var grid = 64;
    var max  = 50; //map is 50by50
    //set up camera
    camera          = {};
    camera.centerX  = canvas.width / 2;
    camera.centerY  = canvas.height / 2;
    camera.x        = toGrid(canvas.width/2,0,grid); //map grid x
    camera.y        = toGrid(canvas.height/2,0,grid); //map grid y
    camera.offsetX  = toWorld(camera.x,0,grid); //pixel x
    camera.offsetY  = toWorld(camera.y,0,grid); //pixel y

    function fixBoundries(x,y){
        if(x > 0 || y > 0){ //top left corner of the map works fine
            return false;
        }

        var mapRightMax = (max * grid);//map is 50 by 50 grids of 64px
        //check right max to camera center some how
        return true;
    }

    function update(e){     //called from a mouse event
        var new_mousePos    = relMouseCoords(e,this);
        var difx            = new_mousePos.x - mousePos.x,
            dify            = new_mousePos.y - mousePos.y;
        if(fixBoundries(camera.offsetX+difx, camera.offsetY+dify)){
            camera.offsetX += difx;
            camera.offsetY += dify;
        }
        camera.x = world2Grid(canvas.centerX,camera.offsetX,grid);//get grid tile x
        camera.y = world2Grid(canvas.centerY,camera.offsetY,grid);//get grid tile y
        mousePos.x = new_mousePos.x;
        mousePos.y = new_mousePos.y;
    }

    function toGrid(position,offset,grid){
        return (position*grid) + offset;
    }
    function toWorld(position,offset,grid){
        return Math.floor((position - offset) / grid);
    }