fliping協調時，HTML5畫布內部邊界檢測

Question

這是我的jsfiddle：http://jsfiddle.net/whZ44/1/

std1.x += std1.sp; 
if ((std1.x + std1.w) > cw) { 
    std1.x *= -std1.sp; 
} 

當塊擊中了右邊框應該翻轉x並開始移動到左邊，如果塊擊中左邊框它應該翻轉它x並向右移動。我在與代碼中的問題，我將不勝感激一些幫助

Answer 1

這現在工作：http://jsfiddle.net/whZ44/5/

var leftBorderX = 0; // set to the x value of your left border 
var newX = std1.x + std1.w; 

// if the new x value exceeds the borders (left or right) then invert the speed 
if(newX > cw || newX < leftBorderX) std1.sp *= -1; 

Answer 2

if ((std1.x + std1.w) > cw || std1.x < 0) { 
    // Invert the speed when bat reaches boundaries 
    std1.sp *= -1; 
} 

Updated fiddle