In this paper, we analyze user's manipulation and reaction in an accelerometer-based game interface, as compared with a touch joystick-based game interface. To roll the ball, the user carefully grabs and adjusts the smartphone with both hands in the accelerometer-based game interface; while the user very quickly clicks the up, down, left, right, buttons in the touch joystick-based game interface, because it is already familiar to the user. The accelerometer-based game interface is relatively more immersive and interesting than the touch joystick-based game interface; because the user gets more desired results by elaborately operating the game with both hands rather than by clicking the buttons with the thumb.