一棵三维L系统分型树，树枝末端是圆孔形叶子，通过拖拽或者键盘可实现树的上下左右旋转，放大缩小等功能。(A three dimensional L system parting tree, the end of the tree is a round hole leaf. Through drag and drop or keyboard, the tree can be rotated, enlarged and reduced.)