char palSprites[16];

// tile set, two planes for 4 colors
extern unsigned char TILESET[8*256];

//general purpose vars
static unsigned char i,j;
static unsigned char spr;

//total number of balls on the screen
//since there are 64 HW sprites, it is absolute max

#define BALLS_MAX       64

//balls parameters

static unsigned char ball_x[BALLS_MAX];
static unsigned char ball_y[BALLS_MAX];
static unsigned char ball_dx[BALLS_MAX];
static unsigned char ball_dy[BALLS_MAX];





void main(void)
{
	//copy tileset to RAM
	vram_write((unsigned char*)TILESET, 0x0, sizeof(TILESET));
  
        pal_spr(palSprites);//set palette for sprites
        oam_size(1);
        ppu_on_all();//enable rendering

        //initialize balls parameters

        for(i=0;i<BALLS_MAX;++i)
        {
                //starting coordinates

                ball_x[i]=rand8();
                ball_y[i]=rand8();

                //direction bits

                j=rand8();

                //horizontal speed -3..-3, excluding 0
                spr=1+(rand8()%3);
                ball_dx[i]=j&1?-spr:spr;

                //vertical speed

                spr=1+(rand8()%3);
                ball_dy[i]=j&2?-spr:spr;
        }

        
        //now the main loop

        while(1)
        {
                ppu_waitnmi();//wait for next TV frame

                spr=0;

                for(i=0;i<BALLS_MAX;++i)
                {
                        //set a sprite for current ball

                        spr=oam_spr(ball_x[i],ball_y[i],0x40,i&3,spr);//0x40 is tile number, i&3 is palette

                        //move the ball

                        ball_x[i]+=ball_dx[i];
                        ball_y[i]+=ball_dy[i];

                        //bounce the ball off the edges

                        if(ball_x[i]>=(256-8)) ball_dx[i]=-ball_dx[i];
                        if(ball_y[i]>=(240-8)) ball_dy[i]=-ball_dy[i];
                }
        }
}