基于OPENGL的简单程序，实现小球和墙的碰撞。功能：增加、减小小球半径，小球自由下落，控制小球上下左右运动，并加速。-OPENGL based on a simple procedure to achieve a small ball and wall collisions. Function: to increase, reducing the radius of the small ball, small ball free-fall, controlling the ball up an