var prevBallX = ballX - ballVX;
                var prevBallY = ballY - ballVY;
                var prevBrickCol = Math.floor(prevBallX / brickW);
                var prevBrickRow = Math.floor(prevBallY / brickH);


                if(prevBrickCol != ballBrickCol){
                    var adjBrickSide = rowColToArrowIndex(prevBrickCol, ballBrickRow);
                    if(!brickGrid[adjBrickSide]){
                        ballVX *= -1;
                    }
                }
                if(prevBrickRow != ballBrickRow){
                    var adjBrickTopBot = rowColToArrowIndex(ballBrickCol, prevBrickRow);
                    if(!brickGrid[adjBrickTopBot]){
                        ballVY *= -1;
                    }
                }