It's a mistake on iPad games to place the virtual controls on the bottom corners of the screen. The optimal place to hold an iPad is gripping the middle of each side. The controls should be easily accessible from that middle location. Holding it from the bottom is completely unnatural, unbalanced and causes your hands to get quickly fatigued. All handheld gaming systems are designed to be held on the middle of the device (PS Vita is good example). Hopefully developers will start thinking about better ergonomics when designing new iPad compatible game.