Simple sidescroller game - enemy.cpp

//This example program is created by thecplusplusuy for demonstration purposes. It's a simple mario like side-scroller game:
//http://www.youtube.com/user/thecplusplusguy
//Free source, modify if you want, LGPL licence (I guess), I would be happy, if you would not delete the link
//so other people can see the tutorial
//this file is enemy.cpp a class (implementation) for the enemy.
#include "enemy.h"

enemy::enemy(SDL_Surface* img,int x,int y,int xVel,int yVel)
{
    //set the variables, nothing new
    image=img;
    box.x=x;
    box.y=y;
    box.w=image->w/2;
    box.h=image->h;
    xvel=xVel;
    yvel=yVel;
    ground=0;   //is the enemy on the ground?
    //we set the clips for the image, so we can do animation, by blittin first one part of the image, than the other one
    for(int i=0;i<2;i++)
    {
        clips[i].x=i*40;
        clips[i].y=0;
        clips[i].w=clips[i].h=40;
    }
    frame=0.0;  //initialize frame is 0
}

void enemy::show(SDL_Surface* screen)
{
    SDL_Rect tmp={box.x-coord.x,box.y,40,40};   //calculate the relative coordinate, so if the enemy at 120px coordinate and the camera
    //at 100px coordinate, than we show it on 20px coordinate
    SDL_BlitSurface(image,&clips[(int)(frame+0.5)],screen,&tmp);    //we just blit it. (int)(frame+0.5) is basically the round
}

SDL_Rect* enemy::getRect()
{
    return &box;
}

void enemy::move(std::vector<std::vector<int> >& map)
{
    //calculate the start and the end coordinate (see game.cpp)
    int start=(baseclass::coord.x-(baseclass::coord.x%baseclass::TILE_SIZE))/baseclass::TILE_SIZE-2;
    int end=(baseclass::coord.x+baseclass::coord.w+(baseclass::TILE_SIZE-(baseclass::coord.x+baseclass::coord.w)%baseclass::TILE_SIZE))/50+2;
    if(start<0)
        start=0;
    if(end>map[0].size())
        end=map[0].size();
    bool nc=0;  //if this remains 0 until the end of the loops, than we fall (no ground under the enemy)
    for(int i=0;i<map.size();i++)//go through the map
        for(int j=start;j<end;j++)
        {
            if(map[i][j]==0)
                continue;
            SDL_Rect destrect={j*50,i*50,50,50};
            if(collision(&box,&destrect))   //if there was a collision
            {
                if(destrect.y>=box.y+box.h-11)//and it'a the ground (so the tile is under the enemy)
                {
                    ground=1;   //then we don't fall any more and we are on the ground
                    yvel=0;
                    nc=1;
                }else
                    xvel=-xvel; //else change the direction in the x axis
            }
        }
    if(!nc) //if there is no ground under the enemy
        yvel=5; //than fall


    box.x+=xvel;    //just move
    box.y+=yvel;
    frame+=0.1; //and animate
    if(frame>=1.4)  //if we're at frame 3
        frame=0.0;  //set back
}